# Retatrutide A weekly injection that acts on three hormone receptors at once. It has produced the largest weight loss yet seen in phase 3 trials. Not approved anywhere, and heavily traded on the gray market. Also called: LY3437943, Triple G, Reta Source page: https://peplogue.com/peptides/retatrutide/ Updated: 2026-10-22. Not medical advice. ## How it works - Where it acts: GIP, GLP-1 and glucagon receptors. - What it changes: GLP-1 and GIP cut appetite. Glucagon adds energy use and pushes the liver to burn fat. - What people notice: In trials, the largest weight loss of any drug so far. Stomach side effects and a faster heart rate were reported. ## What the evidence shows - **Weight loss in obesity**: Supported. TRIUMPH-1 (2,339 people, 80 weeks): 28.3% average loss on 12 mg among people who stayed on it (2.2% on placebo), and 25.0% counting everyone (3.9% on placebo). - **Type 2 diabetes**: Supported. HbA1c fell 1.7 to 2.0 points at 40 weeks (TRANSCEND-T2D-1). Weight loss in diabetes was 20.8% at 80 weeks (TRIUMPH-2). - **Knee arthritis with obesity**: Supported. TRIUMPH-4 (445 people): 28.7% weight loss at 68 weeks on 12 mg, with less knee pain than placebo. - **Liver fat**: Early. An earlier phase 2 substudy found large falls in liver fat. No phase 3 liver result yet. ## Side effects and risks - serious: Abnormal skin sensations (tingling, burning, soreness to touch) in 12.5% of people on the top dose, against 0.9% on placebo. In one trial the figure was 20.9%. - serious: Vials sold online are unapproved and of unknown quality. FDA adverse-event reports rose from 10 in all of 2025 to 26 in the first five months of 2026. - common: Nausea in 42% and vomiting in 25% on the top dose. - common: About 11% stopped because of side effects, against 5% on placebo. - unknown: Long-term safety is still being studied. Whether it lowers or raises heart-attack risk is not known; the one trial that looked was too small to tell. Who should avoid it: Anyone outside a clinical trial. ## How it has been given in trials Weekly injection under the skin, stepped up over months to 4, 9 or 12 mg. There is no approved dose. ## Legal status - United States: undefined. FDA sent warning letters to sellers in August 2026. - European Union: undefined. No authorized product. - Spain: undefined. Investigational. No authorised product in Spain (not in CIMA). The only lawful route is a clinical trial; Spanish trial sites not verified. - Germany: undefined. Not authorised in Germany. Only available in clinical trials; sale outside trials is unlawful under the AMG (§ 21, § 96). German trial sites not checked. - France: undefined. Trials only. ANSM links it to hospitalisations and ordered a product sold as retatrutide (FastPen) removed on 14 Aug 2026. - Italy: undefined. Phase 3 only. Cannot legally be sold through any channel in Italy; research-labelled offers online are unverified. Italy launch unlikely before 2028. - Netherlands: undefined. Not authorised anywhere. IGJ banned a Dutch webshop from selling it in Aug 2026. Lareb received a report of serious harm after a retatrutide injection. - United Kingdom: undefined. MHRA raids since October 2025 have seized thousands of unlicensed weight-loss pens and doses, retatrutide among them. - Canada: undefined. Named in Health Canada advisories on unauthorized injectable peptides. - Australia: undefined. Seized in New South Wales raids in August 2026. ## Questions people ask **Is retatrutide FDA approved?** No. It is not approved anywhere, and a US filing is planned for early 2027. FDA sent warning letters to sellers in August 2026. **How much weight do people lose on retatrutide?** In TRIUMPH-1 (2,339 people, 80 weeks), average loss on the top dose was 28.3% among people who stayed on it and 25.0% counting everyone, against 2.2% and 3.9% on placebo. **What are the side effects of retatrutide?** On the top dose, nausea affected 42% and vomiting 25%. Abnormal skin sensations such as tingling, burning or soreness to touch affected 12.5%, against 0.9% on placebo, and about 11% stopped because of side effects. **Is it safe to buy retatrutide online?** Vials sold online are unapproved and of unknown quality, so the dose and even the contents are uncertain. FDA adverse-event reports rose from 10 in all of 2025 to 26 in the first five months of 2026. **Is retatrutide stronger than tirzepatide?** Its trials have produced the largest weight loss of any drug so far. Users outside trials report stronger appetite suppression than on tirzepatide, but they use unregulated products of uncertain dose and content. ## Sources - Eli Lilly: TRIUMPH-1 results (21 May 2026): https://investor.lilly.com/news-releases/news-release-details/lillys-triple-agonist-retatrutide-delivered-powerful-weight-loss - Eli Lilly: TRIUMPH-4 results (11 Dec 2025): https://investor.lilly.com/news-releases/news-release-details/lillys-triple-agonist-retatrutide-delivered-weight-loss-average - Eli Lilly: TRIUMPH-2 and TRIUMPH-3 results (23 Jul 2026): https://investor.lilly.com/node/54736 - Eli Lilly: TRANSCEND-T2D-1 results (19 Mar 2026): https://investor.lilly.com/news-releases/news-release-details/lillys-triple-agonist-retatrutide-demonstrated-significant - Finnrick: retatrutide test counts: https://www.finnrick.com/products/retatrutide - Frier Levitt: Lilly’s retatrutide lawsuits (18 Aug 2026): https://www.frierlevitt.com/articles/lilly-retatrutide-lawsuits-ruo-peptide-sellers/ - Health Canada: unauthorized injectable peptides (1 Aug 2025): https://recalls-rappels.canada.ca/en/alert-recall/unauthorized-injectable-peptide-drugs-seized-and-sold-canada-peptide-may-pose-serious - Pharmacy Daily: TGA peptide raids (18 Aug 2026): https://pharmacydaily.com.au/news/tga-in-peptide-melanotan-raids/122100 - MHRA: record seizure of illicit weight-loss pens (24 Oct 2025): https://www.gov.uk/government/news/mhra-smashes-majorillicitweight-loss-medicine-production-facility-in-record-seizure - Public Citizen: the retatrutide trade (16 Jun 2026): https://www.citizen.org/article/the-miracle-drug-and-the-peptide-craze-breaking-the-fda/ - FDA: concerns about unapproved GLP-1 drugs: https://www.fda.gov/drugs/postmarket-drug-safety-information-patients-and-providers/fdas-concerns-unapproved-glp-1-drugs-used-weight-loss