Dosing, results, side effects and trials
Retatrutide, explained.
Eli Lilly's GIP, GLP-1 and glucagon triple agonist in plain English. Every number on this site links to the study it came from.
- 28.3% average weight loss at 80 weeks on 12 mg (Phase 3, TRIUMPH-1)
- 24.2% at 48 weeks in the Phase 2 trial (338 adults)
- Still investigational: no approved version exists yet
Dose to syringe units
U-100 syringeIn TRIUMPH-1, people on 12 mg lost an average of
of their body weight in 80 weeks
Source: Eli Lilly and Company (via PR Newswire), 2026. Phase 2 for comparison: 24.2% at 48 weeks (NEJM 2023).
What the trial average would mean at your start weight
Based on the 12 mg, 80 weeks (TRIUMPH-1) average of 28.3%. A trial average, not a prediction for any one person. Results vary with dose, adherence and starting weight.
Open the weight-loss calculatorEvery claim is sourced. Every page shows when it was last checked.
Start with the question you have
Guides organized the way people actually search, with new ones added every week.
- How Long Do Retatrutide Side Effects Last? What the Trials Show
- Retatrutide Injection Site Reactions
- Retatrutide Insomnia
- Retatrutide Nausea and Vomiting
Retatrutide at a glance
The short version, with the sources underneath.
Retatrutide is an experimental weight-loss medicine from Eli Lilly and Company, taken as a once-weekly injection under the skin. It is one molecule that switches on three hormone receptors at the same time: GIP, GLP-1 and glucagon. That is why it gets called a triple agonist, and online, "reta" or "GLP-3".
| Topic | What we know |
|---|---|
| What it is | A triple hormone receptor agonist (GIP, GLP-1 and glucagon) |
| Made by | Eli Lilly and Company (trial code LY3437943) |
| How it is taken | A once-weekly injection under the skin, started low and raised in steps |
| Status | Investigational and still in Phase 3 trials. No approved version exists yet |
| Phase 2 weight loss | 24.2% average at 48 weeks on 12 mg, versus 2.1% on placebo (338 adults) |
| Phase 3 weight loss | 28.3% average at 80 weeks on 12 mg in TRIUMPH-1 |
| Most common side effects | Nausea, diarrhea, vomiting and constipation, mostly mild to moderate and dose-related |
GLP-1 and GIP are gut hormones that help you feel full and keep blood sugar in check. Glucagon mostly acts on the liver. Tirzepatide works on the first two; retatrutide adds the third.
The catch is that nothing about it is approved yet. If you are comparing retatrutide for sale online, remember that without an approved product the quality of what arrives rests entirely on the seller's own testing.
Sources: the Phase 2 trial in the New England Journal of Medicine and Eli Lilly's TRIUMPH-1 topline announcement.
Latest guides
Written against the published trial data and updated when new results land.
- Retatrutide and Fatty Liver (MASLD)Conditions · 8 min read
- How Long Do Retatrutide Side Effects Last? What the Trials ShowSide Effects · 8 min read
- Retatrutide Injection Site ReactionsSide Effects · 8 min read
- Retatrutide InsomniaSide Effects · 9 min read
- Retatrutide Nausea and VomitingSide Effects · 8 min read
Frequently asked questions
What is retatrutide?
Retatrutide is an investigational once-weekly injection from Eli Lilly and Company. It is a single molecule that activates three hormone receptors, GIP, GLP-1 and glucagon, and it is being tested for obesity, type 2 diabetes and related conditions.
Is retatrutide FDA approved?
No. Retatrutide is still in Phase 3 clinical trials and no approved version exists yet in the US or anywhere else.
How much weight do people lose on retatrutide?
In the Phase 2 trial, people on 12 mg lost an average of 24.2% of their body weight after 48 weeks, compared with 2.1% on placebo. In the Phase 3 TRIUMPH-1 trial, the 12 mg group lost an average of 28.3% over 80 weeks.
How is retatrutide taken?
In the trials it is injected under the skin once a week. Treatment starts at a low dose that is raised in steps, which the Phase 2 trial found reduced stomach side effects.
What are the most common side effects of retatrutide?
Gastrointestinal effects such as nausea, diarrhea, vomiting and constipation. In the Phase 2 trial they were dose-related, mostly mild to moderate, and less frequent when treatment started at 2 mg instead of 4 mg. Heart rate also rose with dose, peaking at 24 weeks before easing.
Who makes retatrutide?
Eli Lilly and Company, the maker of tirzepatide (Mounjaro and Zepbound). Its trial code is LY3437943, and people online often call it reta or GLP-3.