Retatrutide is a synthetic peptide that activates three hormone receptors at once — GLP-1, GIP, and glucagon. Eli Lilly is developing it through the Phase 3 TRIUMPH program for obesity and metabolic dysfunction. Phase 2 trial data in NEJM showed weight-loss outcomes that exceed both tirzepatide and semaglutide. It is not yet FDA-approved.
Research notes
How does Retatrutide work?
Retatrutide is a synthetic peptide that activates three distinct hormone receptors at once: GLP-1 (glucagon-like peptide-1), GIP (glucose-dependent insulinotropic polypeptide), and glucagon. The combination is what makes it different from tirzepatide (dual GLP-1 / GIP) and semaglutide (GLP-1 only).
The third agonism — glucagon — is the source of both the larger weight-loss effect observed in trials and the metabolic side-effect profile that's still being characterized in Phase 3.
What doses are used in research?
Phase 2 studies escalated from 1 mg weekly through 12 mg weekly over 24 weeks. The dose-response curve in published data is roughly linear through 8 mg, with diminishing returns above. Half-life of approximately six days supports weekly dosing.
What does this guide cover?
Vendor audits for retatrutide focus on COA-verified purity and identity, since the molecule is novel enough that some grey-market vendors have shipped under-purity or misidentified material in early 2026. Cross-lab agreement on retatrutide samples is the single highest-weighted factor in our scoring for this compound.
What it's researched for
- weight loss
- metabolic dysfunction
- fatty liver
Where to source it
ALL 10 VENDORS →RANKED BY COMPOSITE SCORE · PRICES ARE SNAPSHOTS FROM THE PRICE INDEX · PER-MG IS A WITHIN-COMPOUND COMPARATOR
Frequently asked about Retatrutide
What is retatrutide?
Retatrutide is a synthetic peptide developed by Eli Lilly that activates three distinct hormone receptors at once: GLP-1 (glucagon-like peptide-1), GIP (glucose-dependent insulinotropic polypeptide), and glucagon. It is in the company's Phase 3 TRIUMPH trial program for obesity and related metabolic indications.
How is retatrutide different from tirzepatide?
Tirzepatide is a dual agonist (GLP-1 and GIP). Retatrutide adds a third agonism — glucagon — which is the source of both the larger weight-loss effect observed in trials and the metabolic side-effect profile that's still being characterized in Phase 3.
Is retatrutide FDA-approved?
No. Retatrutide is in Phase 3 development as of 2026 and has not been approved by the FDA, EMA, or any regulator. Anyone selling retatrutide today is selling unregulated research-grade material; it is not available as a prescription medication.
What doses are used in retatrutide research?
Published Phase 2 dose-escalation studies (NEJM, 2023) tested 1 mg, 4 mg, 8 mg, and 12 mg weekly subcutaneous. The compound has a half-life of approximately 6 days, which is consistent with once-weekly dosing.
What is the typical purity of research-grade retatrutide?
Janoshik Analytical tests in our corpus typically show 97–99% purity by HPLC for retatrutide from audited vendors, with identity confirmed by mass spectrometry. Per-vendor purity and any flagged lots are visible in the leaderboard on this page.