Retatrutide
Eli Lilly's investigational triple-hormone agonist: GIP, GLP-1 and glucagon in one weekly shot.
Overview
Retatrutide is a once-weekly injectable from Eli Lilly that acts on three hormone receptors at once. In its phase 2 trial it produced the largest average weight loss seen in a drug trial at the time, and phase 3 results reported in 2026 were also strongly positive. It is still investigational: no country has approved it, and Lilly has said it plans to file with the FDA around early 2027.
How it works
A 39-amino-acid peptide with a C20 fatty-acid chain that binds albumin, giving it a long half-life. It activates GIP and GLP-1 receptors (appetite, insulin release, slower stomach emptying) like tirzepatide, and adds glucagon-receptor activity, which is thought to raise energy use and reduce liver fat.
Evidence
4/5
Large phase 2 RCT (NEJM 2023) and multiple positive phase 3 trials (TRIUMPH program). Not yet approved, and long-term safety data is still being collected.
Half-life
About 6 days (once-weekly dosing)
Known as
LY3437943, AMP-3 (RT), GGG tri-agonist, "Reta"
Compound facts
- Type
- Synthetic peptide
- CAS Number
- 2381089-83-2
- Molecular Weight
- 4,731 g/mol
- Amino Acids
- 39
- Fatty Acid Chain
- C20 diacid
Reported benefits
Large weight loss
Phase 2: average −24.2% body weight at 48 weeks on 12 mg vs −2.1% on placebo.
Weight loss with type 2 diabetes
Phase 3 TRIUMPH-2: up to about −20.8% at 80 weeks, with A1c down by up to 1.6 points.
Cardiometabolic markers
Phase 3 trials reported better triglycerides, blood pressure, waist size and CRP.
Liver fat reduction
Substantial falls in liver fat seen in a phase 2 sub-study; glucagon activity is the proposed reason.
“Anecdotal” means reported by users, not shown in controlled trials.
Community-reported regimens
Not recommendations. These are commonly cited ranges, shown so you can see what real-world use looks like.
| Plan | Dose | Frequency | Duration | Route |
|---|---|---|---|---|
| Trial-style titration (start) Phase 2 started most groups at 2 mg and stepped up every 4 weeks (2 → 4 → 8 → 12 mg). A lower start reduced GI side effects. | 2000 mcg | Once weekly | 4 weeks, then step up | Subcutaneous |
| Community-reported low start Some users start at 500 mcg–1 mg to test tolerance. Not a studied dose. | 1000 mcg | Once weekly | 4 weeks, then reassess | Subcutaneous |
| Trial maintenance (top dose) 12 mg was the highest phase 2 dose. Reached only after months of stepwise titration. | 12000 mcg | Once weekly | Trials ran 48–80 weeks | Subcutaneous |
Reconstitution calculator
Set up for Retatrutide. Switch peptide or vial size any time.
1Mix
Add 2 mL water for 5 mg/mL
2Draw
Draw to 40 units = 0.4 mL = 2 mg
Drag the plunger to set your dose.
3Inject
Next site
Right belly, upper
Tap a site after you inject to keep a rotation.
Pinch the skin, stay 2 in. from the navel, then into a sharps bin.
- Doses per vial
- 5
- Vial lasts
- 35 days
- Good once mixed
- ~28 days
- Syringe
- 50-unit, 0.5 mL
The vial outlasts its ~28-day shelf life once mixed. A smaller vial wastes less.
Math only: concentration (mg/mL) = vial mg ÷ mL of water; units = dose (mg) ÷ concentration × 100. Always double-check against your own vial label and a clinician. This tool does not recommend a dose.
Reconstitution
Diluent: Bacteriostatic water (0.9% benzyl alcohol) — allows multiple draws from one vial.
- Wipe both vial tops with an alcohol swab and let dry.
- Draw the diluent, then inject it slowly down the inside wall of the vial — never straight onto the powder.
- Swirl gently or let it sit; do not shake. Foam can damage peptides.
- Solution should be clear. Cloudy, stringy or discolored = discard.
- Doses change as you titrate, so re-check units each time you step up.
- Common mix: 10 mg + 2 mL = 5 mg/mL (2 mg = 40 units).
Storage
Powder
Freezer / fridge
Keep sealed vial in the freezer (−20 °C) for long-term storage; fridge (2–8 °C) is fine for a few weeks. Keep dry and out of light.
After mixing
~28 days
Refrigerate at 2–8 °C. Never freeze after mixing. Keep upright, capped, and out of light.
Travel
Keep cool
Short trips at room temperature are generally fine for powder; keep mixed vials cold.
- A weekly drug means one vial lasts many weeks; consider mixing a smaller volume or a smaller vial so you use it within about 4 weeks.
Side effects & cautions
Reported side effects
- Nausea, diarrhea, constipation, vomiting (most common, dose-related)
- Reduced appetite
- Raised resting heart rate (seen in trials, dose-related)
- Skin tingling or sensitivity (dysesthesia) reported in some trial participants
- Injection-site reactions
Cautions
- Boxed warning class: GLP-1 drugs caused thyroid C-cell tumors in rodents. Do not use with a personal or family history of medullary thyroid cancer or MEN2.
- Pancreatitis has been reported. Severe, persistent belly pain that may spread to the back needs urgent care.
- Gallbladder problems (gallstones) are more common, especially with fast weight loss.
- Do not combine with another GLP-1 drug (semaglutide, tirzepatide, retatrutide, etc.).
- Raises low-blood-sugar risk when combined with insulin or sulfonylureas.
- Not for use in pregnancy; stop well before trying to conceive. Slowed stomach emptying can matter before surgery or sedation.
- Investigational: long-term safety is not established, and research-grade product is not the drug used in trials.
FDA & international status
Not FDA-approved (phase 3)
Investigational drug from Eli Lilly. Phase 3 TRIUMPH trials reported positive results in 2025–2026; Lilly has said it plans to submit for FDA approval around early 2027. It cannot legally be compounded, and products sold as 'retatrutide' online are unregulated research chemicals.
Regulations change often — verify with the FDA, EMA, MHRA, Health Canada, TGA and WADA before acting.
Where to buy
Retatrutide vials
Shop this product ↗| Size | Price | Per mg | Stock | Latest COA |
|---|---|---|---|---|
| 10 mg | $69.99 | $7.00 | In stockBuy ↗ | 99.92% pure, lot RT0004 ILS Labs, tested 2026-08-21 |
| 20 mg | $134.99 | $6.75 | In stockBuy ↗ | 99.93% pure, lot RT0005 ILS Labs, tested 2026-07-30 |
| 30 mg | $199.99 | $6.67 | In stockBuy ↗ | 99.57% pure, lot RT0006 ILS Labs, tested 2026-07-30 |
Past COAs (10 lab reports)
- 2026-08-21, 10 mg, lot RT0004, 99.92% pure, measured 10.27mgILS Labs, passedView PDF
- 2026-08-21, 10 mg, lot RT0004, 99.92% pure, measured 10.53mgILS Labs, passedView PDF
- 2026-07-30, 10 mg, lot RT0004, 99.86% pure, measured 10.4mgILS Labs, passedView PDF
- 2026-07-30, 20 mg, lot RT0005, 99.93% pure, measured 21.27mgILS Labs, passedView PDF
- 2026-07-30, 30 mg, lot RT0006, 99.57% pure, measured 31.49mgILS Labs, passedView PDF
- 2026-05-29, 10 mg, lot RT0001, 99.85% pure, measured 10.27mgILS Labs, passedView PDF
- 2026-05-29, 20 mg, lot RT0002, 99.65% pure, measured 20.64mgILS Labs, passedView PDF
- 2026-05-29, 30 mg, lot RT0003, 99.77% pure, measured 31.81mgILS Labs, passedView PDF
- 2026-02-04, 10 mg, lot A1115, 99.794% pure, measured 10.14mgLab not statedView PDF
- 2026-02-04, 20 mg, lot A0112, 99.929% pure, measured 22.56mgLab not statedView PDF
Amino Club list prices as of 2026-10-07, before promo codes. Multi-buy: 2+ units 5% off, 3+ units 7.5% off, 10+ units 40% off. Prices change; confirm on the product page. Mixing? Their bacteriostatic water is Amino H2O from $19.99.
Retatrutide at Amino Club
Check sizes, current price and the certificate of analysis (COA) on the product page. Sold for in-vitro research only.
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- Look for a batch-specific COA with HPLC purity (≥98%) and mass-spec identity.
- Typical vial sizes: 10, 20, 30 mg.
FAQ
Is retatrutide stronger than tirzepatide?
Trial weight loss has been larger than tirzepatide's, but there is no published head-to-head trial yet. Side effects also scale with dose.
Why does the dose go up slowly?
Stepping up every 4 weeks lets your gut adjust. In the phase 2 trial a 2 mg start caused fewer GI side effects than a 4 mg start.
Can I take it with semaglutide or tirzepatide?
No. It already covers the GLP-1 receptor (and GIP). Stacking incretin drugs adds side-effect risk with no studied benefit.