glp1-deepdive

GLP-1 Deep Dive

Reviewed 2026-08-09·VALEN LABS editorial·Educational reference — not medical advice
ⓘ Educational reference for laboratory reconstitution and research only. Not medical advice, not dosing instructions for human use.

GLP-1 Knowledge Base — Deep Dive Module

Tirzepatide · Semaglutide · Retatrutide

VALEN LABS — Research Peptide Intelligence (EU + Serbia · For Research Use Only)

Document purpose. This module is the deepest single reference in the VALEN LABS knowledge base for the three dominant GLP-1-class research molecules: tirzepatide, semaglutide and retatrutide. It consolidates the primary clinical evidence (NEJM / Lancet / JAMA / Nature Medicine trial programs SURMOUNT, STEP, TRIUMPH, SELECT, SURPASS, TRANSCEND), the pharmacology, official titration schedules, community / gray-market practice (r/Peptides, r/Tirzepatide, r/Semaglutide, r/Retatrutide, MesoRx, vendor guides), vial-based reconstitution and dosing protocols, the risk & compliance landscape in the US, EU and Serbia, and third-party analytical testing (Janoshik GLP-1 blind panel).

⚠️ Compliance notice. This document is an internal sales-support / research reference for a research-peptide vendor. All molecules discussed are sold strictly for laboratory research use only (RUO). Tirzepatide and semaglutide are FDA/EMA-approved human medicines; retatrutide is not approved anywhere. Nothing here is medical advice, and no claim of safety, efficacy or therapeutic use for humans is made or implied. Vendors and buyers are individually responsible for their jurisdiction's laws.

TABLE OF CONTENTS

  1. Class Overview
  2. Tirzepatide — Deep Dive
  3. Semaglutide — Deep Dive
  4. Retatrutide — Deep Dive
  5. Vial-Based Practical Protocols
  6. Side Effects, Management & Contraindications
  7. Community / Gray-Market Practice
  8. Risk & Compliance (US · EU · Serbia · RUO)
  9. Testing — Janoshik GLP-1 Blind Panel & How to Read a COA
  10. Market Context — Why GLP-1 Is the Hottest and Riskiest SKU
  11. Sources
  12. Appendix — Math, Units, Glossary

1. Class Overview & Comparison Table

1.1 What the GLP-1 "class" actually is

The incretin system is the body's own post-meal glucose-management machinery. Two gut hormones — GLP-1 (glucagon-like peptide-1) and GIP (glucose-dependent insulinotropic polypeptide) — are released after eating and amplify insulin secretion, suppress glucagon, slow gastric emptying and signal satiety to the brain. A third hormone, glucagon (GCG), is the metabolic counterweight: it mobilizes liver glycogen and fat and raises energy expenditure.

The three molecules in this module are synthetic peptide analogues engineered to hijack this system:

| Molecule | Company | Receptors | Class | Approvals (US / EU) | |---|---|---|---|---| | Semaglutide | Novo Nordisk | GLP-1 only | GLP-1 receptor agonist (GLP-1RA) | Ozempic (T2D, 2017 US / 2018 EU), Wegovy (obesity, 2021 US / 2022 EU) | | Tirzepatide | Eli Lilly | GIP + GLP-1 | Dual incretin co-agonist | Mounjaro (T2D, May 2022 US / Dec 2022 EU), Zepbound (obesity, Nov 2023 US / 2024 EU) | | Retatrutide | Eli Lilly | GIP + GLP-1 + GCG | Triple hormone receptor agonist | None. Phase 3 complete; BLA planned Q1 2027 |

The efficacy ladder (placebo-subtracted, highest dose, longest trial):

  • Semaglutide 2.4 mg: −12.4 pp at 68 weeks (STEP 1; total −14.9%)
  • Tirzepatide 15 mg: −17.8 pp at 72 weeks (SURMOUNT-1; total −20.9%)
  • Retatrutide 12 mg: −26.1 pp at 80 weeks (TRIUMPH-1; total −28.3%), up to −30.3% at 104 weeks

Each additional receptor adds metabolic horsepower — but also adds side-effect burden (especially GI and, for retatrutide, heart rate).

1.2 Head-to-head comparison table

| Parameter | Semaglutide | Tirzepatide | Retatrutide | |---|---|---|---| | Receptor targets | GLP-1R (single) | GIPR + GLP-1R (imbalanced dual) | GIPR + GLP-1R + GCGR (triple) | | Receptor potency vs native ligand | ~94% homologous to GLP-1, engineered for DPP-4 resistance | GIP-like at GIPR; biased cAMP at GLP-1R | 8.9× native GIP at GIPR; 0.3× at GCGR; 0.4× at GLP-1R | | Peptide length | 31 aa (with Aib², Arg³⁴, acylated Lys²⁶) | 39 aa | 39 aa (per Janoshik sequence) | | Half-life | ~7 days (165–168 h) | ~5 days (≈120 h) | ~6 days | | Tmax | 24–72 h | 8–72 h (median ≈24 h) | dose-proportional; ~24 h range | | Steady state | ~4–5 weeks | ~4 weeks | ~4–5 weeks | | Dosing | Once weekly SC (oral Rybelsus variant exists) | Once weekly SC | Once weekly SC | | Dose range (approved/trial) | 0.25 → 2.4 mg weekly (Wegovy); 0.25–1.0 (2.0) mg (Ozempic) | 2.5 → 15 mg weekly | 2 → 12 mg weekly (trials) | | Weight loss (headline trial) | −14.9% @ 68 wk (STEP 1) | −20.9% @ 72 wk (SURMOUNT-1) | −24.2% @ 48 wk (Ph2); −28.3% @ 80 wk (TRIUMPH-1) | | A1c lowering (T2D) | −1.9% (SUSTAIN 7, 1.0 mg) | −2.37% @ 15 mg (SURPASS-2, 40 wk) | −2.0% (TRANSCEND-T2D-1, 12 mg) | | CV outcomes | SELECT: MACE −20% (HR 0.80) | SURMOUNT CVOT in progress | TRIUMPH-3: up to −22.6% wt @ 80 wk in CVD population | | Distinctive biomarker effects | — | Strong GIP-driven fat oxidation, lipid improvements | LDL −20%, liver fat ↓, ALT ↓, resting HR ↑ ~7 bpm | | Main side-effect profile | GI (nausea ~44%) | GI (nausea ~25–30%) | GI (nausea up to ~58–60% at 12 mg), dysesthesia, HR ↑ | | Gray-market vial norm | 5 / 10 / 20 mg | 10 / 15 / 20 / 30 / 60 mg | 10 / 20 / 30 / 60 mg | | Regulatory status (2026) | Approved (US/EU); compounding restricted post-shortage | Approved (US/EU); compounding restricted post-shortage | Not approved anywhere; FDA warning letters; BLA Q1 2027 | | CAS | 910463-68-2 | 2023788-19-2 | 2381089-83-2 | | MW (Janoshik) | 4113.6 Da | 4813.5 Da | 4731.3 Da (some refs list ~4756) |

1.3 Why buyers/researchers care about the class

  1. Efficacy ceiling keeps rising. Retatrutide's 28–30% average loss approaches bariatric surgery (Roux-en-Y gastric bypass ≈ 30–35% at 1–2 years) — a pharmacological first.
  2. Chronic therapy, not a cure. Trials uniformly show weight regain on discontinuation (SURMOUNT-4: +14% in 52 weeks on placebo; STEP 4: +6.9% in 48 weeks; SELECT: ~⅔ of lost weight regained within a year of stopping). This drives lifetime demand → ideal repeat-purchase category for research-supply channels.
  3. Cost arbitrage. Branded pens run US$935–1,350/month list. Lyophilized research vials run roughly US$1–4 per mg — a 20–30× unit-price gap that explains both the compounding boom and the gray market.
  4. Maximum regulatory heat. These are the most-enforced molecules in peptide e-commerce (FDA warning letters 2025–2026, customs seizures, state AG suits, poison-center surveillance). See §8.

2. Tirzepatide — Deep Dive

2.1 Pharmacology

  • Identity. Tirzepatide (LY3298176) is a 39-amino-acid synthetic peptide engineered from the human GIP sequence, with an eicosanedioic acid (C20 fatty diacid) moiety attached via a γGlu-PEG₂-PEG₂ linker to Lys²⁰. The fatty acid binds non-covalently to serum albumin, which extends the half-life to ≈5 days and enables once-weekly dosing. Clearance ≈0.061 L/h; metabolism via peptide degradation and fatty-acid β-oxidation; excreted in urine/feces.
  • Mechanism — "imbalanced" dual agonism. Tirzepatide activates both the GIP receptor (GIPR) and the GLP-1 receptor (GLP-1R). Key nuances from structural/pharmacology papers (PNAS 2022, JCI Insight, Nat Metab 2023):
    • At the GIPR it behaves like native GIP (full, balanced agonism) — GIP agonism in adipose tissue drives fat oxidation and enhances insulin sensitivity, and is thought to be the reason tirzepatide outperforms pure GLP-1RAs.
    • At the GLP-1R it is biased: it strongly favors cAMP signaling over β-arrestin recruitment and receptor internalization — believed to reduce tachyphylaxis and improve tolerability while preserving efficacy.
    • Occupancy modelling shows greater GIPR than GLP-1R engagement at clinical doses (the molecule is GIP-preferential).
  • Effects. Glucose-dependent insulin secretion, glucagon suppression, delayed gastric emptying, central satiety, reduced food intake, increased energy expenditure (partly via GIP), improved lipid profile, ~33.9% fat-mass reduction vs ~10.9% lean-mass reduction in the SURMOUNT-1 DXA substudy (≈26% of lost weight from lean mass — the best ratio in the class).
  • Approvals.
    • US: Mounjaro (May 13, 2022, T2D); Zepbound (Nov 8, 2023, obesity BMI ≥30 or ≥27+comorbidity).
    • EU: Mounjaro T2D (Dec 2022); weight-management indication (CHMP positive Nov 10, 2023 → EC approval; EU label covers obesity and overweight-with-comorbidity); Dec 11, 2025 CHMP positive opinion extending T2D indication to children ≥10 y.
    • Serum: Ozempic/Mounjaro-adjacent availability via ALIMS; see §8.3.

2.2 Clinical trial program — SURMOUNT (obesity) + SURPASS (T2D) with numbers

SURMOUNT-1 (Jastreboff et al., NEJM 2022; NCT04184622)

  • 2,539 adults (BMI ≥30, or ≥27 with comorbidity; no diabetes), 1:1:1:1 → tirz 5/10/15 mg or placebo, 72 weeks, plus lifestyle counseling.
  • Treatment-regimen estimand (primary): −15.0% (5 mg), −19.5% (10 mg), −20.9% (15 mg) vs −3.1% placebo (p<0.001 for all).
  • Efficacy estimand: −16.0% (16.1 kg), −21.4% (22.2 kg), −22.5% (23.6 kg) vs −2.4%.
  • ≥5% loss: 85% / 89% / 91% vs 35%. ≥20% loss: 50% (10 mg) and 57% (15 mg) vs 3%.
  • ≥25% loss (exploratory): 15% / 32% / 36% vs ~0%.
  • DXA substudy (n≈124): fat mass −33.9%, lean mass −10.9% → ~26% of loss is lean.
  • Discontinuation for AE: 4.3–7.1% (dose-dependent) vs 2.6% placebo.

SURMOUNT-2 (Garvey et al., Lancet 2023) — obesity + T2D

  • 938 adults (BMI ≥27 + T2D): 10 mg, 15 mg, placebo × 72 weeks.
  • Weight: −12.8% (10 mg), −14.7% (15 mg) vs −3.2% placebo.
  • A1c: −2.1% in both tirz arms (from ~8.0% to ~5.9%); 49% reached normal A1c <5.7% without severe hypoglycemia; up to 86.9% reached A1c <7%.
  • ≥5% loss: 79–83% vs 32%; ≥15%: up to 48%; ≥20%: up to 31% (15 mg).

SURMOUNT-3 (Wadden et al., Nature Medicine 2023)

  • 12-week intensive lifestyle run-in (all arms), then 72 weeks tirz 10/15 mg vs placebo.
  • From randomization to week 72: −18.4% (tirz) vs +2.5% (placebo regain) — i.e. total from baseline ≈ −21.1%. Placebo-subtracted −20.8 pp.

SURMOUNT-4 (Aronne et al., JAMA 2024) — maintenance / rebound

  • 36-week open-label lead-in on tirz (2.5 → 15 mg, max tolerated 10 or 15 mg): mean −20.9%.
  • Then 52-week double-blind: continued tirz −5.5% more; switched-to-placebo +14.0% regain.
  • 89.5% of continued-tirz participants maintained ≥80% of lead-in loss vs 16.6% of placebo.

SURMOUNT-5 (Lilly, Dec 2024 topline; 2025 publication) — head-to-head vs semaglutide

  • 751 adults, 72 weeks: tirzepatide 15 mg vs semaglutide 2.4 mg.
  • −20.2% vs −13.7% (treatment-regimen estimand; −20.3% vs −14.4% efficacy estimand).
  • ≥25% loss: 47.5% vs 22.8%. ≥5%: 94.4% vs 92.7%.

SURMOUNT-ON (Lilly, ADA 2025) — monthly maintenance

  • After weekly titration, monthly dosing (15 mg every 4 weeks) maintained ~93% of weight loss over the maintenance period — the anchor for "maintenance = 15 mg once monthly" conversations.

SURPASS-2 (Frias et al., NEJM 2021) — T2D vs semaglutide 1 mg, 40 weeks

  • A1c: −2.01% / −2.24% / −2.37% (5/10/15 mg) vs −1.86% (sema 1 mg); placebo-adjusted −1.87 to −2.07%.
  • Weight: −7.8 / −10.3 / −12.4 kg vs −5.7 kg (sema).

Other program notes

  • SURPASS-4 (T2D + CV risk, 52 wk): A1c −2.43% (15 mg).
  • SURMOUNT-1 3-year extension: weight loss largely sustained with continued therapy.
  • SUMMIT (2025): tirzepatide in heart failure with preserved ejection fraction (HFpEF) + obesity — improved HF outcomes (CV death / HF events composite) — a landmark for the class.

2.3 Official titration — tirzepatide (Zepbound/Mounjaro weight-management label)

| Weeks | Weekly dose | Notes | |---|---|---| | 1–4 | 2.5 mg | Starting dose; no efficacy expectation — it is a tolerability ramp | | 5–8 | 5.0 mg | First therapeutic maintenance option | | 9–12 | 7.5 mg | | | 13–16 | 10 mg | Max dose studied in SURMOUNT-2 diabetic arm; common max | | 17–20 | 12.5 mg | | | 21+ | 15 mg | Maximum; 16–20 weeks to reach | | Maintenance | 5–15 mg weekly, or 15 mg monthly (SURMOUNT-ON) | Lowest dose that holds weight; some taper to 2.5 mg |

Titration is +2.5 mg every 4 weeks regardless of dose form. If a patient (or researcher's model) is intolerant, the label supports staying longer at a given dose or skipping one dose; do not double up.

2.4 Community / gray-market tirzepatide protocols (see also §7)

  • Standard trail: mirror the label — 2.5 → 5 → 7.5 → 10 mg; most community users never exceed 10 mg.
  • Microdosing / low-dose: 1.25–2.5 mg weekly (or 1.25 mg ×2/week) for appetite control with minimal sides; popular among already-lean users (research-context "recomp" use).
  • Split dosing: half the weekly dose every 3.5 days (e.g., 2.5 mg Mon + 2.5 mg Thu) to smooth the peak and cut nausea; supported by the 5-day half-life.
  • Every-5-days dosing: some users compress to q5d for a higher average concentration — NOT label dosing; increases side-effect risk.
  • Maintenance / taper: drop to 2.5–5 mg weekly, or 5 mg every 10–14 days, then reassess; the goal is finding the lowest dose that prevents regain (see SURMOUNT-4 rebound data).
  • Stacking: commonly combined with retatrutide (Reta+Tirz), tesofensine, AOD-9604, CJC/Ipamorelin — evidence-free; increases AE risk (see §7.6).

2.5 Tirzepatide side-effect highlights (SURMOUNT-1 rates)

| AE | Tirzepatide (pooled/dose) | Placebo | |---|---|---| | Nausea | 24.6% (up to ~29% at 15 mg) | 9.5% | | Diarrhea | 21.7% | 9.9% | | Constipation | 18.7% | 7.8% | | Vomiting | 8.9% | 3.5% | | Discontinuation for AE | 4.3–7.1% | 2.6% | | Cholelithiasis | 1.6% | 0.7% | | Cholecystitis | 0.6% | 0.3% | | Heart rate | +2–4 bpm | ~0 | | Hypoglycemia | rare (no insulin/sulfonylurea) | — |

3. Semaglutide — Deep Dive

3.1 Pharmacology

  • Identity. Semaglutide is a 31-amino-acid GLP-1 analogue with 94% homology to native human GLP-1. Engineering: Ala→Aib (α-aminoisobutyric acid) substitution at position 2 (DPP-4 resistance), Arg³⁴ substitution, and Lys²⁶ acylated with a C18 fatty diacid (octadecanedioic acid) via a glutamic-acid spacer — the fatty acid binds albumin, giving a ~7-day half-life (165–168 h) and once-weekly SC dosing. An oral formulation (Rybelsus 3/7/14 mg) uses the SNAC absorption enhancer (not relevant to vials).
  • Mechanism. Pure GLP-1R agonism: glucose-dependent insulin release, glucagon suppression, slowed gastric emptying, central (hypothalamic, hindbrain GLP-1R) appetite suppression. Does not activate GIPR or GCGR — the "single-receptor" benchmark against which duals and triples are measured.
  • Approvals.
    • US: Ozempic (Dec 2017, T2D; 2.0 mg dose added later); Wegovy (June 2021, obesity BMI ≥30 / ≥27+comorbidity). Wegovy HD 7.2 mg in trials/rollout 2025–2026.
    • EU: Ozempic (2018), Wegovy (Jan 2022).
    • SELECT label expansion (US 2024): reduces risk of MACE in overweight/obese adults with established CVD — the first weight-management drug with a CV-outcomes claim.
  • Half-life note for researchers. ~1 week means true steady state only after 4–5 weeks; the first 4 weeks (0.25 mg) produce minimal measurable effect — this is by design and frequently misunderstood ("it's not working" → don't escalate faster than label).

3.2 Clinical trial program — STEP (obesity) + SELECT (CV) with numbers

STEP 1 (Wilding et al., NEJM 2021) — the pivotal

  • 1,961 adults (BMI ≥30, or ≥27 + comorbidity; no diabetes), 2:1 → semaglutide 2.4 mg or placebo, 68 weeks + lifestyle.
  • −14.9% vs −2.4% (treatment difference −12.4 pp; 95% CI −13.4 to −11.5).
  • ≥5%: 86.4% vs 31.5%; ≥10%: 69.1% vs 12.0%; ≥15%: 50.5% vs ~5%.
  • Mean absolute loss 15.3 kg vs 2.6 kg.
  • DXA subset (n=95): lean soft tissue −6.9 kg (≈13%), fat mass −10.4 kg (≈25%) → ≈40% of weight lost as lean tissue (worst ratio of the three molecules — see §6.5).
  • Discontinuation for AE: 7.0% vs 3.1%. Nausea 44.2%, diarrhea 29.9%, vomiting 24.8%, constipation 24.8%.

STEP 2 (Davies et al., Lancet 2021) — T2D

  • 1,210 adults (BMI ≥27 + T2D): sema 2.4 mg vs sema 1.0 mg vs placebo × 68 weeks.
  • −9.6% (2.4 mg) / −7.0% (1.0 mg) / −3.4% placebo. ≥5%: 68.8% vs 28.5%.

STEP 3 (Wadden et al., JAMA 2021) — plus intensive behavioral therapy

  • 611 adults; both arms got 30 dietitian visits + initial 8-week low-calorie diet (1,000–1,200 kcal/day) + exercise ramp to 200 min/week.
  • −16.0% vs −5.7% at 68 weeks. ≥15%: 55.8% vs 13.2%.

STEP 4 (Rubino et al., JAMA 2021) — maintenance / withdrawal

  • 20-week open-label run-in (−10.6%), then randomized: continue sema vs switch to placebo × 48 weeks.
  • Week 20→68: continued sema −7.9% more; placebo +6.9% regain (treatment difference −14.8 pp). Total loss on continued therapy ≈ −17.4%.

STEP 5 (Garvey et al., Nature Medicine 2022) — 2-year durability

  • 304 adults, 104 weeks: −15.2% vs −2.6%; ≥5%: 77.1% vs 34.4%; ≥10%: 61.8%; ≥15%: 52.1%; ≥20%: 36.1%.

STEP 6 (Kadowaki et al., 2022) — Asian T2D

  • SC 2.4 mg: −13.1% vs −2.3% placebo at 68 weeks (oral semaglutide 50 mg arm: −9.6%).

STEP 8 (2022) — head-to-head vs semaglutide 1 mg

  • 2.4 mg + behavioral program: −15.8% vs −10.5% (1 mg) at 72 weeks.

STEP 10 (Weghuber et al., NEJM 2022) — adolescents

  • −16.1% vs +0.6% at 68 weeks.

STEP-HFpEF (Kosiborod et al., NEJM 2023) + STEP-HFpEF DM (2024)

  • HFpEF + obesity, no diabetes: −13.3% vs −2.6% at 52 weeks; Kansas City Cardiomyopathy Questionnaire (KCCM-CSS) +7.8 points vs +1.6 placebo — a symptom/function improvement independent of weight loss.
  • STEP-HFpEF DM (with T2D): −9.8% vs −3.4%; KCCM-CSS +7.3.

SELECT (Lincoff et al., NEJM 2023) — cardiovascular outcomes

  • 17,604 adults ≥45 y, BMI ≥27, established CVD, no diabetes; sema 2.4 mg vs placebo; median follow-up ~40 months (mean exposure 33 months); 72% male.
  • Primary MACE (CV death, non-fatal MI, non-fatal stroke): 6.5% vs 8.0% — HR 0.80 (95% CI 0.72–0.90), 20% relative risk reduction, p<0.001. Directionally consistent across components.
  • Weight: −9.4% at 104 weeks; waist −7.4 cm.
  • Discontinuation: 16.6% vs 8.2% (mostly GI). Subsequent analyses show the CV benefit is largely independent of the amount of weight lost (Lancet 2025 prespecified analysis).

Semaglutide side-effect highlights (STEP 1 rates)

| AE | Semaglutide 2.4 mg | Placebo | |---|---|---| | Nausea | 44.2% | 14.9% | | Diarrhea | 29.9% | 16.3% | | Vomiting | 24.8% | 7.7% | | Constipation | 24.8% | 14.0% | | Discontinuation for AE | 7.0% | 3.1% | | Cholelithiasis | ~1.6% | ~0.7% | | Heart rate | +1–4 bpm | ~0 |

3.3 Official titration — semaglutide (Wegovy label)

| Weeks | Weekly dose | Notes | |---|---|---| | 1–4 | 0.25 mg | Starting dose (tolerability only) | | 5–8 | 0.5 mg | | | 9–12 | 1.0 mg | | | 13–16 | 1.7 mg | | | 17+ | 2.4 mg | Maintenance maximum | | Ozempic (T2D) | 0.25 → 0.5 → 1.0 mg | 1.0 mg max for T2D (2.0 mg approved in some markets) |

All steps are 4 weeks apart. The 0.25 mg starting dose is ~10% of the therapeutic dose — this is the classic "why am I not losing weight in month one?" confusion.

4. Retatrutide — Deep Dive

4.1 Pharmacology

  • Identity. Retatrutide (LY3437943) is a single ~39-amino-acid peptide conjugated to a fatty diacid moiety. It agonizes GIP, GLP-1 and glucagon (GCG) receptors — the first-in-class "triple agonist" (Lilly).
  • Receptor potency balance (from NEJM phase 2 paper): vs native ligands, retatrutide is 8.9-fold more potent at the human GIP receptor, but 0.3-fold at the GCG receptor and 0.4-fold at the GLP-1 receptor. Reference EC50s (review literature): GLP-1R ≈0.775 nM, GCGR ≈5.79 nM (i.e., GIP > GLP-1 >> GCG in absolute potency).
  • Why the glucagon arm matters. GCG agonism increases energy expenditure (thermogenesis, fat oxidation, lipolysis), suppresses lipogenesis, and drives liver fat mobilization — the mechanism behind retatrutide's superior fat loss and ~20% LDL reduction. The hyperglycemic tendency of glucagon is blunted by the GLP-1/GIP arms (insulin secretion, glucagon suppression).
  • PK. Dose-proportional; half-life ≈6 days; once-weekly SC; steady state ~4–5 weeks.
  • Status. Investigational only. Phase 2 (NEJM 2023), then the TRIUMPH phase-3 program (5+ positive trials by mid-2026). BLA submission to FDA planned Q1 2027 (Lilly, July 2026); earliest realistic US launch late 2027/2028; EU later. No Fast Track / Breakthrough designation publicly announced as of Feb 2026. This molecule is therefore available ONLY as research-grade peptide — the single highest-demand, highest-risk SKU in the GLP-1 gray market (§8, §10).

4.2 Clinical trial data with numbers

Phase 2 (Jastreboff et al., NEJM 2023; NCT04881760) — the landmark

  • 338 adults with obesity (no diabetes), 48 weeks; doses 1 / 4 / 8 / 12 mg (some arms started at 2 mg vs 4 mg to test escalation tolerability) vs placebo.
  • Week 24 (primary): up to −17.5% (12 mg).
  • Week 48 (secondary): −8.7% (1 mg); −16.3% (4 mg, 2 mg start) / −17.8% (4 mg, 4 mg start); −21.7% (8 mg, 2 mg start) / −23.9% (8 mg, 4 mg start); −24.2% (12 mg) vs −2.1% placebo. No plateau reached at week 48 — the weight curves were still descending.
  • ≥5% / ≥10% / ≥15% at 48 weeks (12 mg): 100% / 93% / 83%; (8 mg): 100% / 91% / 75%; (4 mg): 92% / 75% / 60%.
  • 2 mg vs 4 mg starting dose: the 2 mg start produced markedly fewer GI events with equal efficacy → phase 3 adopted universal 2 mg start.
  • Safety: GI events dose-dependent — nausea up to ~58–60% (12 mg), vomiting up to ~25–39%, diarrhea up to ~23–43%; discontinuation for AE 16–17% at higher doses; resting HR +6.7–6.9 bpm (peak ~week 24, then declining toward baseline by weeks 36–48); LDL ≈ −20%; transient ALT elevations in a subset.

TRIUMPH-1 (Lilly topline, May 21, 2026; ADA 2026) — pivotal obesity

  • 2,339 adults (obesity/overweight + ≥1 comorbidity, no diabetes), 80 weeks; 4 / 9 / 12 mg (all started 2 mg, +step every 4 weeks) vs placebo.
  • −19.0% (4 mg), −25.9% (9 mg), −28.3% (12 mg) vs −2.2% placebo (efficacy estimand: −19% / −25.9% / −28.3%; baseline mean 112.6 kg / BMI 40.0).
  • 45.3% of 12 mg arm lost ≥30% (bariatric-surgery territory); ~1 in 4 lost ≥35%.
  • 65.3% of 12 mg arm reached BMI <30 (including 37.5% of those starting at BMI ≥40).
  • No weight-loss plateau observed.
  • Extension (blinded, pre-specified, baseline BMI ≥35, 12 mg): −30.3% (85 lb) at 104 weeks.
  • Sleep-apnea substudy: AHI reduced 60.6% from severe baseline (first strong non-weight signal).

TRIUMPH-4 (Dec 11, 2025; knee osteoarthritis) — first successful phase 3

  • Obesity + knee OA: 12 mg → −28.7% at 68 weeks + substantial OA pain relief (function/WOMAC improvements).

TRIUMPH-2 & TRIUMPH-3 (topline July 23, 2026)

  • TRIUMPH-2 (obesity + T2D): up to −20.8% at 80 weeks (12 mg).
  • TRIUMPH-3 (severe obesity + established CVD): up to −22.6% at 80 weeks (12 mg).
  • Together with TRIUMPH-1/4 and TRANSCEND-T2D-1: five positive phase-3 trials → Lilly committed to global submissions (obesity, knee OA pain, OSA).

TRANSCEND-T2D-1 (March 2026)

  • T2D + obesity: 12 mg → −16.8% weight, −2.0% A1c at 40 weeks.

TRIUMPH-4 safety table (12 mg, per Noom/secondary sources)

| AE | Reta 12 mg | Placebo | |---|---|---| | Nausea | 43.2% | 10.7% | | Diarrhea | 33.1% | 13.4% | | Constipation | 25.0% | 8.7% | | Vomiting | 20.9% | ~0 | | Dysesthesia (skin sensation) | 20.9% | 0–0.7% | | Discontinuation for AE | 12–18% (program range) | low |

4.3 Official/trial titration — retatrutide

| Weeks | Weekly dose (trials) | Community norm (§7) | |---|---|---| | 1–4 | 2 mg | 0.5–2 mg (start conservative) | | 5–8 | 4 mg | 1–4 mg | | 9–12 | 6 mg (some phase-3 arms step 4→9) | 2–4 mg ("sweet spot") | | 13–16 | 9 mg | 3–6 mg | | 17–20 | 12 mg | 4–8 mg (aggressive) | | Maintenance | 4 / 9 / 12 mg (trial maintenance doses) | taper to lowest effective; many stay 2–4 mg |

Key tolerability finding: starting at 2 mg (not 4 mg) cuts GI events substantially; the phase-3 program therefore started everyone at 2 mg. Community users who ignore this and start at 4+ mg report miserable week 1–2 nausea.

5. Vial-Based Practical Protocols

RUO reminder. Everything below is the standard research practice for handling lyophilized peptide vials. Reconstitution, storage and dosing math are the same regardless of end use, but these products are labeled for laboratory use only.

5.1 Why GLP-1s come as lyophilized powder in 20–30 mg vials

  1. Lyophilization (freeze-drying) is the only stable format. These peptides degrade in solution; the dry powder keeps ≥95% potency for 12–24 months at −20 °C. Multi-dose pens are a pharma convenience; research-grade supply is powder.
  2. Multi-month dosing economics. A 30 mg tirzepatide vial = 12 weeks at 2.5 mg or 6 weeks at 5 mg — a full titration cycle from one vial, at a fraction of branded-pen cost per mg.
  3. Flexible titration. Pens are fixed-dose; vials let researchers/consumers micro-dose, split-dose, taper and stack (see §7). This flexibility is the core reason the gray market standardized on 10/20/30/60 mg formats.
  4. Overfill. Vendors typically fill ~5–10% over label (e.g., a "30 mg" vial often assays 31–33 mg) to cover loss on reconstitution — good vendors publish Janoshik mg/vial numbers confirming this.

5.2 Reconstitution — the non-negotiables

  • Diluent. Bacteriostatic water (BAC water): sterile water with 0.9% benzyl alcohol. The benzyl alcohol preserves the reconstituted solution for multi-week refrigerated use. Plain sterile water / saline = no preservative = 24–72 h viability, discard after. Never use sodium chloride for injection with benzyl alcohol if cloudy.
  • Volume choice. Add enough BAC so your target dose lands on an easy syringe marking. There is no "correct" volume — the peptide doesn't care; your syringe does.
  • Technique.
    1. Wipe both vial stoppers with 70% alcohol; let dry.
    2. Draw BAC into a fresh syringe (use the supplied/sterile 3 mL syringe for large volumes).
    3. Inject the BAC slowly down the inside wall of the peptide vial — never straight onto the powder cake (foaming/denaturation risk).
    4. Roll/swirl gently to dissolve. NEVER shake — shaking denatures the peptide and creates aggregates (see Janoshik aggregate testing, §9).
    5. Let it sit 5–10 min; solution should be clear and colorless. Cloudy/particulate = discard.
    6. Label vial with peptide, concentration (mg/mL), reconstitution date.
  • Storage. Reconstituted: refrigerated 2–8 °C; use within ~30 days (benzyl alcohol keeps it safe longer, but peptide potency and aggregate formation favor the 30-day window). Never freeze reconstituted solution. Powder: −20 °C, desiccated, light-protected.

5.3 The universal unit math (memorize this)

  • U-100 insulin syringe: 100 units = 1.0 mL. 1 unit = 0.01 mL.
  • Concentration (mg/mL) = vial mg ÷ BAC mL.
  • mcg per unit = (vial mg × 1000) ÷ BAC mL ÷ 100.
  • Dose in units = dose (mcg) ÷ mcg-per-unit.
  • 1 mg = 1,000 mcg. The community speaks in mcg: 2.5 mg = 2,500 mcg; 0.25 mg = 250 mcg.

Quick reference: 10 mg/mL concentration (the community standard) = 100 mcg per unit. Then: 2.5 mg = 25 u, 5 mg = 50 u, 10 mg = 100 u, 2 mg = 20 u, 0.5 mg = 5 u, 0.25 mg = 2.5 u.

5.4 Protocol A — 30 mg Tirzepatide vial

Reconstitute with 3 mL BAC → 10 mg/mL → 100 mcg/unit.

| Phase | Weekly dose | Units (U-100) | mL | Vial lasts | |---|---|---|---|---| | Weeks 1–4 (start) | 2.5 mg (2,500 mcg) | 25 u | 0.25 mL | 12 weeks | | Weeks 5–8 | 5.0 mg | 50 u | 0.50 mL | 6 weeks | | Weeks 9–12 | 7.5 mg | 75 u | 0.75 mL | 4 weeks | | Weeks 13–16 | 10 mg | 100 u | 1.00 mL | 3 weeks | | Weeks 17–20 | 12.5 mg | 125 u | 1.25 mL | 2.4 weeks | | Maintenance | 15 mg | 150 u | 1.50 mL | 2 weeks | | Low-dose/micro | 1.25–2.5 mg | 12.5–25 u | 0.125–0.25 mL | 12–24 weeks | | Split dose | 2.5 mg ×2/wk (e.g., Mon+Thu) | 25 u per shot | 0.25 mL | 6 weeks |

Alternative (preferred by some): reconstitute with 2 mL BAC → 15 mg/mL → 150 mcg/unit → 2.5 mg = 16.7 u (awkward), 5 mg = 33.3 u, 7.5 mg = 50 u. The 3 mL/10 mg/mL standard keeps every label dose on clean markings — use it.

5.5 Protocol B — 20 mg Semaglutide vial

Reconstitute with 4 mL BAC → 5 mg/mL → 50 mcg/unit. (Do NOT use 2 mL → 10 mg/mL → 0.25 mg = 2.5 units — too small to draw accurately; semaglutide needs the more dilute 5 mg/mL convention.)

| Phase | Weekly dose | Units (U-100) | mL | Vial lasts | |---|---|---|---|---| | Weeks 1–4 (start) | 0.25 mg (250 mcg) | 5 u | 0.05 mL | 80 weeks | | Weeks 5–8 | 0.5 mg | 10 u | 0.10 mL | 40 weeks | | Weeks 9–12 | 1.0 mg | 20 u | 0.20 mL | 20 weeks | | Weeks 13–16 | 1.7 mg | 34 u | 0.34 mL | 11.8 weeks | | Maintenance | 2.4 mg | 48 u | 0.48 mL | 8.3 weeks | | Ozempic-style (T2D cap) | 0.5–1.0 mg | 10–20 u | 0.10–0.20 mL | 20–40 weeks | | Low-dose | 0.25–0.5 mg | 5–10 u | 0.05–0.10 mL | 40–80 weeks |

Note: 0.25 mg = 5 units is the minimum practical draw on a 100-unit syringe. Users wanting more headroom often reconstitute 20 mg with 8 mL BAC (2.5 mg/mL → 25 mcg/u → 0.25 mg = 10 u), at the cost of 8 injections' worth of volume in the vial (fridge space) — acceptable.

5.6 Protocol C — 30 mg Retatrutide vial

Reconstitute with 3 mL BAC → 10 mg/mL → 100 mcg/unit.

| Phase | Weekly dose | Units (U-100) | mL | Vial lasts | |---|---|---|---|---| | Weeks 1–4 (start) | 2 mg (2,000 mcg) | 20 u | 0.20 mL | 15 weeks | | Community conservative | 0.5–1 mg | 5–10 u | 0.05–0.10 mL | 30–60 weeks | | Weeks 5–8 | 4 mg | 40 u | 0.40 mL | 7.5 weeks | | Weeks 9–12 | 6 mg | 60 u | 0.60 mL | 5 weeks | | Weeks 13–16 | 8–9 mg | 80–90 u | 0.80–0.90 mL | 3.3–3.75 weeks | | Maintenance (trial) | 9–12 mg | 90–120 u | 0.90–1.20 mL | 2.5–3.3 weeks | | Sweet spot (community) | 2–4 mg | 20–40 u | 0.20–0.40 mL | 7.5–15 weeks |

Split dosing for retatrutide is common (e.g., 2 mg every 3.5–4 days ≈ 4 mg/week equivalent) because the 6-day half-life and strong GCG-driven sides make some users prefer smaller, more frequent shots. Trial data support only once-weekly dosing; split dosing is community practice only.

5.7 Vial longevity table (all protocols, standard concentrations)

| Vial | Concentration | Dose | Weeks per vial | |---|---|---|---| | 30 mg Tirz (3 mL) | 10 mg/mL | 2.5 mg | 12 | | 30 mg Tirz (3 mL) | 10 mg/mL | 5 mg | 6 | | 30 mg Tirz (3 mL) | 10 mg/mL | 10 mg | 3 | | 20 mg Sema (4 mL) | 5 mg/mL | 0.5 mg | 40 | | 20 mg Sema (4 mL) | 5 mg/mL | 1.0 mg | 20 | | 20 mg Sema (4 mL) | 5 mg/mL | 2.4 mg | 8.3 | | 30 mg Reta (3 mL) | 10 mg/mL | 2 mg | 15 | | 30 mg Reta (3 mL) | 10 mg/mL | 4 mg | 7.5 | | 30 mg Reta (3 mL) | 10 mg/mL | 12 mg | 2.5 |

6. Side Effects, Management & Contraindications

6.1 Class-wide side-effect profile (incidence ranges across trials)

| System | Effect | Tirz (15 mg) | Sema (2.4 mg) | Reta (12 mg) | |---|---|---|---|---| | GI | Nausea | 24.6–29% | 44.2% | 43–60% | | GI | Diarrhea | 21.7% | 29.9% | 33–43% | | GI | Constipation | 18.7% | 24.8% | 18–25% | | GI | Vomiting | 8.9% | 24.8% | 21–39% | | GI | Abdominal pain/discomfort | 7–10% | ~10% | common | | Cardiovascular | Resting HR increase | +2–4 bpm | +1–4 bpm | +6.7–6.9 bpm (transient peak ~wk 24) | | Hepatobiliary | Gallstones/cholecystitis | 1.6%/0.6% | ~1.6% | reported, program-wide low | | Skin | Dysesthesia (paresthesia) | rare | rare | 4.4–20.9% (dose-dependent) | | Metabolic | Hypoglycemia | rare (unless sulfonylurea/insulin) | rare | rare | | Other | Injection-site reactions | common, mild | common, mild | common, mild | | Other | Fatigue, headache, hair loss (telogen effluvium) | reported | reported | reported |

GI events cluster in the escalation phase. The first 2–4 weeks after each dose bump are the worst; most users habituate. This is the single most important counseling point for any buyer.

6.2 Management playbook (non-medical, informational)

  1. Titrate, don't accelerate. Stay at each dose 4 weeks. If week 1 nausea is severe, stay at the starting dose an extra 2–4 weeks. Never "double up" after a missed dose.
  2. Eat small, frequent, low-fat meals. Fatty meals amplify nausea/vomiting. Protein-forward meals protect muscle (see 6.5).
  3. Hydration + electrolytes. GI losses and reduced intake cause dehydration; this is the most common cause of "flu-like" reports.
  4. OTC aids. Ginger, small carbonated water sips, and for constipation osmotic laxatives / fiber. Antiemetics (e.g., ondansetron) are prescription-only — advise users to consult a clinician; do not recommend prescription drugs as a vendor.
  5. Dose-skip rule (from trial protocols). If GI symptoms are intolerable, skip one weekly dose (do not halve mid-week), resume at the same or one step lower.
  6. Split dosing (tirz 2×/wk, reta 2×/wk, sema 1×/wk is standard but split-able) smooths the Cmax and reduces peak nausea — community-tested, not label.
  7. Injection-site rotation (abdomen, thigh, upper arm) reduces lipohypertrophy and site reactions.
  8. Alcohol. Reduced intake is common (GLP-1s blunt alcohol reward — a documented effect); users should keep alcohol minimal to avoid hypoglycemia on empty stomachs.

6.3 Muscle loss — the #1 informed-buyer concern

  • The data. STEP 1 DXA: ~40% of weight lost was lean soft tissue (6.9 kg LST vs 10.4 kg FM). SURMOUNT-1 DXA: ~26% lean (5.6 kg LST vs 15.9 kg FM) — the GIP arm appears to protect lean mass better. Retatrutide's glucagon arm increases fat oxidation further; DXA data from TRIUMPH program pending, community DEXA logs suggest reta lean fraction roughly comparable to tirz.
  • Range across literature: lean mass ≈ 25–45% of total loss on semaglutide, 25–35% on tirzepatide; highly individual. Recent real-world EHR/BIA analyses (2026) suggest greater LBM decline with tirzepatide than semaglutide in routine care, an open controversy.
  • Mitigation (what every user should be told):
    • Resistance training 2–3×/week (trial-adjacent evidence shows it preserves LBM).
    • Protein ≥1.2–2.0 g/kg/day (community standard; higher end during active loss).
    • DEXA before and every 3 months if available.
    • Slower titration to keep loss at 0.5–1%/week — rapid loss = higher lean fraction.
  • Counterpoint from the literature: muscle volume loss is largely proportional to the weight lost (expected adaptation), and both tirzepatide and semaglutide reduce muscle fat infiltration — i.e., muscle quality improves even as volume drops (Circulation 2024 state-of- the-art review; Dom 2024).

6.4 Rebound / discontinuation — set expectations honestly

  • SURMOUNT-4: stopping tirz → +14% regain in 52 weeks (vs continued −5.5%).
  • STEP 4: stopping sema → +6.9% regain in 48 weeks.
  • SELECT: ~⅔ of weight lost was regained within 1 year of stopping.
  • Implication for buyers: GLP-1s are chronic-use molecules. The gray-market model is repeat-purchase: vials, then maintenance vials, then taper vials. Any vendor content that implies "a course and done" is misleading and increases refund/complaint risk.
  • Community taper practice: reduce dose 25–50% every 2–4 weeks to a low maintenance dose (tirz 2.5–5 mg; sema 0.25–0.5 mg; reta 1–2 mg) rather than stopping cold.

6.5 Serious AEs & contraindications (class labeling)

Serious but rare:

  • Pancreatitis (acute; ~0.1–0.2% in trials). Stop drug; suspect if severe abdominal pain radiating to back.
  • Gallbladder disease (cholelithiasis 1.2–2.2%, cholecystitis ~0.6% across trials) — driven by rapid weight loss; counsel about right-upper-quadrant pain.
  • Medullary thyroid carcinoma (MTC) / C-cell tumors — rodent findings (all GLP-1RAs); boxed warning on label; absolute contraindication: personal/family history of MTC or MEN-2.
  • Diabetic retinopathy — caution in T2D patients with proliferative retinopathy (SUSTAIN-6 signal; mechanism likely rapid glycemic improvement).
  • Gastroparesis / delayed emptying — a real effect; caution in people with severe gastroparesis, and in the peri-procedural setting (aspiration risk under anesthesia — buyers using before surgery should pause per label guidance; label says hold before elective surgery with general anesthesia).
  • Suicidality — investigated by EMA PRAC and FDA; no causal link found (EMA PRAC April 2024: "available evidence does not support a causal association"; FDA preliminary evaluation January 2024: no evidence). Monitor standard psychiatric risk factors regardless.
  • Hypoglycemia — only clinically relevant when combined with insulin or sulfonylureas.
  • HR increase — retatrutide's +7 bpm is dose-dependent and transient; caution in tachyarrhythmia-prone users; dedicated CVOT data still pending.
  • Hepatobiliary/liver — transient ALT elevations (reta); no hepatotoxicity signal in trials.

Contraindications (label):

  1. Personal or family history of MTC / MEN-2.
  2. Known hypersensitivity to the peptide or excipients.
  3. Pregnancy (discontinue ≥2 months before planned conception — long half-life washout) and breastfeeding.
  4. Severe GI disease, gastroparesis (caution), inflammatory bowel disease (caution).
  5. History of pancreatitis (caution, not absolute).

7. Community / Gray-Market Practice

What follows is ethnographic documentation of how the research-peptide underground actually operates (r/Peptides, r/Tirzepatide, r/Semaglutide, r/Retatrutide, r/RetatrutideGBP, MesoRx, vendor guides). It is included so VALEN LABS sales/support can speak the community's language — not as endorsement of human use.

7.1 Why the community exists

Branded GLP-1s are expensive (US$935–1,350/month list), prescription-gated, and — through 2023–2024 — shortage-ridden. Compounded versions filled the gap until FDA shut the shortage door (§8.2), pushing demand further into research-grade peptide vials from China/EU/US resellers at US$1–4/mg. The community is enormous: r/Tirzepatide alone has hundreds of thousands of members; "gray" (gray-market) is the standard in-group term.

7.2 Dosing language — mcg/week equivalents

The community doses in mcg, not mg:

| Molecule | Label dose | Community "mcg" | |---|---|---| | Tirzepatide | 2.5 mg | 2,500 mcg | | Tirzepatide | 5 mg | 5,000 mcg | | Tirzepatide | 10 mg | 10,000 mcg | | Semaglutide | 0.25 mg | 250 mcg | | Semaglutide | 1.0 mg | 1,000 mcg | | Semaglutide | 2.4 mg | 2,400 mcg | | Retatrutide | 2 mg | 2,000 mcg | | Retatrutide | 4 mg | 4,000 mcg | | Retatrutide | 12 mg | 12,000 mcg |

When a community member says "I'm on 2500 mcg of Tirz," they mean the 2.5 mg weekly dose.

7.3 The 20–30 mg vial convention (compounding conversions)

  • Why 30 mg for tirz/reta and 20 mg for sema: one vial ≈ one full titration cycle; easy math at 10 mg/mL (30 mg + 3 mL) or 5 mg/mL (20 mg + 4 mL); per-mg price collapses with vial size (a 30 mg vial often costs less per mg than a 10 mg vial).
  • Compounding conversions: compounding pharmacies historically prepared "patient-specific" multi-dose vials at 5–10 mg/mL concentrations from bulk API — the exact same math the community uses. 503A/503B crackdowns (§8.2) moved this demand to research channels; the vial formats (10/15/20/30/60 mg) were inherited from compounder supply chains.
  • Overfill culture: reputable gray vendors pay for Janoshik testing and advertise measured mg/vial (e.g., "30 mg vial assays 31.4 mg, 99.6% purity") — this is the trust currency of the market (§9).

7.4 Community dosing norms by molecule (consensus from user logs)

Tirzepatide

  • Start 2.5 mg weekly ×4 wk (some ultra-conservative: 1.25–2.5 mg "micro" start).
  • Escalate 2.5 mg steps every 4 weeks; most never exceed 10 mg.
  • "Working dose" usually 5–7.5 mg; maintenance 2.5–5 mg weekly or 5 mg q10–14d.
  • Split dosing (half ×2/week) for side-effect control is widespread.
  • Stacking: Tirz+Reta is the most common gray-market "double stack."

Semaglutide

  • Start 0.25 mg weekly ×4 wk; many stop at 0.5–1.0 mg (sema is the most side-effect-prone per unit of efficacy).
  • Max community dose mirrors Wegovy: 2.4 mg; some push 3.0–4.0 mg (evidence-free; more sides).
  • Frequently stacked with cagrilintide ("CagriSema-style" stacks) in the gray market.
  • Sema caution: 5 mg vials are the norm; a 20 mg vial lasts months — ensure users understand fridge life of reconstituted product (30 days practical) before buying 20 mg.

Retatrutide

  • Community doses far below trials. Trials pushed 4/9/12 mg; the gray crowd lives at 2–4 mg/week, starting at 0.5–1 mg and titrating +0.5–1 mg every 2–4 weeks "by feel."
  • Rationale: reta's glucagon arm makes sides (nausea, HR, dysesthesia) hit harder per mg; user logs show nausea "climbs hard above 4 mg."
  • Sweet spot commonly reported: 2–4 mg/week; aggressive: 6–8 mg.
  • Half-life ~6 days → some dose q5–6 days or split 2×/week.
  • Long-term: taper to 1–2 mg maintenance rather than stop cold (rebound).
  • Reta+Tirz stack is the current gray-market meta (both Lilly molecules; users report smoother appetite control), though drug-interaction data do not exist.

7.5 Stacking landscape (informational)

| Stack | Typical doses (community) | Evidence | |---|---|---| | CagriSema-style (cagrilintide + sema) | cagri 0.3–0.6 mg + sema 0.5–1.0 mg | Novo's phase-3 CagriSema: −22.7% at 68 wk (2.4+2.4 mg, REDEFINE-1); −15.7% in T2D (REDEFINE-2) — but fixed pen; gray stacks are unstudied | | Tirz + Reta | tirz 2.5–5 + reta 1–2 mg | No data; popularity from combined anorectic + thermogenic effect | | GLP-1 + tesofensine | — | No data; dopamine reuptake inhibitor adds sides | | GLP-1 + GH secretagogues (Ipamorelin/CJC) | — | Unstudied; theoretical muscle-preservation angle | | GLP-1 + AOD-9604 | — | Unstudied; popular "fat-burner" pairing |

Vendor policy recommendation: never recommend stacking; mention it only as observed community practice with an explicit "no interaction data exist" caveat.

7.6 Community red flags a vendor should pre-empt

  • "It's just water weight, you'll be fine" dismissals — no, users get real nausea.
  • Buying a 60 mg reta vial for a first cycle — guarantee of misery; push 10/30 mg.
  • Reconstituting with 1 mL for a 30 mg vial "to save volume" — 30 mg/mL concentration is hyper-concentrated, painful, and hard to dose (2 mg = 6.7 u).
  • Using plain sterile water for a multi-week vial — contamination risk.
  • Expecting results in week 1 — manage expectations with the 4-week ramp reality.

8. Risk & Compliance (US · EU · Serbia · RUO)

8.1 Regulatory status summary (mid-2026)

| Molecule | US | EU | Serbia (ALIMS) | Gray-market status | |---|---|---|---|---| | Semaglutide | Approved (Ozempic/Wegovy). Compounding of "essentially a copy" restricted | Approved (Ozempic/Wegovy) | Approved (Ozempic; Wegovy entering) | High volume; RUO-labeled vials | | Tirzepatide | Approved (Mounjaro/Zepbound). Compounding restricted | Approved (Mounjaro; weight mgmt 2023–24) | Approved/rolling (Mounjaro registered; availability limited) | Very high volume | | Retatrutide | Not approved. FDA warning letters vs sellers (Sept 2025) | Not approved. EMA no opinion | Not approved | Explosive demand; highest enforcement attention |

8.2 US compounding saga (why the gray market boomed)

  • 2022: semaglutide (Ozempic/Wegovy) placed on FDA Drug Shortage List; tirzepatide (Mounjaro) added Dec 2022; Zepbound added 2024. Shortage status let 503A pharmacies and 503B outsourcing facilities compound "essentially a copy" at scale → the compounding boom (2023–2024): telehealth clinics + compounders sold cheap sema/tirz vials to millions.
  • Oct 2, 2024: FDA removes tirzepatide from the shortage list → Outsourcing Facilities Association v. FDA (E.D. Tex.) → court-ordered re-evaluation; FDA re-adds tirzepatide (April 2025) under the injunction.
  • Feb 21, 2025: FDA removes semaglutide from the shortage list; 60-day (503A, to Apr 22) and 90-day (503B, to May 22) grace periods to wind down compounding of copies. OFA files a parallel suit.
  • Late 2025 / 2026: FDA again determines the tirzepatide shortage resolved ("determines again"), with grace periods; litigation ongoing; as of May 2026 both molecules are officially "resolved" — compounding reverts to narrow, non-shortage bases (individualized 503A, or products with a clinical difference like alternate dosing forms/strengths where legally defensible).
  • Enforcement wave:
    • Sept 9, 2025: FDA warning letters to websites selling compounded retatrutide and other GLP-1s as unapproved new drugs / misbranded.
    • Late 2025: 40+ warning letters to telehealth compounders for advertising equivalence claims.
    • June 16, 2026: 25 more warning letters to telehealth companies for false/misleading claims about compounded semaglutide, tirzepatide (and one liraglutide).
    • State AG action: Connecticut AG sued a GLP-1 distributor ("Triggered Brand") over bootleg GLP-1 sales.
    • Poison centers: retatrutide-related exposures +265% in early 2026 (Allegheny County Health Dept / FDA messaging).
  • Net effect: branded prices are the ceiling, compounding is squeezed, and the unregulated peptide-vial market absorbs the overflow — with the FDA publicly telling consumers that "research-use-only" GLP-1 products are unapproved drugs when intended for human use.

8.3 EU & Serbia specifics

  • EU: Mounjaro (tirz) approved for T2D (Dec 2022) and weight management (2023–24); Wegovy (2022). EU has no meaningful compounding loophole for these products — pharmacy compounding of GLP-1s is not a recognized channel. Supply is prescription-only, price-controlled in many member states, and frequently shortage-constrained → cross-border gray purchases and research-grade vials fill gaps. EMA PRAC (April 2024) closed the suicidality question (no causal link). EMA repeatedly warns about falsified Ozempic pens circulating in the EU/EEA supply chain (WHO also issued global alerts for fake Ozempic batches, incl. batches found in Europe).
  • Serbia (ALIMS): Ozempic is registered and dispensed (with documented counterfeit warnings echoed by the Serbian Intellectual Property Office and WHO alerts); Wegovy/Mounjaro availability has been limited/rolling; demand is high and prices are materially above EU reference prices at times → significant parallel/gray import behavior. ALIMS (Agencija za lekove i medicinska sredstva Srbije) regulates medicines; research peptides are sold as lab reagents/laboratory supplies (RUO) — the same framing as the rest of the EU.
  • RUO framing is the operative legal shield in EU/Serbia/US: "For research use only. Not for human or veterinary use." This keeps the product out of the medicines regulatory scope only as long as (a) no therapeutic claims are made, (b) no dosing-for-humans guidance is shipped, (c) marketing language stays in the lab/research register, and (d) customs declarations are honest ("lyophilized peptide for laboratory research"). The moment a vendor writes "how to dose this for weight loss," they cross into unapproved-drug territory in every jurisdiction listed.

8.4 Why RUO matters (and where the line is)

  1. It is a labeling/positioning device, not a magic shield. FDA has explicitly said products labeled "research use only" that are intended for human use are unapproved new drugs; intent is inferred from marketing, social media, dosing guides, and customer service language.
  2. Platform risk: Reddit banned sourcing discussions (r/Peptides removed vendor sourcing; r/Tirzepatide, r/Retatrutide heavily moderated); Etsy/Amazon/Shopify remove GLP-1 listings; payment processors (Stripe/PayPal) freeze peptide merchants; Facebook/Instagram ads are banned for GLP-1 claims. RUO framing is what keeps a store alive on these rails.
  3. Customs risk: EU/Serbia customs seize peptide shipments; RUO lab-supply declarations with truthful product names and third-party COAs improve (not guarantee) clearance.
  4. Crackdown trajectory (2025–2026) is toward the whole unregulated channel, not just bad actors: warning letters, import alerts, poison-center data campaigns, state AG suits. Any VALEN LABS content must keep the research frame airtight (§12 compliance language).

9. Testing — Janoshik GLP-1 Blind Panel & How to Read a COA

9.1 Why third-party testing is the market's trust currency

Gray-market peptides are unregulated; the single biggest buyer fear is wrong peptide, short fill, or dirty batch. The community's answer is independent analytical testing with publicly verifiable certificates. Janoshik Analytical (janoshik.com) is the de-facto standard lab for peptide COAs in this market; competitors include MZ Biolabs (now part of Janoshik's ecosystem), Cayman-referenced HPLC services, and Gold Standard Analytics. Janoshik's COA verification portal (janoshik.com/verify) lets anyone check a batch result by key — vendors that publish verifiable Janoshik COAs command premium pricing.

9.2 The Janoshik GLP-1 blind test — exact panel

Product: "Common GLP-1 peptide blind test (Semaglutide, Tirzepatide and Retatrutide)" Price: US$360 base (as listed; CZK 7,574). Blind = the client does not have to tell the lab which of the three peptides is in the vial.

What it reports:

  1. Identity (ID) — which peptide(s) is/are actually present. In a blind test the lab identifies the molecule from the analytical data (retention time + mass). If the vial contains a mixture of the three, ID and amount of ALL will be reported — this is the anti-counterfeit guarantee (catches vials labeled "Reta" that actually contain semaglutide or nothing).
  2. Amount (mg per vial) — quantitative fill vs label claim (e.g., "30 mg vial → 31.4 mg"). Detection limit: less than 1/20th of the usual dosage per vial.
  3. Peptide purity (%) — HPLC main-peak purity (typical results: 99.3–99.9% for good vendors). Results given as mg/vial for lyophilizates (or m/m purity for raw API powder if the alternative format is selected).

Method: HPLC (with mass-spectrometry confirmation for identity where applicable). Typical COA includes the chromatogram, calculated mass, purity, and mg/vial.

Target compounds & reference data published on the panel: | Peptide | CAS | Molecular weight (Janoshik) | Notes | |---|---|---|---| | Semaglutide | 910463-68-2 | 4113.6 Da | 31-aa acylated GLP-1 analogue | | Tirzepatide | 2023788-19-2 | 4813.5 Da | 39-aa dual agonist, C20 diacid | | Retatrutide | 2381089-83-2 | 4731.3 Da | 39-aa triple agonist (some references list ~4756 Da; salt/counterion differences account for variance — check the COA's stated theoretical mass) |

Add-on services (à la carte): | Add-on | Price | Purpose | |---|---|---| | GLP-1 aggregate analysis | +$150 | Oligomer/aggregate detection — cytotoxicity/immunogenicity risk (shaking, heat, bad storage) | | TFA analysis | +$290 | Trifluoroacetic acid (synthesis counterion) mg/vial — high TFA = tissue irritation risk | | Endotoxin analysis (LAL) | +$180 | LPS; accurate ≤10 EU/vial (re-test at $120 above 10 EU); finished products only; two vials recommended | | Sterility (TAMC/TYMC) | +$290 | Bacteria & mold; needs unopened extra vial; ~14-day turnaround | | CHNS mass report | +$145 | Elemental nitrogen/sulfur → gold-standard net peptide content (NPC) | | LCMS peptide-contamination screen | +$205 | Detects other peptides/degraded peptide contamination (ID only) | | Heavy metals (As, Cd, Pb, Hg) | +$105 | Toxic metal screen | | Fentanyl presence | +$75 | Safety screen | | pH measurement | +$35 | Formulation sanity check | | Variance testing | +$75 | Multiple vials same batch → intra-batch consistency | | Raw data | +$25 | Full instrument output | | Additional report (separate client name) | +$35 | Reseller branding of COAs |

Sample requirements: 1 whole unopened vial minimum for the lyophilizate panel; endotoxin and sterility need additional unopened vials.

9.3 What a good GLP-1 COA should contain (vendor-side checklist)

  1. Verifiable key — a public verification code/link (Janoshik verify portal). A PDF alone is forgeable; a portal entry is not.
  2. Blind ID result — "Identified as Retatrutide" etc. (means the lab didn't know the label).
  3. mg/vial amount — ideally ≥ label (overfill), never >5–10% under (short fill = vendor squeezing margin).
  4. Purity ≥99% — 99.3–99.9% is the good-batch band for these peptides; sub-98% = reject.
  5. Dimer/HMWP or aggregate result if ordered — high aggregates = bad synthesis/storage.
  6. Endotoxin <5 EU/dose-equivalent (pharma reference standard ≤5 EU/kg/hr; research buyers often accept <10 EU/vial) — important because these are injectable-route products.
  7. Batch number on vial and COA match — batch-level traceability.

9.4 Market reality on testing quality

  • Published market-surveillance data (JMIR study of unbranded online semaglutide, 2024): "99% purity" claims were frequently false — measured peptide content as low as 7.7–14.4% of label in some samples, with +28.6–38.7% overfill in others. This is why COA-verified vendors win.
  • Blind testing is specifically designed to catch mislabeled cross-contamination (e.g., a "Tirz" vial that's actually semaglutide) — the most common manufacturing failure in shared- reactor peptide synthesis.
  • Expect batch-to-batch variation; a single COA covers one batch only. Vendors should test every batch and publish the full history (Janoshik public results portal supports this).

10. Market Context — Why GLP-1 Is the Hottest and Riskiest SKU

10.1 The numbers

  • 2025 global GLP-1 sales ≈ US$130B+ (IQVIA/AMCP 2026 figures cited across industry media; some tallies ~US$132B, +33.5% vs 2024). By brand (2025): Mounjaro ≈ US$39.1B (+67%), Zepbound ≈ US$22.9B, Wegovy ≈ US$18.6B → tirzepatide alone >US$62B.
  • Projections: obesity medicines market US$66B (list, 2025) → US$92B (2026) → US$105–200B by 2027+ (IQVIA); GLP-1 class US$139B by 2030 (TD Cowen, 21% CAGR 2023–30); US$132.8B by 2035 (Towards Healthcare, more conservative base).
  • 190+ obesity products in development; the anti-obesity segment is the fastest-growing major pharma category — a 10× market growth in 4 years.
  • Patent cliff context: semaglutide composition patents begin expiring ~2026–2031 (US 2031; EU/India earlier; Indian generics already marketed post-March 2026 per industry reports) → future price compression at the branded level, but research-grade demand keeps rising because the molecules people actually want (Reta, Tirz) stay patent-protected and pen-expensive.

10.2 Why it's the hottest SKU for a research-peptide brand

  1. Massive, self-reinforcing demand — obesity is a lifelong condition; maintenance is indefinite; trials show regain on stop.
  2. Proven efficacy narrative — NEJM/Lancet headlines every quarter (SURMOUNT, TRIUMPH, SELECT) drive mainstream curiosity into research channels.
  3. Price arbitrage — US$1–4/mg gray vs US$25–30/mg branded-equivalent (list price per mg).
  4. Low per-unit manufacturing cost — solid-phase peptide synthesis is commodity-scale; 30 mg vials are cheap to produce.
  5. Repeats + stack culture — users buy titration kits → maintenance kits → stack vials (Reta+Tirz). LTV per customer is the highest in the peptide category.

10.3 Why it's simultaneously the riskiest

  1. Regulatory attention is unmatched — FDA warning-letter waves (Sept 2025, late 2025, June 2026), state AG suits, customs seizures, WHO/EMA counterfeit alerts, poison-center surveillance campaigns (Reta exposures +265% in early 2026).
  2. It's an approved drug class — unlike "novel research peptides," these molecules are recognized human medicines with brand owners (Lilly, Novo) who litigate aggressively (cease-and-desist letters to compounders; trademark enforcement).
  3. Platform/payments fragility — GLP-1 is the first peptide category to trigger systematic bans on Reddit, Etsy, Amazon, Shopify, Stripe/PayPal; merchants get deplatformed routinely.
  4. Safety optics — real AE burden (GI, HR, muscle loss, gallbladder); any media story ("woman hospitalized after buying GLP-1 online") is a category risk that regulators weaponize.
  5. Market surveillance published — peer-reviewed studies (JMIR 2024) document the gray market's bad-batch rate; regulators cite them.
  6. Retatrutide-specific: unapproved in every market; selling it with dosing advice is the clearest unapproved-new-drug exposure possible; expect pre-approval enforcement to intensify as the BLA (Q1 2027) approaches.

10.4 Positioning recommendation (internal)

  • Lead with education + verification: blind-tested COAs per batch, honest overfill data, RUO-only language, no human dosing claims on public pages.
  • Separate research documentation (this deep-dive style content, labeled "research reference") from any customer-facing dosing guidance.
  • Expect and prepare for platform enforcement: clean store copy, off-platform relationships, discreet packaging, honest customs declarations.
  • Watch Serbia/EU customs and ALIMS/MHRA-type actions; maintain RUO labeling in Serbian and English.

11. Sources

Primary trials (peer-reviewed)

  1. Jastreboff AM, et al. Tirzepatide Once Weekly for the Treatment of Obesity. NEJM 2022; 387:205–216 (SURMOUNT-1). doi:10.1056/NEJMoa2206038. NCT04184622. https://www.nejm.org/doi/full/10.1056/NEJMoa2206038
  2. Garvey WT, et al. Tirzepatide once weekly for the treatment of obesity in people with type 2 diabetes (SURMOUNT-2). Lancet 2023;402:613–626. https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(23)01200-X/abstract
  3. Wadden TA, et al. Tirzepatide after intensive lifestyle intervention (SURMOUNT-3). Nat Med 2023;29:2909–2918. https://www.nature.com/articles/s41591-023-02597-w
  4. Aronne LJ, et al. Continued Treatment With Tirzepatide for Maintenance of Weight Reduction (SURMOUNT-4). JAMA 2024;331:38–48. https://pubmed.ncbi.nlm.nih.gov/38078870/ and https://jamanetwork.com/journals/jama/fullarticle/2812936
  5. Wilding JPH, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1). NEJM 2021;384:989–1002. doi:10.1056/NEJMoa2032183. https://www.nejm.org/doi/full/10.1056/NEJMoa2032183
  6. Davies M, et al. Semaglutide 2·4 mg once a week in adults with overweight or obesity and type 2 diabetes (STEP 2). Lancet 2021;397:971–984.
  7. Wadden TA, et al. Effect of Subcutaneous Semaglutide vs Placebo as an Adjunct to Intensive Behavioral Therapy on Body Weight (STEP 3). JAMA 2021;325:1403–1413.
  8. Rubino D, et al. Effect of Continued Weekly Subcutaneous Semaglutide vs Placebo on Weight Loss Maintenance (STEP 4). JAMA 2021;325:1414–1425.
  9. Garvey WT, et al. Two-year effects of semaglutide in adults with overweight or obesity (STEP 5). Nat Med 2022;28:2083–2091. https://www.nature.com/articles/s41591-022-02026-4
  10. Lincoff AM, et al. Semaglutide and Cardiovascular Outcomes in Obesity without Diabetes (SELECT). NEJM 2023;389:2221–2232. doi:10.1056/NEJMoa2307563. https://www.nejm.org/doi/full/10.1056/NEJMoa2307563
  11. Jastreboff AM, et al. Triple–Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial. NEJM 2023;389:514–526. doi:10.1056/NEJMoa2301972. NCT04881760. https://www.nejm.org/doi/full/10.1056/NEJMoa2301972
  12. Frias JP, et al. Tirzepatide versus Semaglutide Once Weekly in Patients with Type 2 Diabetes (SURPASS-2). NEJM 2021;385:503–515.
  13. Kosiborod MN, et al. Semaglutide in Patients with Heart Failure with Preserved Ejection Fraction and Obesity (STEP-HFpEF). NEJM 2023;389:1069–1084.

Trial results / company announcements

  1. Eli Lilly. TRIUMPH-1 topline (May 21, 2026): 12 mg −28.3% at 80 weeks; 45.3% ≥30%; 65.3% BMI<30; −30.3% at 104 weeks (BMI≥35 extension). https://www.prnewswire.com/news-releases/lillys-triple-agonist-retatrutide-delivered-powerful-weight-loss-in-pivotal-phase-3-obesity-trial-302778859.html
  2. Eli Lilly. TRIUMPH-2/TRIUMPH-3 topline + Q1 2027 BLA plan (July 23, 2026). Reuters/CNBC: https://www.reuters.com/legal/litigation/lilly-announces-more-next-gen-obesity-drug-data-plans-q1-2027-fda-application-2026-07-23 ; https://www.cnbc.com/2026/07/23/eli-lilly-will-file-for-approval-of-retatrutide-obesity-drug-in-2027.html
  3. Eli Lilly. TRIUMPH-4 topline (Dec 11, 2025): 12 mg −28.7% at 68 weeks + OA pain relief. https://www.prnewswire.com/news-releases/lillys-triple-agonist-retatrutide-delivered-weight-loss-of-up-to-an-average-of-712-lbs-along-with-substantial-relief-from-osteoarthritis-pain-in-first-successful-phase-3-trial-302778859.html (via Pharmaceutical Journal: https://pharmaceutical-journal.com/article/news/phase-iii-retatrutide-study-demonstrates-30-weight-loss)
  4. Eli Lilly. SURMOUNT-1 publication press release (fat mass −33.9% vs lean −10.9%; ≥25%: 39.7% at 15 mg): https://www.prnewswire.com/news-releases/lillys-surmount-1-results-published-in-the-new-england-journal-of-medicine-show-tirzepatide-achieved-between-16-0-and-22-5-weight-loss-in-adults-with-obesity-or-overweight-301561327.html
  5. Eli Lilly. SURMOUNT-5 head-to-head (tirz −20.2% vs sema −13.7%; ≥25%: 47.5% vs 22.8%). Company announcement Dec 2024 (also summarized by ACC/industry media).
  6. Novo Nordisk. STEP 1/2/3/4/5 publications (see items 5–9); SELECT press release (17,604 pts; HR 0.80; −9.4% at 104 weeks). https://www.prnewswire.com/news-releases/adults-with-obesity-treated-with-semaglutide-2-4-mg-achieved-and-maintained-a-significant-amount-of-weight-loss-in-a-68-week-trial-301254177.html
  7. American College of Cardiology trial summaries (SURMOUNT-1, STEP 1, SELECT): https://www.acc.org/latest-in-cardiology/clinical-trials/2022/08/04/15/32/surmount-1 ; https://www.acc.org/latest-in-cardiology/clinical-trials/2021/02/18/19/23/step-1 ; https://www.acc.org/latest-in-cardiology/clinical-trials/2023/11/09/15/04/select

Pharmacology

  1. Coskun T, et al. Structural determinants of dual incretin receptor agonism by tirzepatide. PNAS 2022;119:e2116506119. https://www.pnas.org/doi/10.1073/pnas.2116506119
  2. Willard FS, et al. Tirzepatide is an imbalanced and biased dual GIP and GLP-1 receptor agonist. JCI Insight 2020;5:e140532. https://insight.jci.org/articles/view/140532
  3. El K, et al. The incretin co-agonist tirzepatide requires GIPR for hormone secretion from human islets. Nat Metab 2023;5:945–954. https://www.nature.com/articles/s42255-023-00811-0
  4. Min T, Bain SC. The role of tirzepatide, dual GIP/GLP-1 receptor co-agonist, in the management of type 2 diabetes. Cardiovasc Diabetol 2022;21:111. https://link.springer.com/article/10.1186/s12933-022-01604-7
  5. StatPearls — Tirzepatide (half-life ≈5 days; 39 aa; Tmax 8–72 h; CL/F 0.061 L/h). https://www.ncbi.nlm.nih.gov/books/NBK585056
  6. Jastreboff AM, et al. NEJM 2023 (retatrutide Ph2) — potency balance 8.9×/0.3×/0.4×; half-life ≈6 days; HR +6.7–6.9 bpm; LDL −20%. https://pubmed.ncbi.nlm.nih.gov/37366315
  7. Retatrutide review (mechanism; EC50 GLP-1R 0.775 nM, GCGR 5.79 nM; hepatic metabolism; no CYP interaction). PMC. https://pmc.ncbi.nlm.nih.gov/articles/PMC12190491
  8. A Comprehensive Review on the Pharmacokinetics and Drug Interactions of GLP-1 RAs and the Dual GLP-1/GIP RA (half-life table: exenatide 2.4 h; tirzepatide ≈120 h). PMC. https://pmc.ncbi.nlm.nih.gov/articles/PMC12052016

Muscle loss / body composition

  1. Preservation of lean soft tissue during weight loss induced by GLP-1 and GLP-1/GIP receptor agonists (STEP 1 DXA: 6.9 kg LST / 10.4 kg FM ≈40%; SURMOUNT-1 DXA: 5.6 kg LST / 15.9 kg FM ≈26%). PMC. https://pmc.ncbi.nlm.nih.gov/articles/PMC12536186
  2. Linge J, et al. Muscle Mass and GLP-1 Receptor Agonists. Circulation 2024 (state-of-the-art review; sema lean loss up to 40%, liraglutide up to 60%; muscle volume loss largely proportional to weight loss; reduced muscle fat infiltration). https://www.ahajournals.org/doi/10.1161/CIRCULATIONAHA.124.067676
  3. Changes in lean body mass with GLP-1-based therapies and mitigation strategies. Diabetes Obes Metab 2024;26(Suppl). https://dom-pubs.onlinelibrary.wiley.com/doi/10.1111/dom.15728
  4. DEXA guidance for GLP-1 users (25–45% lean fraction range across drugs). https://dexascan.com/blogs/news/dexa-scan-for-glp-1-users-why-a-baseline-and-follow-up-body-composition-scan-are-non-negotiable-on-semaglutide-or-tirzepatide

Regulatory

  1. FDA Drug Shortage Database entries (semaglutide removed Feb 21, 2025; tirzepatide resolved Dec 19, 2024, re-added Apr 2025 under injunction, again resolved late 2025/2026). https://www.accessdata.fda.gov/scripts/drugshortages/
  2. Frier Levitt. FDA Determines (Again) the Tirzepatide Shortage Is Resolved (503A/503B implications, grace periods, OFA v. FDA). https://www.frierlevitt.com/articles/fda-determines-again-the-tirzepatide-shortage-is-resolved-what-this-means-for-503a-and-503b-compounding
  3. Hendershot Cowart. FDA Update: Current Guidelines for Semaglutide and Tirzepatide Compounding (Feb 18/21, Mar 19, 2025 enforcement-discretion dates; OFA v. FDA 4:25-cv-00174). https://hchlawyers.com/blog/2025/march/fda-update-current-guidelines-for-semaglutide-an
  4. FDA Warning Letter — GLP-1 Solution (Sept 9, 2025): compounded retatrutide/semaglutide/ tirzepatide as unapproved new drugs & misbranded. https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/glp-1-solution-715883-09092025
  5. McDermott. FDA takes aim at misleading claims for compounded GLP-1 drugs (June 16, 2026: 25 warning letters to telehealth cos; 40+ late 2025). https://www.mcdermottlaw.com/insights/fda-takes-aim-at-misleading-online-claims-for-compounded-glp-1-drugs
  6. EMA PRAC meeting highlights (8–11 April 2024): no causal association between GLP-1 RAs and suicidal/self-injurious thoughts. https://www.ema.europa.eu/en/news/meeting-highlights-pharmacovigilance-risk-assessment-committee-prac-8-11-april-2024
  7. EMA EPAR — Mounjaro (tirzepatide indications: T2D + weight management BMI≥30 / ≥27+comorbidity; CHMP variation opinion Dec 11, 2025 for pediatric T2D extension). https://www.ema.europa.eu/en/medicines/human/EPAR/mounjaro
  8. EMA/WHO falsified Ozempic alerts; Serbian Intellectual Property Office warning (2024–25). https://www.zis.gov.rs/en/vesti/2024-forged-medicament-ozempic
  9. UCHealth. Fake weight loss drugs / ban on compounded versions (April 23, 2025). https://www.uchealth.org/today/what-to-do-about-fake-weight-loss-drugs-and-ban-on-compounded-versions
  10. CT Attorney General. Suit vs GLP-1 distributor (Triggered Brand) (2025). https://portal.ct.gov/ag/press-releases/2025-press-releases/attorney-general-tong-sues-glp-1-weight-loss-drug-distributor-triggered-brand
  11. Drugs.com. What is "retatrutide peptide" being sold online? (FDA warning letters Sept 9, 2025; risks). https://www.drugs.com/medical-answers/what-retatrutide-peptide-sold-online-3580909
  12. Allegheny County Health Dept / FDA campaign re: retatrutide poison-center exposures +265% (early 2026).

Testing

  1. Janoshik Analytical — Common GLP-1 peptide blind test product page (US$360; ID + amount
    • purity; mixture analysis; detection limit <1/20th usual dose; add-on services & prices; CAS/MW table). https://janoshik.com/pricelist/common-glp-1-peptide-blind-test-semaglutide-tirzepatide-and-retatrutide
  2. Janoshik — main site & verification portal. https://janoshik.com ; https://janoshik.com/verify
  3. Gold Standard Analytics — GLP-1 panels (HPLC 214 nm, MS identity, NPC, TFA/acetate, LAL endotoxin, USP <71>/<85>). https://www.goldstandardanalytics.com
  4. Multifactor Quality and Safety Analysis of Semaglutide Products Sold by Online Sellers (JMIR market surveillance: 14.37%/8.97%/7.7% content, +28.56–38.69% overfill). https://pmc.ncbi.nlm.nih.gov/articles/PMC11582493

Community / vendor guides (dosing conventions)

  1. Peptide reconstitution calculators (tirzepatide vial math, BAC water volumes): https://peptidecalcs.com/calculators/tirzepatide ; https://www.glunovabio.com/guides/how-to-reconstitute-tirzepatide-mixing-guide ; https://riteaid.com/tools/peptide-dosage-calculator ; https://shop.bodybuilding.com/blogs/tools-and-calculators/tirzepatide-dosage-calculator
  2. Retatrutide dosage guides (trial titration 2→4→6→9→12 mg; community 0.5–4 mg norms; reconstitution tables for 5/10/20/30 mg vials): https://pspeptides.com/blog/retatrutide-dosage-guide ; https://ro.co/weight-loss/retatrutide-dosing ; https://peptiq.io/blog/retatrutide-beginners-guide-reconstitution-dosing ; https://lolahealth.com/blogs/longevity/retatrutide-dose-escalation-chart ; https://www.youtube.com/watch?v=83M6RWKjzQY (community dosing analysis, gray-market pattern)
  3. r/RetatrutideGBP dosage protocol thread (start low, titrate by feel). https://www.reddit.com/r/RetatrutideGBP/comments/1kqp74a/retatrutide_dosage_protocol_how_to_dose_the

Market

  1. IQVIA. The outlook for obesity from 2026 to 2030 (US$66B 2025 → US$92B 2026 → US$105–200B 2027+). https://www.iqvia.com/locations/emea/blogs/2026/04/the-outlook-for-obesity-from-2026-to-2030
  2. TD Securities. GLP-1 Market: The Pipeline Expands (US$139B by 2030; 21% CAGR). https://www.tdsecurities.com/ca/en/glp1-market-the-pipeline-expands
  3. 2025 brand-level GLP-1 sales (Mounjaro US$39.1B, Zepbound US$22.9B, Wegovy US$18.6B; total ~US$132B) — IQVIA/AMCP 2026 figures compiled in industry stats pages. https://wellness.goalbmi.com/glp-1-statistics-2026
  4. Reuters. Ozempic/Wegovy picked for Medicare price negotiations (list prices: Ozempic ~US$935/mo, Wegovy ~US$1,350/mo). https://www.reuters.com/business/healthcare-pharmaceuticals/us-targets-novo-nordisks-diabetes-drug-ozempic-medicare-price-talks-2025-01-17
  5. NovoCare cash-pricing page (Wegovy US$349/mo standard doses, 2026) via healthcount.app US pricing tracker. https://www.healthcount.app/us/glp1-prices

12. Appendix — Math, Units, Glossary

12.1 Unit & concentration math (worked examples)

Formula: concentration (mg/mL) = peptide (mg) ÷ BAC water (mL) mcg per unit: (mg × 1000) ÷ mL ÷ 100 Dose in units: dose (mcg) ÷ mcg-per-unit

Example 1 — 30 mg tirzepatide + 3 mL BAC = 10 mg/mL.

  • 10 mg/mL = 10,000 mcg/mL = 100 mcg/unit (0.01 mL). 2.5 mg dose → 2,500 mcg → 25 units.

Example 2 — 20 mg semaglutide + 4 mL BAC = 5 mg/mL = 50 mcg/unit.

  • 1.0 mg dose → 1,000 mcg → 20 units. 0.25 mg → 5 units.

Example 3 — 30 mg retatrutide + 3 mL BAC = 10 mg/mL = 100 mcg/unit.

  • 2 mg dose → 2,000 mcg → 20 units. 4 mg → 40 units.

Overfill math: if COA says 31.4 mg measured in a "30 mg" vial, actual concentration is 10.47 mg/mL (31.4/3) → recalc units if you want exact dosing; the 5% error is acceptable for most research.

12.2 Syringe primer

  • U-100 insulin syringe: 100 units = 1 mL; ½-unit markings common on 0.3 mL syringes.
  • For sub-10-unit draws (semaglutide start doses), use a 0.3 mL (30-unit) syringe with half-unit marks — a 5-unit dose is drawable but error-prone on a 100-unit barrel.
  • Needle: 29–31 G, 4–8 mm ("insulin pen" length) for SC; larger gauge for reconstitution (drawing BAC).

12.3 Glossary

| Term | Meaning | |---|---| | RUO | Research use only — labeling frame, not a regulatory approval | | GLP-1 | Glucagon-like peptide-1; incretin hormone; satiety + insulin | | GIP | Glucose-dependent insulinotropic polypeptide; incretin hormone; fat metabolism | | GCG | Glucagon; counter-regulatory hormone; energy expenditure | | RA / co-agonist / tri-agonist | Receptor agonist; dual/triple receptor targeting | | Aib | α-aminoisobutyric acid (non-natural amino acid, DPP-4 resistance) | | DPP-4 | Enzyme that degrades native incretins (semaglutide/tirz/reta are DPP-4 resistant) | | Fatty diacid | Lipid tail that binds albumin → long half-life (C18 sema, C20 tirz/reta) | | Half-life (t½) | Time for plasma concentration to halve (sema ~7 d, tirz ~5 d, reta ~6 d) | | Steady state | ~4–5 weeks to reach; don't judge efficacy before this | | Titration | Stepwise dose increase (typically every 4 weeks) | | Maintenance dose | Dose that holds weight stable after goal reached | | Rebound | Weight regain after discontinuation (documented, large) | | EST/estimand | Efficacy vs treatment-regimen analysis approaches in trials | | MACE | Major adverse cardiovascular event (CV death, MI, stroke) | | HR (statistics) | Hazard ratio (SELECT: 0.80 = 20% risk reduction) | | DXA / DEXA | Dual-energy X-ray absorptiometry; body-composition gold standard | | LST / FFM / LBM | Lean soft tissue / fat-free mass / lean body mass | | FM | Fat mass | | NPC | Net peptide content (true peptide mass, salt-corrected) | | TFA | Trifluoroacetic acid (synthesis counterion; high = irritation) | | HMWP / dimer | High-molecular-weight proteins / aggregates; immunogenicity risk | | LAL | Limulus amebocyte lysate endotoxin test | | TAMC / TYMC | Total aerobic microbial count / total yeast & mold count | | 503A / 503B | US pharmacy compounding categories (individual Rx / outsourcing facility) | | OFA v. FDA | Outsourcing Facilities Association lawsuit over shortage-list removals | | ALIMS | Serbian medicines agency (Agencija za lekove i medicinska sredstva) | | PRAC | EMA Pharmacovigilance Risk Assessment Committee | | BLA / NDA | Biologics license application / new drug application (US) | | CagriSema | Novo's cagrilintide + semaglutide fixed combo (phase 3: −22.7% @ 68 wk) | | SURMOUNT / STEP / TRIUMPH / SURPASS / SELECT | Trial program names (Lilly tirz/reta; Novo sema) | | mcg/u | Micrograms per syringe unit (dosing convenience metric) |

12.4 Compliance boilerplate (for public pages)

For Research Use Only. Not for human or veterinary use. Tirzepatide, semaglutide and retatrutide are pharmaceutical-grade investigational/approved molecules supplied in lyophilized form as laboratory reagents for in-vitro and animal research. These products are not medical devices, not drugs, and are not intended to diagnose, treat, cure or prevent any disease. No efficacy, safety or dosing-for-humans claims are made. Buyers are responsible for compliance with all applicable local, national and international laws, including customs regulations.

End of module. Maintained by VALEN LABS Knowledge Base. Last updated: 2026-08-09. Review cadence: re-check regulatory section quarterly (FDA shortage list, EMA/ALIMS actions, retatrutide BLA status, Janoshik pricing) and trial data after each major topline release.