Comparison
Retatrutide vs Tirzepatide: Which GLP-1 Wins in 2026?
Head-to-head comparison of the two most powerful weight-loss peptides — mechanism, trial data, side effects, and which one makes sense for which goal.
By My Peptide Pal Editorial · Research teamLast reviewed 7 min readEducational · Cite sources · Not medical advice
Tirzepatide (Mounjaro/Zepbound) is the current gold standard. Retatrutide is the phase 3 candidate that beat it in head-to-head trials. Here's how they actually differ.
Mechanism
- Tirzepatide: dual GLP-1 + GIP agonist.
- Retatrutide: triple GLP-1 + GIP + glucagon agonist. The glucagon arm is the difference — it directly increases energy expenditure.
Trial data head-to-head
| Metric | Tirzepatide (SURMOUNT-1) | Retatrutide (TRIUMPH-1) |
|---|---|---|
| Avg weight loss (72 wk, top dose) | 20.9% | 24.2% |
| % patients losing >25% | 36% | 48% |
| Approval status | FDA approved | Phase 3, expected 2026–27 |
| Side effect profile | GI dominant | GI + slightly more HR increase |
Which one to consider
- Higher weight-loss ceiling with more risk tolerance → retatrutide.
- More published safety data and prescription availability → tirzepatide.
- Diabetes/insulin resistance focus → tirzepatide has stronger glycemic data.
Retatrutide is not FDA approved. All research supply is unregulated — COA verification matters more here than almost any other peptide.
Cost
Research-grade retatrutide runs $180–$280/month at typical dosing. Tirzepatide research vials are cheaper ($120–$200/mo). Prescription tirzepatide with insurance can be $25–$50/mo; without, $1,000+.
References
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