94 articles · updated weekly
Retatrutide (GLP-3), explained from the research
Plain-language answers on the triple-agonist weight-loss drug — how it works, side effects, dosing, and where the trials stand. Every claim cites a primary source, updated as new data lands.
NEJM
The Lancet
JAMA
FDA
ClinicalTrials.govWhat is GLP-3?
GLP-3 is not a real hormone or receptor. It is an informal consumer nickname for retatrutide (development code LY3437943), an investigational once-weekly injectable peptide from Eli Lilly. Retatrutide is a triple agonist: it activates GLP-1, GIP, and glucagon receptors at once. Peer-reviewed papers and FDA filings use “retatrutide” or “triple agonist,” not “GLP-3.”
People also search GLP-3 RT and GLP-3 reta — same drug. For the full mechanism and naming history, see What is retatrutide (GLP-3)? and GLP-1 vs GLP-2 vs GLP-3. Retatrutide is not FDA-approved as of July 2026.
| INN / name | Retatrutide (investigational) |
|---|---|
| Dev code | LY3437943 |
| Class | Triple agonist (GLP-1 + GIP + glucagon) |
| Developer | Eli Lilly |
| Phase | Phase 3 (TRIUMPH / TRANSCEND programs) |
| Peak trial weight loss | Up to ~24.2% at 48 wk (Phase 2 NEJM); ~28.3% at 80 wk (TRIUMPH-1 Phase 3 topline, May 2026) |
Weight-loss figures are trial means under protocol conditions, not guaranteed individual outcomes. This is educational only — not medical advice.
Featured
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
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 Dosage & Dosing Guide: Titration, Missed Doses, Taper
Phase 3 titration schedule (2→4→6→9→12 mg), missed-dose protocol, taper guidance, and dose-by-dose weight loss data.
Updated June 2026
Retatrutide essentials
See all →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 Brand Name: What Will It Be Called?
Eli Lilly hasn't announced a brand name for retatrutide yet. Expect it close to FDA approval in 2027.
Updated February 2026
Retatrutide Half-Life and Pharmacokinetics
Retatrutide has a ~6-day half-life achieved through fatty acid albumin binding — comparable to semaglutide (~7 days) and tirzepatide (~5 days).
Updated July 2026
Can You Build Muscle on Retatrutide?
Retatrutide is not anabolic. How testosterone and GH peptides — not retatrutide — build the physiques in viral transformation posts.
Updated June 2026
Microdosing Retatrutide & GLP-1 Drugs: What the Research Shows
Current evidence on sub-therapeutic dosing and dose-splitting of GLP-1 receptor agonists.
Updated July 2026
Drug comparisons
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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 vs Mounjaro vs Ozempic
How the three generations of weight loss drugs compare — single, dual, and triple agonists.
Updated February 2026
Tirzepatide vs Semaglutide: Complete Comparison (2026 Data)
Tirzepatide vs semaglutide with SURMOUNT-5 head-to-head data: -20.2% vs -13.7% weight loss. Full comparison of efficacy, side effects, and access.
Updated February 2026
Zepbound vs Wegovy: Which Weight Loss Drug Is Better?
Zepbound produced -20.2% vs Wegovy's -13.7% weight loss in the SURMOUNT-5 head-to-head trial. Full comparison of cost, side effects, and CV data.
Updated February 2026
Mounjaro vs Ozempic: Which Is Better for Weight Loss and Diabetes?
Mounjaro produced twice the weight loss of Ozempic in head-to-head trials. Practical comparison of cost, insurance, and prescribing differences.
Updated February 2026
Retatrutide vs CagriSema (Cagrilintide + Semaglutide): Triple Agonist vs Amylin + GLP-1 Combo
Cagrilintide vs retatrutide: triple agonist vs amylin + GLP-1 combo — 28.7% vs 22.7% weight loss, different receptors, and stacking considerations.
Updated February 2026
GLP-1 guide
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Which GLP-1 Drug Is Best for Weight Loss? (2026 Guide)
Decision framework for choosing the best GLP-1 drug: by max weight loss, CV protection, oral option, diabetes control, or liver fat.
Updated February 2026
GLP-1 Drug Comparison Tool: Compare Weight Loss Drugs Side by Side
Interactive comparison tool for GLP-1 weight loss drugs. Select 2-3 drugs to compare mechanism, efficacy, cost, and status.
Updated February 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
Tirzepatide vs Semaglutide: Complete Comparison (2026 Data)
Tirzepatide vs semaglutide with SURMOUNT-5 head-to-head data: -20.2% vs -13.7% weight loss. Full comparison of efficacy, side effects, and access.
Updated February 2026
Ozempic vs Wegovy: Same Drug, Different Purpose
Ozempic and Wegovy both contain semaglutide. The difference: indication (diabetes vs weight loss), max dose (2.0 vs 2.4 mg), and insurance coverage.
Updated February 2026
Mounjaro vs Ozempic: Which Is Better for Weight Loss and Diabetes?
Mounjaro produced twice the weight loss of Ozempic in head-to-head trials. Practical comparison of cost, insurance, and prescribing differences.
Updated February 2026
Peptides for weight loss
See all →
Peptides for Weight Loss vs GLP-1 Drugs: What the Evidence Says
GLP-1 drugs have Phase 3 trials and FDA approval. Research peptides have failed trials and animal data. The full evidence comparison.
Updated March 2026
Are Peptides Legal in 2026? The FDA Reclassification Explained
The FDA's advisory committee recommended six of seven peptides on July 23-24, 2026 — against its own scientists. Why recommended still is not legal, and what it means for weight loss drugs.
Updated July 2026
Grey Market Retatrutide: Risks, Dangers, and What You Should Know
Grey market retatrutide is unregulated, untested, and potentially dangerous. Here's what the data shows and how to access it safely.
Updated February 2026
Retatrutide vs AOD-9604: Triple Agonist vs Growth Hormone Fragment
Retatrutide produced 28.7% weight loss in Phase 3 trials. AOD-9604 failed its largest trial. Here's how they compare.
Updated March 2026
Safety & side effects
See all →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
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
Weight Loss Drugs and Hair Loss: What Retatrutide's 24% Weight Loss Means
More weight loss means more hair shedding. Retatrutide's 24% weight loss likely puts it at the top — here's the clinical data and what to do about it.
Updated March 2026
Retatrutide and Pregnancy: What Triple Agonism Means for Fertility and Safety
Three receptors, three pregnancy concerns. What GLP-1, GIP, and glucagon receptor research means for retatrutide and reproductive safety.
Updated March 2026
Grey Market Retatrutide: Risks, Dangers, and What You Should Know
Grey market retatrutide is unregulated, untested, and potentially dangerous. Here's what the data shows and how to access it safely.
Updated February 2026
GLP-1 Drugs and Mental Health: What the Evidence Actually Shows
The FDA cleared GLP-1 drugs of psychiatric risk after reviewing 91 trials. The surprising finding: these drugs may actually improve depression.
Updated June 2026
Clinical data & FDA
See all →
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
Retatrutide Results: Before and After — What the Data Actually Shows
No real before/after photos exist. Here's what the clinical trial data shows: 28.7% average weight loss at 68 weeks, month-by-month breakdown.
Updated February 2026
How to Sign Up for a Retatrutide Clinical Trial
Numbered TRIUMPH obesity trials are closed; open options include TRIUMPH-7 (low back pain) and the MASLD master protocol. How to find and enroll.
Updated July 25, 2026
Other weight loss drugs
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What Is Cagrilintide? The Amylin Analog Behind CagriSema
Novo Nordisk's long-acting amylin analog — 11.5% weight loss as monotherapy, and the key ingredient in CagriSema.
Updated February 2026
What Is CagriSema? Novo Nordisk's Amylin + GLP-1 Weight Loss Combination
Novo Nordisk's amylin + GLP-1 combination — 20.4% weight loss in REDEFINE 1, NDA filed December 2025.
Updated February 2026
What Is Foundayo (Orforglipron)? Lilly's FDA-Approved Oral GLP-1 Weight Loss Pill
Eli Lilly's FDA-approved oral GLP-1 pill — 12.4% weight loss, no injections, no fasting. Starting at $149/month.
Updated April 2026
What Is Survodutide? The Dual GLP-1/Glucagon Agonist for Weight Loss and MASH
Boehringer Ingelheim's dual GLP-1/glucagon agonist — 18.7% weight loss in Phase 2, 83% MASH resolution, Phase 3 ongoing.
Updated February 2026
What Is Mazdutide (Xinermei)? The First GLP-1/Glucagon Drug Approved in China
The first GLP-1/glucagon dual agonist approved anywhere — how it works, what the trials show, and why it matters for the obesity drug landscape.
Updated February 2026
What Is Amycretin? Novo Nordisk's Oral GLP-1/Amylin Weight Loss Drug
Novo Nordisk's first-in-class GLP-1/amylin dual agonist — 13.1% weight loss as a daily pill in 12 weeks, 22% as a weekly injection in 36 weeks.
Updated March 2026
Fact-checking viral videos
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Andrew Huberman on Retatrutide: What He Said and What the Data Shows
Huberman called retatrutide 'the peptide that changes everything.' Here's what he said and what the data actually shows.
Updated June 2026
Pathologist Dr. Amin Hedayat on Retatrutide: What He Said and What the Data Shows
A pathologist dismantles retatrutide piece by piece — mechanism, liver data, heart risks, and anhedonia fact-checked.
Updated April 2026
Dr. Dan on Retatrutide vs Ozempic: Obesity Expert Fact Check
Obesity expert Dr. Dan's retatrutide vs Ozempic comparison — Phase 2 data, side effects, and timeline predictions fact-checked.
Updated February 2026
JD Denham on Retatrutide: Triple Agonist Mechanism, Dosing, and Fat Loss Claims — Fact Check
Peptide of the Week hosts on retatrutide dosing, nausea, muscle loss, and fat burning — fact-checked against clinical data.
Updated February 2026
GLP-3 Wiki is an independent informational resource. We are not affiliated with Eli Lilly, Novo Nordisk, or any pharmaceutical company. Retatrutide is an investigational drug that has not been approved by the FDA. This site is not medical advice. Always consult a healthcare provider before making decisions about medication.