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Retatrutide research
What it is, what the trials show, and how it affects your body.
See the overview on the homepage. Explore how retatrutide works, trial results by dose, side effects, treatment comparisons, and the trial program below.
What the trials showed
View statistics and sources →Trial means for people who stayed on treatment. Not FDA-approved; not a prediction for any one person.
The questions people ask first
- Is GLP-3 the same as retatrutide?
- Yes. GLP-3, GLP-3 RT and reta are nicknames for retatrutide (LY3437943), Eli Lilly's investigational triple agonist. There is no GLP-3 hormone.What retatrutide is →
- What does it do?
- It activates the GLP-1, GIP and glucagon receptors at once. In the pivotal Phase 3 trial the 12 mg arm averaged 28.3% weight loss at 80 weeks, and 45.3% of those participants lost 30% or more.Results by dose →
- Is it safe?
- There is no label yet. In the trials the common effects were gastrointestinal, plus skin tingling at 12 mg, which is why the dose climbs slowly. The larger risk today is unverified vials sold online.Side effects and safety data →
- How does it compare to tirzepatide?
- Three receptors against two. Retatrutide averaged 28.3% at 80 weeks in TRIUMPH-1; tirzepatide 22.5% at 72 weeks in SURMOUNT-1. Different trials, so a head-to-head, TRIUMPH-5, is running.Retatrutide vs tirzepatide →
- Can I get it?
- Not by prescription. A clinical trial is one route; since 3 August 2026 a clinician can also apply to Lilly's expanded access program for a narrow group. Online vials are not a route.How to get retatrutide →
- When will it be approved?
- Lilly plans to file in the first quarter of 2027. A standard review puts a first decision in late 2027 or 2028.The approval timeline →
Research by topic
What Is Retatrutide (GLP-3)?
Eli Lilly’s investigational triple receptor agonist: how it works, what trials show, and why GLP-3 is an informal nickname.
Updated September 8, 2026
How Does Retatrutide Work? Mechanism of Action Explained
How the three receptors work, and where proposed mechanisms go beyond demonstrated human effects.
Updated September 8, 2026
Retatrutide Results and Review: The Weight Loss Data by Dose
Dose-by-dose trial results, with timepoints, analysis differences and limits on predicting individual weight loss.
Updated October 1, 2026
Retatrutide (GLP-3) Side Effects & Safety Data (2026)
Separate trial tables for retatrutide GI effects and dysesthesia, with rare-event findings and current safety uncertainties.
Updated September 8, 2026
Retatrutide vs Tirzepatide (Zepbound): Triple Agonist vs Dual Agonist
How retatrutide and tirzepatide differ in receptor activity, trial evidence, safety, and approval status. Direct TRIUMPH-5 results are pending.
Updated September 8, 2026
Retatrutide Phase 3 Results 2026: TRIUMPH Trial Tracker
Trial results with population, endpoint, duration and source context. Use the trial finder for recruitment.
Updated October 2, 2026
Retatrutide FDA Approval Timeline 2026-2028
Lilly plans a Q1 2027 BLA filing. TRIUMPH-1, -2 and -3 have reported. Approval window late 2027–28.
Updated October 2, 2026
Does Retatrutide Cause Muscle Loss?
The DXA substudy measured fat and lean-mass reductions. It does not prove a muscle-sparing effect or establish outcomes for every patient.
Updated October 2, 2026
GLP-1 vs GLP-2 vs GLP-3: What's the Difference?
GLP-1 and GLP-2 are real hormones. "GLP-3" is not — it's slang for retatrutide. Here's what each term actually means.
Updated September 8, 2026