Retatrutide vs tirzepatide
These two are often mentioned together because they come from the same company and the same drug family. The key differences are how many receptors each one targets and how far along each one is. This guide lays both out plainly.
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Retatrutide vs tirzepatide at a glance
| Tirzepatide | Retatrutide | |
|---|---|---|
| Receptors | GLP-1 + GIP | GLP-1 + GIP + glucagon |
| Type | Dual agonist | Triple agonist |
| Dosing | Once weekly | Once weekly (in trials) |
| Maker | Eli Lilly | Eli Lilly |
| Status | Approved (Mounjaro, Zepbound) | Investigational, Phase 3 |
How they work differently
Tirzepatide switches on two receptors, GLP-1 and GIP. Together these lower appetite, slow the stomach and improve blood-sugar control. Retatrutide does all of that and adds a third signal, the glucagon receptor, which raises energy expenditure and helps break down stored fat. That extra glucagon action is the whole reason retatrutide exists as a separate compound. For the full mechanism, see how does retatrutide work.
What do the trials show?
Tirzepatide is supported by a large completed trial programme and produced average weight reductions of around 20 percent in its obesity studies. Retatrutide, in a Phase 2 trial published in the New England Journal of Medicine in 2023, was associated with an average reduction of about 24 percent at 48 weeks at the highest dose, and its Phase 3 TRIUMPH trials in 2025 and 2026 reported figures in a similar or higher range. Because the two have not been compared directly in the same trial, these numbers come from separate studies with different designs.
An educational summary of published clinical research. Cross-trial numbers are not a direct comparison and are not a claim about any individual.
Which one is stronger?
On the trial averages, retatrutide has shown larger weight reduction, which fits its extra glucagon target. But stronger is not a simple label. The trials differ, tirzepatide has years of real-world use behind it while retatrutide does not, and response varies between people. The fair summary is that retatrutide looks more powerful in early data, and tirzepatide is the proven, approved option today.
Approval status of each
Tirzepatide is an approved medicine. Retatrutide is not, and remains in Phase 3 trials as of August 2026, with an approval filing expected around early 2027. For the detail, see is retatrutide FDA approved.
References
- Jastreboff AM, Kaplan LM, Frias JP, et al. Triple-Hormone-Receptor Agonist Retatrutide for Obesity - A Phase 2 Trial. N Engl J Med. 2023;389(6):514-526. PMID 37366315.
- Retatrutide (LY3437943) Phase 3 TRIUMPH program. ClinicalTrials.gov. Trial records.
- Jastreboff AM, Kaplan LM, Hartman ML. Triple-Hormone-Receptor Agonist Retatrutide for Obesity. Reply. N Engl J Med. 2023;389(17):1629-1630. PMID 37888927.
Frequently asked questions
Is retatrutide better than tirzepatide?
In early trial data retatrutide showed larger average weight reduction, in line with its extra glucagon target. But the two have not been compared head to head, and tirzepatide is the approved, proven option today.
What is the difference between retatrutide and tirzepatide?
Tirzepatide targets two receptors (GLP-1 and GIP) and is approved. Retatrutide targets three (GLP-1, GIP and glucagon) and is still investigational.
Are retatrutide and tirzepatide made by the same company?
Yes. Both are developed by Eli Lilly.
Is retatrutide approved like tirzepatide?
No. Tirzepatide is approved. Retatrutide is still in Phase 3 trials and is not approved as of August 2026.