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Research Documentation 3 min read16 October 2026

Retatrutide Side Effects: What Published Trials Report

Which adverse events were reported in published retatrutide trials, how often, and what those trials can and cannot tell you.

The short answer

In published trials, the most common retatrutide side effects were gastrointestinal, such as nausea and diarrhoea, and they were more frequent in the higher dose groups. Dysaesthesia (altered skin sensation), low blood pressure and a temporary rise in heart rate were also reported more often than with placebo.

These are findings for the sponsor's investigational product, given under medical supervision to selected patients. They are not a safety profile for research-grade material, and this page is not medical advice.

What the trials reported

TRIUMPH-2, phase 3

1,152 adults with obesity and type 2 diabetes, followed for 80 weeks (Lancet, 2026). The ranges below span the three retatrutide dose groups.

EventRetatrutide groupsPlacebo
Diarrhoea27-34%13%
Nausea14-28%8%
Dysaesthesia4-7%1%
Hypotension1-6%under 1%
Stopped treatment permanently (adverse event or death)4-12%5%

Nausea rose from the lowest to the highest dose group. Investigators judged all reported deaths unrelated to the study drug.

Other published trials

  • •Phase 2 (NEJM, 2023; 338 adults, 48 weeks). Gastrointestinal events were the most common, were dose-related and were mostly mild to moderate. Heart rate rose in a dose-dependent way, peaked at 24 weeks and then declined.
  • •TRIUMPH-1, phase 3 (NEJM, 2026; 2,339 adults, 80 weeks). The most common adverse events were again gastrointestinal.

What is not known

  • •Long-term effects. The longest published trials ran 80 weeks. There are no multi-year safety data.
  • •Rare events. Trials of this size cannot reliably estimate uncommon outcomes. For the wider drug class, a 2026 review reports a probable association with gallstones and no excess of pancreatitis in randomised trials, and describes retatrutide-specific data as limited.
  • •Real-world populations. Trial participants were screened and monitored. People outside a trial differ.

Why trial data do not describe research-grade material

  • •Different product. The trial product was made and controlled to clinical standards under a protocol. A research vial was not.
  • •A certificate is not a safety assessment. A batch certificate reports identity and purity. It does not establish sterility, endotoxin levels or suitability for any use in people. See reading a peptide COA and understanding HPLC purity.
  • •Anecdote is not data. Forum and social-media reports are uncontrolled and cannot show how often an effect occurs or whether the material caused it.

Anyone who is unwell after using an unlicensed product should seek medical advice.

Related pages

The retatrutide identity page covers what the molecule is and where its development stands. The comparison with tirzepatide and semaglutide sets out the receptor differences, and the retatrutide buying guide covers the catalogue side. Published batch reports are in the COA library.

Key references

  • •Bellido V, le Roux CW, Ekinci EI, et al. Retatrutide in adults with obesity and type 2 diabetes (TRIUMPH-2): a double-blind, parallel-group, randomised, placebo-controlled, phase 3 trial. Lancet. 2026;408(10563):1455-1472. doi:10.1016/S0140-6736(26)01861-1
  • •Jastreboff AM, Kaplan LM, Davies MJ, et al. Retatrutide, a triple hormone receptor agonist, for treatment of obesity (TRIUMPH-1). N Engl J Med. 2026. doi:10.1056/NEJMoa2604169
  • •Jastreboff AM, Kaplan LM, Frías JP, et al. Triple-hormone-receptor agonist retatrutide for obesity: a phase 2 trial. N Engl J Med. 2023;389(6):514-526. doi:10.1056/NEJMoa2301972
  • •Singhani V, Ehsan M, Valencia S, et al. Gastrointestinal adverse effects of GLP-1 receptor agonists and dual GIP/GLP-1 receptor agonists: a narrative expert review. Nutr Clin Pract. 2026;41(5):1318-1333. doi:10.1002/ncp.70180

Scope and laboratory-use boundary

Materials sold on this site are supplied solely for non-clinical in-vitro laboratory research. They must not be ingested, injected, inhaled, applied or otherwise administered to a human or animal.

We do not provide dosing, routes of administration, treatment guidance, cosmetic-use guidance or in-vivo protocols. Preparation, storage and handling must follow a validated institutional SOP, the material documentation and an appropriate risk assessment.

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Site materials are supplied solely for non-clinical in-vitro laboratory research. They must not be used in or on humans or animals. We do not provide dosing, routes of administration, treatment, cosmetic-use or in-vivo guidance. Read the legal and research-use terms.