Triple agonist (GIP, GLP-1 and glucagon) from Eli Lilly. Once-weekly injection. Average 28.3% weight loss at 80 weeks and 30.3% in a 104-week extension in TRIUMPH-1. Still phase 3. A US filing is expected around late 2026, so an approval is estimated for 2027 to 2028. You cannot buy it today.
What retatrutide is
Most weight-loss drugs on the market hit one or two gut hormones. Semaglutide (Wegovy, Ozempic) activates GLP-1. Tirzepatide (Zepbound, Mounjaro) activates GLP-1 and GIP. Retatrutide goes a step further and adds a third, glucagon.
Glucagon is best known for raising blood sugar, but at these doses the relevant effect is on energy use: it can nudge the body to burn more and helps clear fat from the liver. Pairing appetite suppression from GLP-1 and GIP with the energy-use effect of glucagon is the leading explanation for why retatrutide's trial weight loss ran higher than anything before it. It is given as a once-weekly injection.
The trial that made the headlines
In TRIUMPH-1, Lilly's phase 3 registration trial in obesity, the 12 mg dose produced an average 28.3% body-weight reduction at 80 weeks, roughly 70 pounds, compared with 2.2% on placebo. In a blinded extension, higher-BMI participants who stayed on 12 mg reached an average 30.3% at 104 weeks. No obesity drug had crossed 30% average in a phase 3 trial before. Earlier phase 2 results, published in the New England Journal of Medicine, had already pointed this way with about 24% at 48 weeks.
These are trial averages, not a promise for any one person. Weight loss in clinical trials runs alongside diet and activity changes, and results outside a trial setting are typically lower.
How it compares to what you can get now
The numbers below come from separate registration trials, not one head-to-head study, so read them as a rough ranking rather than an exact gap. The two approved drugs are on the GLP Chart comparison today; retatrutide is not.
| Drug | Hormones | Average weight loss | Trial | Status |
|---|---|---|---|---|
| Retatrutide | GIP + GLP-1 + glucagon | 28.3% (80 wk), 30.3% (104 wk ext.) | TRIUMPH-1 | Phase 3 |
| Tirzepatide (Zepbound) | GIP + GLP-1 | 20.9% at 15 mg (72 wk) | SURMOUNT-1 | Approved |
| Semaglutide (Wegovy) | GLP-1 | 14.9% (68 wk) | STEP 1 | Approved |
When you might actually get it
Retatrutide has finished its first phase 3 registration readout, but Lilly has not filed for approval yet. Reporting points to a US application around late 2026. If review runs the usual course, an approval is estimated for 2027 to 2028, and a launch would follow. Until then it is only available through clinical trials. Any telehealth program or pharmacy advertising retatrutide for sale right now is not offering an approved medicine, and we do not list it on the chart for that reason.
Side effects, so far
In clinical trials the most common side effects were gastrointestinal: nausea, diarrhea, vomiting and constipation, the same pattern across this whole drug class, mostly mild to moderate and tied to how fast the dose was raised. Because of the glucagon component, researchers watched heart rate and blood-sugar effects closely. The full safety picture in a wider population will not be settled until the larger phase 3 program reports and regulators review it.
Frequently asked questions
When will retatrutide be available?
How much weight did people lose on retatrutide?
Is retatrutide better than tirzepatide or semaglutide?
What is the third hormone retatrutide adds?
What are the side effects?
What you can get today
Retatrutide is still years away. The approved drugs, semaglutide and tirzepatide, are on the chart now across US telehealth programs, with prices checked every Monday. See the comparison chart, read about the rest of the pipeline, or browse the approved medications.
Sources: Lilly TRIUMPH-1 topline, AJMC, TRIUMPH-1 30.3%, NEJM, retatrutide phase 2
