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InvestigationalInvestigational

Retatrutide

The most-searched research peptide on Bing. Investigational only, in late-stage trials, and not approved anywhere in the world (ArentFox Schiff).

Part 1Header & identifiers

Also known as: Investigational triple-agonist (Eli Lilly). Class: GLP-1 / metabolic.

Class
Triple agonist of the GIP, GLP-1 and glucagon receptors
Code name
LY3437943
Route studied
Once-weekly subcutaneous injection
Developer
Eli Lilly

Last reviewed 3 Nov 2026 by The Peptide Informative editorial team. Found an error? Tell us; see our corrections policy.

Part 2Status at a glance

FDANot approved anywhere in the world. Investigational only [3].
Enforcement newsNamed in 2026 FDA warning letters to online sellers, and Lilly has filed lawsuits over unapproved retatrutide [3].
SportCheck the current WADA Prohibited List.

Status checked 3 Nov 2026. Regulations changed several times in 2026, so check the linked sources for updates.

Part 3Evidence grade

Investigational

Randomized, double-blind, placebo-controlled phase 2 trials in people. It is not approved, and phase 2 trials are smaller and shorter than the phase 3 trials that support approval.

The peer-reviewed human evidence is randomized phase 2 trials. How we grade evidence.

Part 4What it is

Retatrutide is an investigational peptide that activates three hormone receptors at once: GIP, GLP-1 and glucagon. It is being developed for obesity and related conditions [1].

Part 5What studies found

Obesity (phase 2)

338 adults with obesity, or overweight with a weight-related condition, were randomized to weekly retatrutide (1 to 12 mg) or placebo for 48 weeks. At 48 weeks, mean weight change ranged from −8.7% (1 mg) to −24.2% (12 mg), versus −2.1% on placebo. In the 12 mg group, 83% lost 15% or more, versus 2% on placebo [1].

Type 2 diabetes (phase 2)

A separate double-blind, placebo- and active-controlled phase 2 trial in the USA studied retatrutide in people with type 2 diabetes [2].

Part 6Doses used in published studies

Not a recommendationThese are doses reported in published studies, listed with their population, route and duration so readers can understand the research. They are not instructions, and they say nothing about safety for you. Talk to a licensed clinician.
StudyPopulationRouteDose studiedDurationMain result
Phase 2 obesity [1]338 adults with obesity or overweightSubcutaneous, once weekly1, 4, 8 or 12 mg (some arms started lower)48 weeks−8.7% to −24.2% vs −2.1% body weight

Retatrutide has no approved dose. The doses above are trial doses, listed only so readers can understand the study.

Part 7Safety & adverse events

  • The most common adverse events were gastrointestinal. They were dose-related, mostly mild to moderate, and partly reduced by a lower starting dose [1].
  • Heart rate rose with dose, peaking at 24 weeks and then declining [1].
Report side effectsSuspected side effects can be reported to FDA MedWatch.

Part 8What is unknown

  • Long-term safety, and effects on outcomes such as heart attacks and strokes, are not established in peer-reviewed results.
  • Phase 3 results will determine whether it is approved. Until then, any product sold as retatrutide outside a clinical trial is unapproved and of unknown identity and quality [3].

Part 9Community discussion

Retatrutide will have its own moderated category when our forum opens. Personal experiences there are labeled as anecdotes, and claims about research must link a source.

Join the forum waitlist

Part 10References

  1. Jastreboff AM, et al. Triple-Hormone-Receptor Agonist Retatrutide for Obesity: A Phase 2 Trial. N Engl J Med. 2023;389(6):514-526. PubMed 37366315 · doi:10.1056/NEJMoa2301972
  2. Rosenstock J, et al. Retatrutide, 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. 2023;402(10401):529-544. PubMed 37385280 · doi:10.1016/S0140-6736(23)01053-X
  3. ArentFox Schiff. RUO-ined: Five Peptide Vendors Learn “Research Use Only” Is Not a Legal Strategy. 18 Sep 2026. afslaw.com
Educational information onlyThis profile summarizes published research. It is not medical advice and does not recommend using Retatrutide. Full medical disclaimer.