Every line above is re-verified against the primary agency source before each update. What the July 2026 FDA vote did and did not do →
What retatrutide is
Retatrutide is an investigational peptide that activates three receptors — GIP, GLP-1 and glucagon. The added glucagon action is intended to raise energy expenditure alongside the appetite suppression the other two provide. It is given weekly by injection in trials.
What the trials report
A phase 2 trial in 338 adults over 48 weeks reported weight change from −8.7% to −24.2% across dose arms against −2.1% on placebo. The phase 3 TRIUMPH-1 trial enrolled 2,339 participants over 80 weeks and reported −19.0%, −25.9% and −28.3% across three dose arms against −2.2% on placebo, with 45.3% of the highest-dose group reaching at least 30% weight reduction. Two further phase 3 trials reported positive topline results in July 2026.
How to weigh those numbers
The phase 2 results are peer-reviewed. The phase 3 results are, as of now, company topline press releases — the trial designs and enrolment are confirmed on the public registry, but no regulator has reviewed the full dataset and no peer-reviewed publication exists. That is a meaningful distinction, and this guide keeps it visible rather than reporting all four figures as though they carried equal weight.
The gap between the science and the market
This is the substance where the distance between a promising trial programme and a lawful supply route is widest. There is no approved product to prescribe. FDA has stated it cannot be compounded. Anything offered for sale as retatrutide today sits entirely outside the approval system — and several of the FDA warning letters in our archive concern firms selling it, in some cases under coded names rather than the drug name.
How far up the evidence hierarchy this reaches
Genuine large randomised human trials, including a 2,339-participant phase 3 — but no approved label, and the phase 3 results are company reports rather than peer-reviewed publications.
Where it sits on the compounding pathway
What it is sold for, against what the evidence shows
Marketing claims on the left, in the terms sellers use. What the human literature actually supports on the right.
| Marketed for | What the evidence shows | Verdict |
|---|---|---|
| Very large weight loss | TRIUMPH-1, 2,339 participants, 80 weeks: up to −28.3% against −2.2% on placebo. | Supported |
| Improving blood sugar in type 2 diabetes | Reported in topline company results; not yet peer-reviewed or regulator-reviewed. | Partly supported |
| Fatty liver benefit | One randomised phase 2a trial. No published phase 3 liver outcome data. | Partly supported |
| "The next approved obesity drug — available now" | No approval exists anywhere and no licence application has been filed. Any product sold today is outside the approval system. | Contradicted |
| Legally compoundable like other GLP-1 drugs | FDA states it cannot be used in compounding under federal law. | Contradicted |
Where to go next
No dosing, cycling, stacking, reconstitution or administration instructions appear anywhere on this site, and this page links to no page selling an unapproved injectable. Questions about how a substance would be used belong with a licensed clinician who has evaluated you.
Sources
- Jastreboff AM et al. Triple–Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial. N Engl J Med, 2023
- ClinicalTrials.gov NCT05929066 — TRIUMPH-1
- FDA — concerns with unapproved GLP-1 drugs used for weight loss
- Sanyal AJ et al. Retatrutide for metabolic dysfunction-associated steatotic liver disease: a randomized phase 2a trial