Retatrutide
EXTENSIVELY STUDIEDTriple GLP-1/GIP/glucagon receptor agonist | Weight loss & diabetes
Updated: August 2026 · Based on the phase III trials TRIUMPH-1 and TRANSCEND-T2D-1 (2026).
Key points
- What it is: triple agonist of the GLP-1 / GIP / glucagon receptors (LY3437943), developed by Eli Lilly.
- Main use: weight loss (the highest documented in a phase III trial) and type 2 diabetes.
- Typical dose: 0.5–12 mg, once a week, subcutaneous injection, with gradual escalation every 4 weeks.
- Key result: −28.3% body weight at 80 weeks (12 mg); up to −30.3% at 104 weeks (TRIUMPH-1).
- Common effects: nausea and diarrhea (dose-dependent); dysesthesia reported in the trials.
- Comparison: more potent than tirzepatide (dual) and semaglutide (mono).
- Status: investigational, not FDA-approved (approval expected around late 2027).
Overview
What is Retatrutide?
Retatrutide (LY3437943) is a novel triple agonist of the GLP-1, GIP and glucagon receptors, in advanced research for weight management and diabetes. The pivotal Phase III TRIUMPH-1 trial (May 2026) achieved 28.3% weight loss at 80 weeks on 12 mg, with a 104-week extension cohort reaching 30.3%. FDA approval is realistically expected by late 2027.
Key benefits
Triple hormone receptor activation provides superior weight loss (24.2%), better glycemic control and greater cardiovascular benefits compared with single or dual agonists.
Mechanism of action
It activates three receptors at once: GLP-1 to suppress appetite, GIP for insulin sensitivity and glucagon to increase energy expenditure and hepatic fat oxidation.
Quick start guide
Dosing protocol (weekly titration)
| Phase | Weeks | Weekly dose | Goal |
|---|---|---|---|
| Start | 1–4 | 0.5–2 mg | Adaptation; minimizes nausea and diarrhea |
| Titration 1 | 5–8 | 4 mg | First gradual increase |
| Titration 2 | 9–12 | 6 mg | Progressive increase |
| Titration 3 | 13–16 | 9 mg | Approaching target dose |
| Maintenance | 17+ | 12 mg (max.) | Maximum dose in the TRIUMPH-1 trial |
Subcutaneous route (abdomen, thigh or arm), once a week on the same day, rotating the site. The dose is increased every 4 weeks. Investigational compound: the exact dose must be set by a healthcare professional.
🧮 Calculate your exact syringe dose →Retatrutide vs Tirzepatide vs Semaglutide
| Semaglutide | Tirzepatide | Retatrutide | |
|---|---|---|---|
| Receptors | GLP-1 | GLP-1 + GIP | GLP-1 + GIP + glucagon |
| Type | Mono | Dual | Triple |
| Weight loss (max. in trials) | ~15% | ~21–22% | ~24–28% |
| Frequency | 1×/week | 1×/week | 1×/week |
| FDA status | Approved | Approved | Investigational |
⚠️ Who should NOT use it
- Personal or family history of medullary thyroid carcinoma or MEN 2 syndrome.
- History of pancreatitis.
- Pregnancy or breastfeeding, or if planning a pregnancy.
- Always under the supervision of a healthcare professional.
What to expect
- Week 1-2: initial appetite suppression and mild gastrointestinal effects as the body adapts to triple hormone activation.
- Week 2-4: noticeable reduction in cravings and portion sizes, early weight loss (2-5%).
- Week 4-8: significant appetite control and steady weight loss (5-10%), improved glucose control in people with diabetes.
- Week 8-16: substantial weight reduction (10-18%) with enhanced energy expenditure and metabolic improvements.
- Week 16-24: major weight-loss milestone (15-22%) with cardiovascular benefits and liver fat reduction.
- Week 24-48: maximum clinical efficacy (20-24.2%) with comprehensive metabolic improvements and sustained benefits.
Side effects & safety
- The most common side effects are gastrointestinal (nausea 43%, diarrhea 33% at 12 mg), usually mild to moderate and dose-dependent.
- Dysesthesia (abnormal touch sensations) confirmed across two Phase III trials, reproducible between studies, suggesting a class-level effect requiring labeling attention.
- A conservative start at 0.5 mg weekly minimizes gastrointestinal side effects (13% vs 73-94% at higher doses) — increase gradually every 4 weeks.
- Phase III discontinuation rates due to adverse events ranged from about 4% to 18%, depending on dose and population.
- Watch for signs of pancreatitis (severe abdominal pain radiating to the back) — discontinue immediately if suspected.
- Heart rate increases are common, especially in the first 24 weeks — monitor cardiovascular status regularly.
- Contraindicated in patients with a personal or family history of medullary thyroid carcinoma or MEN 2 syndrome.
- May cause rapid weight loss — some discontinuations are due to perceived excessive weight loss.
- Severe allergic reaction: rash, itching, swelling of the face, lips or throat, or difficulty breathing.
- Severe, persistent abdominal pain radiating to the back (possible pancreatitis) — stop immediately.
- Racing heartbeat or persistent palpitations.
- Lump or swelling in the neck, hoarseness or difficulty swallowing.
- Persistent vomiting or diarrhea with signs of dehydration.
- Excessive or overly rapid weight loss.
Frequently asked questions
What is Retatrutide?
Retatrutide (LY3437943) is a triple agonist of the GLP-1, GIP and glucagon receptors, in advanced research for weight management and diabetes.
What is Retatrutide researched for?
It is studied mainly for weight loss, with very high results in clinical trials, and for glucose control.
How does Retatrutide work?
It activates three receptors at once: GLP-1 to suppress appetite, GIP for insulin sensitivity and glucagon to increase energy expenditure.
How long does Retatrutide take to work?
In studies, appetite suppression appears within the first 24-48 hours and weight loss is progressive over the weeks.
What is the usual Retatrutide dose?
In trials, increasing doses up to 8-12 mg weekly were used, starting very low to minimize side effects.
How is Retatrutide administered?
By subcutaneous injection once a week, rotating the site.
How much weight can you lose with Retatrutide?
In the TRIUMPH-1 trial, around 24-28% weight loss was reached, one of the highest figures described to date.
How is Retatrutide stored?
The lyophilized powder at room temperature and the reconstituted solution refrigerated. See the storage guide.
What are the side effects of Retatrutide?
Mainly digestive (nausea, diarrhea), dose-dependent, and dysesthesia (abnormal touch sensations) has been described in some cases.
What is the difference between Retatrutide, Semaglutide and Tirzepatide?
Retatrutide acts on three receptors, tirzepatide on two and semaglutide on one; the triple action is associated with the greatest weight loss.
Is Retatrutide approved?
Not yet. It is in advanced clinical trials; FDA approval is realistically expected by late 2027.
Research areas
- Weight loss
- Type 2 diabetes control
- Appetite reduction
- Energy expenditure and metabolism
- Cardiovascular health
Related peptides
- Semaglutide — GLP-1 receptor agonist, approved for weight and diabetes.
- Tirzepatide — Dual GIP/GLP-1 agonist, approved for weight and diabetes.
- Tesamorelin — GHRH analog researched for visceral fat.
Related articles
Related topics
- Retatrutide for weight loss
- Retatrutide and diabetes
- Retatrutide dose
- Retatrutide side effects
- Retatrutide vs Tirzepatide
- Retatrutide triple agonist
Summary
What it is: Triple agonist of the GLP-1, GIP and glucagon receptors (LY3437943).
How it is researched: Weekly subcutaneous injection; increasing doses up to 8-12 mg.
Key features: Triple action; weight loss up to 24-28% in trials. Not yet FDA-approved.
Related peptides: Semaglutide, Tirzepatide and Tesamorelin.