Retatrutide Side Effects: What Studies and Users Report
What FDA labels and clinical studies report for Retatrutide, how strong that evidence is, and what is still unknown.
Medically reviewed by Juan Pablo Frías, MD · · DisclosureGLP-1 / GIP / glucagon triple agonistUpdated
Side effects reported in studies
Side effects reported in published studies, strongest design first. Frequencies are quoted as the source gives them; animal results are labelled.
| Side effect | How common | Study type | Source |
|---|---|---|---|
| Gastrointestinal events | most common | Human RCTn = 2339 | The New England journal of medicine 2026, PMID 42814954 |
| Diarrhoea | 96 [34%] of 286 on 12 mg vs 38 [13%] of 287 on placebo | Human RCTn = 1152 | Lancet 2026, PMID 42810372 |
| Nausea | 40 [14%], 59 [21%], 80 [28%] (4, 9, 12 mg) vs 23 [8%] placebo | Human RCTn = 1152 | Lancet 2026, PMID 42810372 |
| Discontinuation due to adverse events or death | 9 mg 33 [12%], 12 mg 22 [8%], 4 mg 11 [4%], placebo 14 [5%] | Human RCTn = 1152 | Lancet 2026, PMID 42810372 |
| Discontinuation due to adverse events | 2-5% with retatrutide vs 0% with placebo | Human RCTn = 537 | Lancet 2026, PMID 42250575 |
| Serious adverse events“Adverse events were similar between groups.” | Frequency not stated | Human RCTn = 189 | The lancet. Diabetes & endocrinology 2025, PMID 40609566 |
| Gastrointestinal events | most common; dose-related | Human RCTn = 338 | The New England journal of medicine 2023, PMID 37366315 |
| Heart rate increase | dose-dependent, peaked at 24 weeks | Human RCTn = 338 | The New England journal of medicine 2023, PMID 37366315 |
| Gastrointestinal events | 67 (35%) of 190 on retatrutide vs 6 (13%) of 45 on placebo | Human RCTn = 281 | Lancet 2023, PMID 37385280 |
| Severe hypoglycaemia“There were no reports of severe hypoglycaemia and no deaths during the study.” | Frequency not stated | Human RCTn = 281 | Lancet 2023, PMID 37385280 |
| Treatment-emergent adverse events | 33 (63%) on LY3437943 vs 8 (54%) on placebo | Human RCTn = 72 | Lancet 2022, PMID 36354040 |
| Overall adverse-event risk | highest risk of the compared drugs | Meta-analysisn = 29506 | Obesity 2025, PMID 40685589 |
Stomach and gut side effects rose with dose, were mostly mild to moderate, and were partly reduced by a 2 mg rather than 4 mg starting dose.
- Nausea
- Decreased appetite
- Diarrhea
- Vomiting
- Constipation
- Raised heart rate at higher doses
Source: phase 2 trial (New England Journal of Medicine, 2023). Rates by dose are pending review.
What is not known
- How common each effect is at the doses people use outside of studies.
- Effects that take longer to appear than the length of the published studies.
- How Retatrutide interacts with other medicines and supplements.
- Whether research-grade products, which are not checked by the FDA, behave like the material used in studies.
When to get medical help
Get urgent care for: trouble breathing, swelling of the face or throat, a widespread rash, severe or lasting stomach pain, fainting, or an injection site that becomes hot, red and spreading.
This is not a complete list. A doctor or pharmacist can help you judge whether a symptom is related.
Common questions
What are the side effects of Retatrutide?
In the phase 2 trial the most common were nausea, decreased appetite, diarrhea. Stomach and gut side effects rose with dose, were mostly mild to moderate, and were partly reduced by a 2 mg rather than 4 mg starting dose. Higher doses also raised heart rate.
Is Retatrutide safe?
Its safety has not been established by an FDA review. Retatrutide is investigational and not approved for any use. Research-chemical products are not checked for purity or dose.
Is Retatrutide banned in sport?
Yes. Prohibited by WADA (S0). Tested athletes should not use it.
More on Retatrutide
DosageDoses used in published trials, the titration pattern and a units chart.CalculatorVial, water and dose to syringe units.ResultsStudy outcomes and when they were measured.PricePrice per mg and per week from dated listings. No vendor links.Legal statusFDA, compounding and WADA status with dates.How to injectSites, syringe types and hygiene, step by step.
Sources
- 1Triple-Hormone-Receptor Agonist Retatrutide for Obesity: A Phase 2 Trial (Jastreboff AM et al.)New England Journal of Medicine · 2023PMID 37366315Accessed 2 Oct 2026
- 2A Phase 2 Study of Once-Weekly LY3437943 Compared With Placebo in Participants Who Have Obesity or Are Overweight With Weight-Related Comorbidities (NCT04881760; arms and posted results)ClinicalTrials.gov (U.S. National Library of Medicine) · 2021clinicaltrials.govAccessed 2 Oct 2026
- 3Retatrutide, a Triple Hormone Receptor Agonist, for Treatment of Obesity (TRIUMPH-1; Jastreboff AM et al.)New England Journal of Medicine · 2026PMID 42814954Accessed 2 Oct 2026
- 4Retatrutide in adults with obesity and type 2 diabetes (TRIUMPH-2): a double-blind, parallel-group, randomised, placebo-controlled, phase 3 trial.Lancet (London, England) · 2026PMID 42810372Accessed 2 Oct 2026
- 5Efficacy and safety of retatrutide, a GIP, GLP-1, and glucagon receptor agonist, in people with type 2 diabetes and inadequate glycaemic control with diet and exercise (TRANSCEND-T2D-1): a double-blind, randomised, phase 3 trial.Lancet (London, England) · 2026PMID 42250575Accessed 2 Oct 2026
- 6Effects of retatrutide on body composition in people with type 2 diabetes: a substudy of a phase 2, double-blind, parallel-group, placebo-controlled, randomised trial.The lancet. Diabetes & endocrinology · 2025PMID 40609566Accessed 2 Oct 2026
- 7Retatrutide, a GIP, GLP-1 and glucagon receptor agonist, for people with type 2 diabetes: a randomised, double-blind, placebo and active-controlled, parallel-group, phase 2 trial conducted in the USA.Lancet (London, England) · 2023PMID 37385280Accessed 2 Oct 2026
- 8LY3437943, a novel triple GIP, GLP-1, and glucagon receptor agonist in people with type 2 diabetes: a phase 1b, multicentre, double-blind, placebo-controlled, randomised, multiple-ascending dose trial.Lancet (London, England) · 2022PMID 36354040Accessed 2 Oct 2026
- 9Efficacy and Safety of GLP-1 Receptor Agonists, Dual Agonists, and Retatrutide for Weight Loss in Adults With Overweight or Obesity: A Bayesian NMA.Obesity (Silver Spring, Md.) · 2025PMID 40685589Accessed 2 Oct 2026
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