Reference, not advice. Retatrutide is an investigational drug. It is not approved anywhere, and all legitimate use takes place inside Eli Lilly's clinical trials. Tirzepatide is a prescription medicine. This page publishes no doses and gives no guidance on use. Vallydia does not sell, supply or link to either compound.
On the headline figure, retatrutide leads: about 28% weight loss at 80 weeks in the Phase 3 topline, against about 20–22% for tirzepatide in its own trials. But the two numbers sit at different stages of evidence, and the gap between them is the subject of this page.
The "research-use-only" retatrutide sold online is the reason this article exists. Its marketing rests on one leap: the trial results are real, so the vial must be too. It isn't. The register is explicit: gray-market retatrutide is unregulated, with unknown purity, sterility and dosing accuracy, and it is not the trial compound. The 28% figure belongs to the molecule Lilly made and tested under trial conditions. It does not transfer to a product of unknown origin.
| Outcome | Tirzepatide | Retatrutide |
|---|---|---|
| Weight loss in obesity | A – SURMOUNT, ~20–22%; SURMOUNT-5 head-to-head | B – Phase 2 (24.2% at 48 wk) + four Phase 3 toplines: TRIUMPH-1 28.3% at 80 wk, TRIUMPH-4 28.7% at 68 wk, TRIUMPH-2 20.8% (with type 2 diabetes), TRIUMPH-3 22.6% (with cardiovascular disease) |
| Glycaemic control in type 2 diabetes | A – SURPASS | B – TRANSCEND-T2D-1 topline |
| Liver fat / energy expenditure | Not graded | C – mechanistic and trial signals |
| Obstructive sleep apnea with obesity | A – SURMOUNT-OSA | Not graded |
| Cardiovascular risk reduction in type 2 diabetes | A – SURPASS-CVOT, vs dulaglutide (approved Aug 2026) | Not graded |
Why is the larger number graded lower? The grade measures how settled the evidence is, not how big the effect is. Tirzepatide's results are peer-reviewed, regulator-reviewed and approved. Retatrutide's Phase 3 results are, at the time of our last review, company-announced toplines. Full peer-reviewed data and regulatory review are still pending. The B grade says the effect is very likely real and not yet fully verified.
Retatrutide's distinguishing feature is the glucagon arm. GLP-1 and GIP reduce appetite and slow gastric emptying. Glucagon agonism is proposed to raise basal energy expenditure and reduce liver fat. Lilly attributes part of the unusually deep weight loss to this addition. Neither semaglutide nor tirzepatide has this arm. Its long-term effects, safety included, are still being characterised in Phase 3. That is why the register grades this outcome C.
| Semaglutide | Tirzepatide | Retatrutide | |
|---|---|---|---|
| Receptors | GLP-1 | GLP-1 + GIP | GLP-1 + GIP + glucagon |
| Weight, own trials | ~15% | ~20–22% | ~28% (topline) |
| Status | Approved | Approved | Investigational |
| Weight grade | A | A | B |
Each step up the ladder adds a receptor and adds weight loss. The last step also leaves approved territory.
Retatrutide is the fastest-moving entry in the register. Since our first review, TRIUMPH-2, TRIUMPH-3 and TRIUMPH-4 have also reported positive toplines, and Lilly plans to file with the FDA in the first quarter of 2027. They are still company announcements, so the grade stays B until full peer-reviewed data and a regulator's decision arrive. If retatrutide is approved, the comparison becomes an ordinary one between two prescription drugs. Until then, it is a comparison between a medicine and a trial result.
Is retatrutide better than tirzepatide? Its trial weight loss is larger: about 28% against about 20–22%. But retatrutide's Phase 3 data are topline only, and it is not approved. Tirzepatide's evidence is complete and approved.
Can I get retatrutide legally? Only by taking part in Eli Lilly's clinical trials. It has no approved prescription pathway anywhere.
Is "research peptide" retatrutide the same thing? No. It is unregulated, of unknown purity and sterility, and not the trial compound. None of the trial results apply to it.
When will retatrutide be approved? We do not forecast approvals. Lilly has said it plans to file with the FDA in the first quarter of 2027; the register will update when a regulator decides.
Does Vallydia publish doses? No. For an investigational drug there is no approved dose to publish.
Retatrutide's numbers are the most impressive in obesity pharmacology so far, and the register takes them seriously: B, trending up. Tirzepatide's numbers are smaller and finished. Between a larger effect that isn't yet confirmed and a smaller one that is, the register grades the confirmed one higher.
The biggest number in the room is not yet a licensed number.
See also Semaglutide vs Tirzepatide. Vallydia does not sell, supply or link to any GLP-1 medicine or investigational compound.
How we separate evidence levels: how we grade · how we grade.
Vallydia sells its own cosmetic serums, and some ingredients discussed here belong to the same categories as those products. Assessments are drawn from the published evidence by the method we publish, and applied to our own ingredients on the same terms — our copper-peptide serum is graded no more kindly than the peptides it competes with. We disclose the interest so you can weigh it.
Brand and trade names appearing in these articles are the property of their respective owners and are used only to identify the product or ingredient under discussion. Their appearance implies no affiliation with, or endorsement by, the proprietor. Where we judge a claim, we are judging the published evidence for that claim — not making a statement about the company that makes it.
A neutral reference and a lawful-lane shop. Information for those who seek it — never promotion.
This site provides neutral scientific reference and sells only products lawful in your region. Nothing here is medical advice, a recommendation, or an offer to supply unapproved medicines. No dosing or administration is published for research compounds. Cosmetic peptides per Regulation (EC) 1223/2009. Unapproved injectable peptides are neither sold nor advertised in the EU (Directive 2001/83/EC, Title VIII). © 2026 Vallydia.