Retatrutide: The Complete Guide
Retatrutide is the most effective obesity compound yet reported in a clinical trial, and it cannot be prescribed to anyone. Both halves of that sentence explain why it generates so much search traffic and so much bad information. This page is the overview; the detailed guides are linked below.
What makes it different
Incretin drugs are usually described by how many receptors they hit, and the count has been climbing:
| Compound | Receptor targets | Best trial result | Status |
|---|---|---|---|
| Semaglutide | GLP-1 | −14.9% at 68 weeks | Approved |
| Tirzepatide | GIP + GLP-1 | −20.9% at 72 weeks | Approved |
| Retatrutide | GIP + GLP-1 + glucagon | −30.3% at 104 weeks | Phase 3 |
The glucagon receptor is the addition that matters. GLP-1 and GIP activity work largely through appetite and satiety — they make eating less feel manageable. Glucagon activity increases energy expenditure and mobilizes fat from the liver, which adds a second mechanism rather than a stronger version of the first. That is the pharmacological argument for why the numbers are higher, and it is also why trials watched heart rate and liver enzymes more closely.
The results, in order
| Trial | Population | Duration | Weight reduction |
|---|---|---|---|
| Phase 2 | Obesity, n=338 | 48 weeks | −24.2% (12 mg) |
| Phase 2 | Type 2 diabetes | 36 weeks | −16.9% |
| TRIUMPH-1 | Obesity | 80 weeks | −28.3% |
| TRIUMPH-1 | Obesity | 104 weeks | −30.3% |
| TRIUMPH-3 | Obesity + OSA | 80 weeks | −22.6% |
One pattern is worth noticing across all of them: the weight curve had not flattened when Phase 2 ended at 48 weeks, and the longer Phase 3 follow-up kept descending. Earlier incretin trials plateaued considerably sooner.
Two caveats the chart cannot show. Trial durations differ — retatrutide's leading figure comes from 104 weeks against tirzepatide's 72, so some of the gap is time rather than potency. And every figure here is the treatment-policy estimand, which counts participants who stopped early; the larger numbers quoted in marketing are usually the trial-product estimand, which assumes perfect adherence.
What it is being tested for beyond obesity
The TRIUMPH program is broader than weight. Trials cover type 2 diabetes, obesity with knee osteoarthritis, and obstructive sleep apnea, and a separate Phase 2a trial reported an 81–82% relative reduction in liver fat in metabolic dysfunction-associated steatotic liver disease at the 8 and 12 mg doses. The liver finding is a direct consequence of the glucagon component.
The honest summary
Strongest published weight-loss results of any pharmacotherapy. No approval, no prescription pathway, no legal compounding route, and no long-term safety data beyond the trial windows completed so far. Everything sold online is research-grade material that no regulator has evaluated — which makes the supplier, not the molecule, the main variable in whether what you have is what the label says.
The detailed guides
Dosage & Titration
The doses used in Phase 2 and Phase 3, the four-week escalation schedule, and why the 6 mg step people share online was never in a trial.
Side Effects
What the trials reported by dose: gastrointestinal effects, heart rate, liver monitoring, and the lean-mass question.
Cost & How to Get It
Three routes — trial enrollment, waiting for approval, research suppliers — with real monthly cost by dose.
Where to Buy
How to vet a supplier: what a batch certificate of analysis must show, how to read HPLC and mass-spec results, red flags.
Retatrutide (RTA) — 10 mg — American Peptides
Not FDA approved; sold for laboratory research only. Our affiliate partner publishes HPLC and mass-spec results per batch — verify the COA for the batch you receive.
We may earn a commission if you buy through this link (at no extra cost to you). Sold for research purposes only.
Frequently asked questions
What is retatrutide?
Retatrutide is an investigational obesity and diabetes drug that activates three receptors at once — GIP, GLP-1 and glucagon. That third target, glucagon, is what distinguishes it from tirzepatide (two receptors) and semaglutide (one), and it is the main reason its weight-loss results are larger.
How much weight do people lose on retatrutide?
Phase 2 reported 24.2% mean body-weight reduction at 48 weeks on the 12 mg dose. Phase 3 TRIUMPH-1 went further with longer follow-up: 28.3% at 80 weeks and 30.3% at 104 weeks — the first obesity drug to cross 30% in a trial.
Is retatrutide better than tirzepatide?
On weight reduction alone, the trial numbers are higher — roughly 30% versus 21%. But tirzepatide is approved, has a far larger safety database, and can be prescribed. Retatrutide has stronger results and no approval, which is a genuine trade-off rather than a clear win.
When will retatrutide be available?
Eli Lilly has signalled a regulatory submission in early 2027, which realistically puts approval in late 2027 or 2028. Until then the only supervised access is a clinical trial.
Related reading
- Best peptides for weight loss, ranked by trial evidence
- Peptide reconstitution calculator
- Are peptides safe?