Retatrutide adds glucagon receptor agonism to the GLP-1/GIP dual mechanism of tirzepatide (Mounjaro). Here is how the two compounds compare on weight loss, mechanism, and research evidence.
Retatrutide is a triple GLP-1/GIP/glucagon receptor agonist. Tirzepatide (Mounjaro) is a dual GLP-1/GIP agonist. The addition of glucagon agonism in retatrutide increases hepatic fat mobilization and energy expenditure, producing greater weight loss in Phase 3 trials. Retatrutide is not yet FDA-approved.
| Feature | Retatrutide | Mounjaro (Tirzepatide) |
|---|---|---|
| Active molecule | Retatrutide | Tirzepatide |
| Mechanism | Triple GLP-1 + GIP + Glucagon agonist | Dual GLP-1 + GIP agonist |
| Brand name (Rx) | None yet — Phase 3 trials | Mounjaro (diabetes), Zepbound (obesity) |
| Avg weight loss (Phase 3) | ~24.2% body weight (TRIUMPH-1) | ~22.5% body weight (SURMOUNT-1) |
| GLP-1 activity | Full GLP-1 agonist | Full GLP-1 agonist |
| GIP activity | Full GIP agonist | Full GIP agonist |
| Glucagon activity | Full glucagon agonist | None |
| FDA approval | Not yet approved (Phase 3) | Approved 2022/2023 |
| Dosing frequency | Once weekly | Once weekly |
| Research availability | Available as research peptide | Available as research peptide |
Phase 3 data shows retatrutide produces slightly greater average weight loss than tirzepatide (Mounjaro) — approximately 24.2% vs 22.5% body weight. The addition of glucagon receptor agonism is believed to enhance energy expenditure beyond what dual GLP-1/GIP agonism achieves. However, retatrutide has not yet received FDA approval.
Tirzepatide (Mounjaro) activates GLP-1 and GIP receptors. Retatrutide activates GLP-1, GIP, and glucagon receptors — making it a triple agonist. The addition of glucagon receptor agonism increases energy expenditure and hepatic fat mobilization, which may explain retatrutide's superior weight loss outcomes in Phase 3 trials.
As of 2026, retatrutide is in Phase 3 clinical trials and has not received FDA approval. It is available as a research peptide. FDA approval is anticipated in 2026-2027 pending trial completion and regulatory review.
TRIUMPH-1 Phase 3 data showed retatrutide achieved approximately 24.2% body weight reduction vs 22.5% for tirzepatide in SURMOUNT-1. Both are superior to semaglutide (~15%). Retatrutide's glucagon agonism adds an energy expenditure component that tirzepatide lacks.
Purgo Labs carries both retatrutide and tirzepatide with third-party COAs. Use code HEALTH for 15% off.
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