What are the side effects of retatrutide?
FAQGastrointestinal effects dominate, as they do across the incretin class, and they were most pronounced during dose escalation. One finding is specific to retatrutide: dysesthesia — abnormal skin sensations — was reported in about 21% of participants at 12 mg in TRIUMPH-4, and has not been reported with semaglutide or tirzepatide.
The dysesthesia finding
Dysesthesia covers tingling, burning or prickling sensations in the skin. It is the one effect that separates retatrutide’s reported profile from the rest of the class, and the proposed explanation is the glucagon-receptor arm that the other two compounds do not have. That explanation is a hypothesis about mechanism rather than a demonstrated cause.
Reported rates
| Effect | Reported rate | Reported in |
|---|---|---|
| Nausea | up to 60% | Phase 2, 12 mg |
| Diarrhoea | 15–33% | higher doses |
| Vomiting | 21–26% | higher doses |
| Constipation | 11–25% | across doses |
| Dysesthesia | ~21% | TRIUMPH-4, 12 mg |
| Injection-site reactions | up to 8% | across doses |
| Heart-rhythm changes | ~6% (vs 3% placebo) | trials |
| Gallbladder events | ~1.1% | trials |
| Liver-enzyme elevation (transient ALT) | ~1% | trials |
| Pancreatitis | ~0.4% | Phase 2 |
Resting heart rate rose by an average of 5–10 beats per minute, peaking around week 24 before declining. Every figure here is an observed rate in a controlled trial population, not a prediction for any individual.
How the totals compare
Discontinuation attributable to side effects ranged from 6% to 16% across the Phase 2 trials, concentrated in the escalation phase rather than at maintenance. The serious adverse event rate was 4% — the same figure recorded in the placebo arm, which is the comparison that gives the number meaning. Most reported effects were graded mild to moderate and diminished with continued administration.
What this data does not cover
Every rate above comes from a controlled trial of Lilly’s clinical material, administered at defined doses under supervision, with adverse events collected systematically. A vial sold on the research market is not that material, and the trial safety profile does not transfer to it: identity, purity and actual content are separate questions from pharmacology, and no rate table can speak to them.
The programme is also ongoing. The longest published exposure is 68 weeks, so effects that would only appear over years are outside what any current dataset could have detected.
For other common questions regarding retatrutide, see the full Retatrutide profile.
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