GLP-1 / incretin
Retatrutide
Phase 3 complete; not approvedLarge human trialsRetaLY3437943Triple G
A once-weekly injectable from Eli Lilly that acts on three gut-hormone receptors (GLP-1, GIP and glucagon). In phase 3 trials it produced the largest average weight loss of any obesity drug so far. It isn't approved anywhere yet, so anything sold now is unregulated.
- Canada
- Not authorized
- United States
- Not approved; Lilly plans to file in Q1 2027
Download profile Opens in Vialchemy on your iPhone, where it's added to your Library as your own.
Not medical advice — talk to your doctor before making medical decisions.
At a glance
- Class
- GLP-1 / GIP / glucagon agonist
- Mechanism
- Lowers appetite and slows stomach emptying (GLP-1, GIP) and raises energy use and liver fat burning (glucagon)
- Evidence
- Late-stage human trials
- Canada
- Not authorized
- Us
- Not approved; filing planned Q1 2027
- Half Life
- About 6 days
- Routes
- SubQ, weekly
- Common Side Effects
- Diarrhea, nausea, constipation, vomiting, less appetite, higher heart rate
- Key Cautions
- Unregulated supply; heart rate; GI tolerability at higher doses
- Trial Weight Loss
- Up to ~28% at 80 weeks (TRIUMPH-1, top dose)
What the research says
Is it approved?
No. Phase 3 trials (TRIUMPH) reported in 2025-2026 and Lilly plans to file with the FDA in Q1 2027. Health Canada named retatrutide in its April 2026 warning about unauthorized injectable peptides.
How much weight did people lose in trials?
TRIUMPH-1 (obesity, no diabetes): about 28% at the top dose over 80 weeks vs about 2% on placebo. With type 2 diabetes (TRIUMPH-2): up to about 21%. Trials raised the dose in steps over months.
Does it raise heart rate?
Yes, resting heart rate rose a few beats per minute on average in trials. Tracking resting HR in the app is a good idea; a big or sustained jump is worth raising with a doctor.
Combine with another GLP-1 (semaglutide, tirzepatide)?
No. They act on the same receptors, so stacking them adds side effects without trial evidence of extra benefit.
Combine with tirzepatide?
No, same reason: overlapping GLP-1/GIP action.
With GH-raising peptides (CJC-1295, ipamorelin, tesamorelin)?
No trial data. GH raises blood sugar while retatrutide lowers it, and both can affect heart rate and fluid. Track glucose and resting HR if a prescriber is involved.
Phase 3 results so far
| Trial | Who | Result |
|---|---|---|
| TRIUMPH-4 (Dec 2025) | Obesity with knee osteoarthritis | Large weight loss and less knee pain |
| TRIUMPH-1 (May 2026) | Obesity or overweight, no diabetes | Up to ~28% weight loss at 80 weeks vs ~2% placebo |
| TRIUMPH-2 (Jul 2026) | Obesity with type 2 diabetes | Up to ~21% weight loss; A1C down 1.4-1.6 points |
| TRIUMPH-3 (Jul 2026) | BMI 35+ with heart disease | Up to ~23% weight loss; heart outcomes not clearly different from placebo |
Numbers are Lilly's efficacy estimates (people who stayed on treatment). Stopping because of side effects was 4-14% depending on dose and trial, vs about 5% on placebo.
Common side effects and cautions
- Nausea, diarrhea, constipation, vomiting and reflux are the most common, mostly in the first weeks and after each dose increase.
- Eating much less can mean losing muscle along with fat. Protein and strength training help protect it.
- Gallstones are more likely with fast weight loss.
- Slowed stomach emptying can change how oral medicines absorb, and matters before surgery or sedation. Tell the anesthetist you're on it.
- If you take insulin or a sulfonylurea, the risk of low blood sugar goes up.
- Not for use in pregnancy or with a personal or family history of medullary thyroid cancer or MEN2 (label warning for this class).
Get medical care if
- Redness, heat, swelling or pus at a site that spreads or comes with fever
- Hives, swelling of the face or throat, or trouble breathing (call 911)
- Severe stomach pain that won't go away, with or without vomiting (possible pancreatitis)
- Pain in the upper right belly, fever or yellow skin or eyes (possible gallbladder problem)
- Can't keep fluids down, very dark urine or dizziness when standing (dehydration, which can affect the kidneys)
- A lump or swelling in the neck, trouble swallowing or a hoarse voice that won't go away
Buying and quality
- Not authorized by Health Canada. Products sold online as "research use only" are illegal to sell for human use in Canada, and the label doesn't change that.
- Health Canada warns these products may contain too much, too little or none of the peptide, plus contaminants like endotoxins, solvents, heavy metals or bacteria.
- A certificate of analysis (COA) from the seller isn't independent proof. A 98% purity result still leaves 2% unidentified.
- If you use it anyway: one clean needle per injection, sterile technique, label and date every vial, and stop if a site gets hot, red and spreading.
Dose calculator
Doses are set with your prescriber. This converts a dose you already have into what to draw; it doesn't recommend one. Check every number against your syringe and your vial's label.
Doses left in the vial
A blend vial
Not medical advice — talk to your doctor before making medical decisions.
Sources
Researched 2026-10-27. Trial results and approval status change.
General education, not medical advice. Nothing here is a dose recommendation. Doses, schedules and changes are set with a prescriber.