What retatrutide is
Retatrutide is an investigational "triple agonist." It activates three hormone receptors: GIP, GLP-1, and glucagon. It's taken once a week.
How it works
The GIP and GLP-1 actions reduce appetite and improve blood sugar control, like tirzepatide. The added glucagon action may increase how much energy the body burns and how much fat the liver uses, which researchers think could add to weight loss and liver health.
What the research shows
- TRIUMPH-1 (phase 3, 2026): in about 2,300 adults with obesity or overweight, average weight loss at 80 weeks was 19.0% on 4 mg, 25.9% on 9 mg, and 28.3% on 12 mg, compared with 2.2% on placebo. Nearly half (45%) of people on 12 mg lost 30% or more of their body weight. Counting everyone who started, including people who stopped treatment, the 12 mg average was about 25%.
- TRIUMPH-4 (phase 3, 2025): in adults with obesity and knee osteoarthritis, the 12 mg dose led to an average weight loss of 28.7% at 68 weeks, and knee pain scores dropped by about 75%.
- TRIUMPH-2 and TRIUMPH-3 (phase 3, 2026): average weight loss was about 13% to 21% in adults with type 2 diabetes, and about 22% to 23% in adults with severe obesity and heart disease, over 80 weeks.
- Earlier phase 2 trial (2023): 24.2% average weight loss at 48 weeks on 12 mg.
- Side effects: mostly stomach-related, like other GLP-1 medications, and more common at higher doses. In TRIUMPH-1, about 11% of people on 12 mg stopped because of side effects, compared with about 5% on placebo. Heart rate also rose in earlier trials.
- Still to learn: these phase 3 results were announced by the manufacturer, and full peer-reviewed publications are still to come.
Where it stands
Retatrutide is not FDA approved. Compounded retatrutide is prepared only under a patient-specific prescription with licensed prescriber supervision.
Lilly, the manufacturer, has said it plans to apply for FDA approval. Until then, there's less information about long-term effects than for semaglutide or tirzepatide. Talk with your prescriber about whether it makes sense for you, and about approved alternatives.
How dosing works
Compounded retatrutide is often prepared at 15 mg/mL with vitamin B6. Doses start low and step up about every four weeks.
Compounded retatrutide is often prepared at 15 mg/mL with vitamin B6 (pyridoxine) 10 mg/mL, for each patient under a prescription. Doses are measured with a standard U-100 insulin syringe.
| Vial size | Strength | Retatrutide per vial | Vitamin B6 per vial |
|---|---|---|---|
| 4 mL | 15 mg/mL | 60 mg | 40 mg |
| 10 mL | 15 mg/mL | 150 mg | 100 mg |
Typical dose schedule
- 2 mgWeeks 1–413 units
- 4 mgWeeks 5–827 units
- 6 mgWeeks 9–1240 units
- 9 mgWeeks 13–1660 units
- 12 mgWeek 17 on80 units
Increase only as directed by your prescriber. Hold or reduce the dose if stomach side effects occur. Maximum 12 mg weekly.
See every dose and how long a vial lasts
| Weekly dose | Amount | Syringe | 4 mL vial lasts | 10 mL vial lasts |
|---|---|---|---|---|
| 2 mg | ≈0.13 mL | 13 units | 30 wks | 75 wks |
| 4 mg | ≈0.27 mL | 27 units | 15 wks | 37 wks |
| 6 mg | 0.40 mL | 40 units | 10 wks | 25 wks |
| 9 mg | 0.60 mL | 60 units | 6 wks | 16 wks |
| 12 mg | 0.80 mL | 80 units | 5 wks | 12 wks |
Approximate supply, once weekly. Your prescriber sets your dose and any custom schedule.
Hold or reduce the dose if stomach side effects occur. The maximum dose is 12 mg weekly.
Sources
- Eli Lilly and Company. Topline results from the TRIUMPH-1, TRIUMPH-2, TRIUMPH-3, and TRIUMPH-4 phase 3 trials of retatrutide. Press releases, December 2025 to July 2026.
- Jastreboff AM, et al. Triple-hormone-receptor agonist retatrutide for obesity: a phase 2 trial. New England Journal of Medicine, 2023.
