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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)?
The world's first triple agonist weight loss drug — how it works, what the trials show, and why people call it GLP-3.
Updated August 11, 2026
How Does Retatrutide Work? Mechanism of Action Explained
The world's first triple agonist explained — how GLP-1, GIP, and glucagon receptors work together to reduce appetite and increase energy expenditure.
Updated June 2026
Retatrutide Results and Review: The Weight Loss Data by Dose
28.3% average weight loss at 80 weeks in the pivotal Phase 3 trial — here's the full data breakdown by dose, timeline, and what individual results look like.
Updated August 18, 2026
Retatrutide Side Effects & Safety Data (2026)
Trial incidence for retatrutide (reta) side effects — GI rates, dysesthesia, and class-level safety concerns.
Updated July 23, 2026
Retatrutide vs Tirzepatide (Zepbound): Triple Agonist vs Dual Agonist
Retatrutide produces 28.7% weight loss (triple agonist) vs tirzepatide's 22.5% (dual agonist). A head-to-head trial is underway.
Updated August 11, 2026
Retatrutide Phase 3 Results 2026: TRIUMPH Trial Tracker
Living tracker of every retatrutide trial — TRIUMPH-1/2/3/4/5, TRIUMPH-Outcomes, TRANSCEND-T2D-1/2, and SYNERGY-OUTCOMES Phase 3 readouts.
Updated August 1, 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 July 25, 2026
Does Retatrutide Cause Muscle Loss?
The first DXA body composition data for retatrutide, the glucagon muscle-sparing hypothesis, and evidence-based strategies to preserve lean mass.
Updated July 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 July 22, 2026