Retatrutide: Triple GIP/GLP-1/glucagon agonist (investigational)
An investigational once-weekly 'triple agonist' (GIP/GLP-1/glucagon) that produced very large weight loss in a Phase 2 trial — not yet FDA-approved.
What is Retatrutide?
Retatrutide is an investigational once-weekly injectable that activates three receptors — GIP, GLP-1 and glucagon. It is not FDA-approved and remains in clinical development, but its Phase 2 obesity results were among the largest reported for any weight-loss agent. Any retatrutide sold outside a clinical trial is an unapproved research compound.
How Retatrutide works (mechanism)
By adding glucagon-receptor activity to the GIP/GLP-1 incretin effects, retatrutide is thought to combine appetite reduction and improved glucose handling with increased energy expenditure. In the 48-week Phase 2 trial, mean weight reduction reached about 24% at the 12 mg dose, with 83% of that group losing ≥15% of body weight [1].
Why it's studied / reported uses
Obesity (investigational)
The Phase 2 obesity trial showed large, dose-dependent weight loss over 48 weeks [1]. Phase 3 development is ongoing; this is not yet an approved treatment.
Metabolic liver disease (research)
Retatrutide has also been studied in a Phase 2a trial for metabolic-dysfunction–associated steatotic liver disease (MASLD), reflecting interest in its metabolic effects beyond weight [2].
Dosing reported in studies
Route: subcutaneous
Higher arms started at 2 mg and escalated every 4 weeks for tolerability.
Route: subcutaneous
Starting at 2 mg produced fewer GI effects at equal 48-week weight loss.
Sources: Jastreboff et al. (2023) — N Engl J Med (Phase 2)
An investigational triple GIP/GLP-1/glucagon agonist. Not FDA-approved; still in clinical development. These figures reflect what studies or protocols reported — not a recommendation and not tailored to you.
Calculate a dose in the reconstitution calculator →Safety & side effects
In trials the most common adverse events were gastrointestinal (nausea, diarrhoea, vomiting), dose-related and mostly mild-to-moderate, and partly reduced by a lower 2 mg starting dose. Dose-dependent increases in heart rate were observed, peaking around 24 weeks. Because retatrutide is investigational, its full safety profile is not yet established, and it has no approved human use. It should only be used within a supervised clinical trial.
Studies & references
- Triple–hormone-receptor agonist retatrutide for obesity — a Phase 2 trial — PubMed 37366315 (Jastreboff et al., NEJM 2023)
- Retatrutide for metabolic-dysfunction–associated steatotic liver disease (Phase 2a) — NCBI / PMC11271400
Frequently asked questions
Is retatrutide FDA-approved?
No. Retatrutide is investigational and still in clinical development. Any retatrutide sold outside a clinical trial is an unapproved research compound.
How much weight loss did retatrutide cause?
In the Phase 2 obesity trial, mean weight loss reached about 24% at 48 weeks on the 12 mg dose — among the largest reported for a weight-loss agent. These are trial results, not a guarantee.
How is retatrutide dosed in trials?
Trials used 1, 4, 8 or 12 mg once weekly, with higher arms starting at 2 mg and escalating every 4 weeks to limit nausea (see the dosing section). This is trial dosing, not a recommendation.
What makes retatrutide different?
It targets three receptors (GIP, GLP-1 and glucagon) rather than one or two, which is thought to add an energy-expenditure effect on top of appetite reduction.
⚠ Research & educational use only. This page is compiled from published research and does not constitute medical advice. Retatrutide is investigational and not FDA-approved — still in clinical development. Nothing here is a recommendation to use or a prescription. Safe use can only be determined by a licensed physician. Last updated 2026-07-06.