Compound guide · Tier B
Retatrutide
The largest weight loss figures ever published for an obesity drug, from a compound that is not approved anywhere and cannot be lawfully compounded.
The short answer
The trial record is exceptional and it will very likely be approved. Right now it is unapproved material with no legal supply route, roughly a year and a half before any regulator finishes reading the dossier. Both of those are true at once.
At a glance
| Class | Triple GIP, GLP-1 and glucagon receptor agonist |
| Developer | Eli Lilly |
| Sold as | No brand name. Investigational. |
| Regulatory status | Not approved by any national regulator. The Phase 3 TRIUMPH programme reported during 2026 and Lilly has stated it intends to file for approval in the first quarter of 2027. |
| Compounding status | There is no lawful compounding route in the United States under either section 503A or 503B, because retatrutide is not a component of any approved drug and has no pharmacopoeial monograph. This is not a shortage pathway that closed. There was never a pathway. |
| Anti-doping | Captured by S0, which prohibits at all times any substance not approved by a government regulatory authority for human therapeutic use. No therapeutic use exemption is available. |
| Our evidence tier | Tier B. Human trial data, not approved |
What it is
Retatrutide activates three receptors: GIP, GLP-1 and glucagon. The glucagon arm is the novel part. Glucagon receptor agonism increases energy expenditure, which is a different lever from the appetite and gastric emptying effects that drive the single and dual agonists, and is the leading explanation for the larger weight loss observed.
Who it is for, and who actually takes it
No approved indication exists. In trials the studied populations are adults with obesity, with and without type 2 diabetes, and with a range of obesity-related conditions.
There is no approved population, so everyone obtaining retatrutide outside a clinical trial is doing so through the grey market. Search interest has grown to roughly the same order as the two approved drugs, which tells you how large that market has become.
What the research shows
Mean weight change at 80 weeks, TRIUMPH-1
Adults with obesity and without diabetes, n=2,339, randomised to placebo or one of three retatrutide doses.
View as table
| Group | % mean weight loss |
|---|---|
| Placebo | 2.2% |
| 4 mg | 19.0% |
| 9 mg | 25.9% |
| 12 mg | 28.3% |
Source: Eli Lilly topline announcement, May 2026.
Adverse events at 12 mg against placebo
Participants reporting each event in TRIUMPH-1. The efficacy above and the side effects here come from the same trial at the same dose.
View as table
| Event | Retatrutide 12 mg | Placebo |
|---|---|---|
| Nausea | 42.4% | 14.8% |
| Diarrhoea | 32.0% | 13.5% |
| Vomiting | 25.3% | 4.8% |
| Dysesthesia | 12.5% | 0.9% |
Source: Eli Lilly topline announcement, May 2026.
Dosing
There is no approved dosing schedule for retatrutide, because there is no approval. The doses studied in TRIUMPH-1 were 4 mg, 9 mg and 12 mg once weekly, reported here as parameters of the trial and nothing more. Discontinuation in the trial rose with dose, from 4.1% at 4 mg to 11.3% at 12 mg against 4.9% on placebo, so the highest dose was also the least tolerated. We publish no schedule, no escalation and no reconstitution guidance for this compound.
What happens when you come off it
No published discontinuation study exists for retatrutide specifically. The pattern across this drug class is consistent and there is no mechanistic reason to expect retatrutide to behave differently: weight returns after treatment stops. Anyone assuming otherwise is assuming something the evidence does not currently support either way.
What it is being studied for
| Area | Stage of evidence |
|---|---|
| Obesity and overweight | Phase 3, several complete |
| Type 2 diabetes | Phase 3, several trials |
| Knee osteoarthritis pain in obesity | Phase 3, complete |
| Obstructive sleep apnoea | Phase 3, within obesity trials |
| Cardiovascular disease | Phase 3, complete |
| Atherosclerotic cardiovascular disease with chronic kidney disease | Phase 3, active |
| Chronic low back pain | Phase 3, active |
| Fatty liver disease, MASLD | Phase 3, recruiting |
A search of ClinicalTrials.gov on 7 September 2026 returns 33 registered retatrutide studies, 14 of them Phase 3. Read that list as a set of open questions, not a list of uses. A registered trial in chronic low back pain means someone thought the hypothesis worth testing, not that retatrutide treats back pain.
Common myths
It is approved somewhere, just not here.
It is approved nowhere. Not the FDA, EMA, MHRA, TGA or SAHPRA. A filing is expected in the first quarter of 2027, which is a filing, not an approval.
A compounding pharmacy can legally make it.
It cannot. With no approved drug containing it and no pharmacopoeial monograph, retatrutide qualifies under neither 503A nor 503B. Any pharmacy offering it is operating outside that framework.
It is just a stronger tirzepatide.
It adds a third receptor. Glucagon agonism raises energy expenditure, which is a mechanism neither semaglutide nor tirzepatide has.
A clean certificate of analysis means it is safe to use.
A certificate can establish that a batch was pure and correctly identified when tested. It cannot establish sterility, endotoxin levels, the dose in your vial, the storage and shipping afterwards, or that your vial came from the tested lot.
Phase 3 success means it is proven safe.
Phase 3 success means the sponsor believes the dossier supports approval. The regulator has not yet examined it. That review is precisely the step that has not happened.
Verifying a purchase
Retatrutide has no pharmacopoeial monograph, which means there is no official reference standard for a laboratory to test against. Confirm the observed mass against the stated molecular formula yourself. Because it is unapproved and in high demand, substitution with cheaper tirzepatide is a realistic failure mode that only mass spectrometry will catch, and purity alone will not.
The general method is set out in our guide to reading a certificate of analysis, which covers the eleven checks that apply to any compound. The points above are the ones specific to Retatrutide.
Caveats and safety
In TRIUMPH-1 at 12 mg, nausea affected 42.4% of participants against 14.8% on placebo, diarrhoea 32.0% against 13.5%, vomiting 25.3% against 4.8%, and dysesthesia 12.5% against 0.9%. Dose-dependent heart rate increases have been reported in earlier trial work for this compound. Because it is unapproved, there is no pharmacovigilance system, no recall mechanism and no liability route covering material bought outside a trial.
Where to get it
Where to get it
CertaPeptides Romania, EU. Volume discounts at 3+, 5+ and 10+ units.
| Vial | Price |
|---|---|
| 2 mg | from €44.49 |
| 5 mg | €44.49 |
| 10 mg | €69.99 |
| 20 mg | €118.99 |
| 50 mg | €275.99 |
| 60 mg | listed |
Stated purity. ≥98% stated batch specification. Published lot report #212146 returned 99.85% on a 20 mg vial.
Documentation. Selected lots independently tested by Janoshik Analytical (Czech Republic), HPLC plus mass spectrometry, reports searchable on the Janoshik public portal and at certapeptides.com/verify.
Retatrutide is sold as laboratory research material. The vendor states it is not for human consumption and that it is not approved by the FDA, the EMA or any other regulator for use in humans or animals. Read the evidence tier at the top of this page before the price.
View Retatrutide at CertaPeptidesAffiliate link. We earn a commission if you buy, at no extra cost to you. It does not change a word of the assessment above. Every product we have priced, in one list.
Sources
- Eli Lilly, TRIUMPH-1 topline results, May 2026
- Eli Lilly, what to know about retatrutide
- TRIUMPH-1 registration, NCT05929066
- ClinicalTrials.gov registry, queried 7 September 2026
Related compounds
Disclosure. PeptoPurity is an affiliate of CertaPeptides and earns a commission on qualifying purchases made through the vendor link on this page, at no additional cost to you. That relationship does not set the evidence tier, alter the verdict, or change a word of the assessment. Our Tier C and Tier D pages carry the same links as our Tier A pages, with the same conclusions we would publish if we earned nothing. Where the registered, prescribed route is the better option, we say so on the page that would otherwise pay us.
Scope. This is an evidence review, not medical advice. Where an approved label schedule is reproduced it is a record of what a regulator has published about a licensed medicine, not a recommendation and not a schedule for anyone to follow unsupervised. For unapproved compounds we report only the doses used in published studies, attributed to those studies, and we publish no protocols and no reconstitution guidance for any compound. Regulatory status differs between countries and changes over time. Material sold for laboratory research is not approved for human use. Decisions about treatment belong with a qualified prescriber.