Tirzepatide vs retatrutide at a glance
| Compared | Tirzepatide | Retatrutide |
|---|---|---|
| Brands | Zepbound, Mounjaro | None yet |
| Maker | Eli Lilly | Eli Lilly |
| Hormones copied | GIP and GLP-1 | GIP, GLP-1 and glucagon |
| Weight loss in main trial | 20.9% at 72 weeks (SURMOUNT-1) | 28.3% at 80 weeks (TRIUMPH-1) |
| Status | FDA-approved | Investigational; filing planned for 2027 |
How are tirzepatide and retatrutide different?
Tirzepatide copies two gut hormones, GIP and GLP-1; retatrutide adds a third, glucagon. Glucagon is thought to increase the energy the body burns and reduce liver fat, adding to the appetite effects.
Which causes more weight loss?
Retatrutide did in its trials: 28.3% average weight loss at 80 weeks in TRIUMPH-1, versus 20.9% at 72 weeks for tirzepatide in SURMOUNT-1. The trials weren’t head to head, so the gap is an estimate.
How do the side effects compare?
Both commonly cause nausea, diarrhea, vomiting and constipation, mostly while the dose is rising. Retatrutide trials also reported dysesthesia, a tingling or burning skin feeling.
Tirzepatide has been on the market since 2022, so its risks are better understood.
Which can you get now?
Tirzepatide, by prescription as Zepbound or Mounjaro. Retatrutide is only legally available in clinical trials; “research” retatrutide sold online is unapproved and unchecked.
The GLP-1 titration schedule shows tirzepatide’s label step-up, and each drug page lists its dosing with sources.