Investigational triple-agonist peptide (GLP-1/GIP/glucagon) developed by Eli Lilly, researched for metabolic regulation, weight management, and glucose control.
Last Updated: May 2026
Retatrutide, also designated LY3437943, is a 39-amino-acid investigational triple-receptor agonist activating GLP-1, GIP, and glucagon receptors. Developed by Eli Lilly and currently in the Phase 3 TRIUMPH program, retatrutide is not approved by the FDA or any other regulator for any indication and is supplied strictly for research use only. The lab test table and shop directory above show Peptigrity's independent verification data for retatrutide, updated continuously as new HPLC tests are submitted.
Retatrutide is the first triple GLP-1 / GIP / glucagon receptor agonist to reach Phase 3 clinical trials, distinguishing it from semaglutide (single GLP-1 agonist) and tirzepatide (dual GLP-1/GIP). The glucagon component is the new variable — in human trials, it appears to drive direct energy expenditure and hepatic fat clearance, mechanisms unavailable to single or dual agonists. The full receptor pharmacology, signaling pathways, and TRIUMPH-program design are covered in our retatrutide triple-agonist science guide.
In the May 2026 TRIUMPH-1 Phase 3 readout, retatrutide produced an average weight loss of 24.2% at the 12 mg dose over 80 weeks in adults with obesity, extending to 30.3% at 104 weeks. The earlier TRIUMPH-4 trial (December 2025) reported 28.7% average body weight loss at the 12 mg dose at 68 weeks in participants with obesity and knee osteoarthritis, alongside a 75.8% reduction in WOMAC knee pain scores. Five additional Phase 3 readouts across the TRIUMPH program are expected through late 2026. Evidence level: Human RCT (Phase 3 topline; peer-reviewed publication pending).
Retatrutide produces larger percent weight loss than either semaglutide or tirzepatide at matched trial durations, though no head-to-head Phase 3 data exists yet — TRIUMPH-5 is the active-comparator trial currently in progress. Tirzepatide reported approximately 22.5% weight loss in SURMOUNT-1 at 72 weeks; semaglutide reported 14.9% in STEP 1 at 68 weeks. Retatrutide's TRIUMPH-4 result of 28.7% at 68 weeks represents the highest weight-loss signal published for any compound in this class.
| Compound | Mechanism | Phase 3 weight loss | Regulatory status |
|---|---|---|---|
| Retatrutide | GLP-1 + GIP + glucagon (triple) | 28.7% — TRIUMPH-4, 68 wks, 12 mg | Investigational, no approvals |
| Tirzepatide | GLP-1 + GIP (dual) | 22.5% — SURMOUNT-1, 72 wks | FDA-approved (Mounjaro/Zepbound) |
| Semaglutide | GLP-1 (single) | 14.9% — STEP 1, 68 wks | FDA-approved (Ozempic/Wegovy) |
The most common retatrutide side effects in TRIUMPH-1 were dose-dependent nausea, dysesthesia, and urinary tract infection, all significantly more frequent at 12 mg than at 4 mg or placebo. The dysesthesia signal — a paraesthesia-like skin sensation — appears unique to retatrutide among the GLP-1 class and has been characterized across three Phase 3 populations (TRIUMPH-1, TRIUMPH-4, TRANSCEND-T2D-1). The full dose-by-dose adverse event breakdown, including the 104-week extension data, is in our retatrutide side effects guide. Evidence level: Human RCT (Phase 3).
Retatrutide is not approved for any indication, anywhere in the world, as of May 2026. Eli Lilly is pursuing FDA and EMA approval through the TRIUMPH program; NDA filing is contingent on the full Phase 3 readout package, with industry analysts estimating regulatory approval most plausibly in 2027–2028. Retatrutide is sold strictly as a research-use-only compound by third-party laboratories, with no approved prescription pathway. Country-specific import rules apply — see our peptide regulatory status by country guide.
Retatrutide's narrower manufacturing base, higher market price, and absence of an FDA-approved reference product create wider purity variance and stronger economic incentive for underdosing than older GLP-1 compounds. The triple-agonist synthesis adds complexity that fewer laboratories have optimized at scale. Independent HPLC purity testing and mass spectrometry identity confirmation (expected molecular weight 4,731.4 Da) are the only meaningful purity signals a research-grade vendor can provide. Learn how to interpret these in our how-to-test-peptides hub and the reading peptide lab test results guide.
Peptigrity purchases retatrutide vials anonymously at standard customer pricing, sends them to ISO-accredited third-party labs for HPLC and mass spectrometry analysis, and publishes the unedited certificate of analysis. The lab test table above this section shows the full cross-shop dataset, sortable by date, purity, and labeled-vs-tested quantity. Tests are sourced from named labs including Janoshik Analytical, Freedom Diagnostics, Chromate, Trust Pointe Analytics, and Krause Analytical. Our verification methodology — including the trust score weighting of reviews (50%) and lab purity (50%) — is documented in how we calculate trust scores.
The only reliable purity signal is an independent third-party HPLC certificate of analysis from a lab the vendor does not own or pay — not a vendor-published COA on vendor letterhead. Peptigrity publishes independent retatrutide test results from ISO-accredited labs in the table above. For COA interpretation, see red flags in peptide certificates of analysis.
Retatrutide is legal to purchase as a research chemical for laboratory use in most jurisdictions including the United States and most EU member states, but it is not approved for human consumption. Buyers are responsible for verifying local import rules — full country-by-country breakdown in our peptide legal status guide.
No FDA approval has been granted as of May 2026. Eli Lilly has reported topline results from two Phase 3 trials (TRIUMPH-4 in December 2025; TRIUMPH-1 in May 2026), with five more readouts expected through late 2026. Industry analysts estimate NDA filing in late 2026 with FDA approval most plausibly in 2027–2028. Track regulatory developments in FDA peptide regulation 2025–2026: the complete timeline.
Three factors: synthesis complexity (triple-agonist modification requires additional steps), narrower manufacturing base (fewer labs have optimized production at scale), and demand outpacing supply since the Phase 2 publication. Expect prices to fall as additional manufacturers come online post-TRIUMPH approval. Current research-grade market range is broken down in how much do peptides cost.
No. Retatrutide is not approved for human consumption and Peptigrity is an independent review platform, not a medical authority. The doses tested in Phase 3 (4 mg, 9 mg, 12 mg weekly) were administered under clinical supervision with full monitoring — translating these into a self-administration protocol is medical practice. Anyone considering use of investigational compounds should consult a licensed physician.
Retatrutide is currently the only Phase 3 triple agonist with reported weight-loss data. Other multi-receptor agonists in earlier-stage development include survodutide (GLP-1/glucagon dual) and mazdutide (GLP-1/glucagon dual). A full dual-vs-triple agonist comparison is planned for publication when TRIUMPH-2 and TRIUMPH-3 read out.
This section is for educational and informational purposes only and does not constitute medical advice. Retatrutide is an investigational compound not approved by the FDA or any other regulator for human use. Always consult a qualified healthcare provider before using any peptide or research compound. Peptigrity is an independent review platform and does not sell, endorse, or recommend specific products or vendors.
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