Skip to content
PeptidesEncyclopedia
For research use only

Not for human consumption. Consult a licensed professional.

Research chemical — not approvedaka LY3437943

Retatrutide — Complete Research Guide (2026)

Last updated 2026-06-25

TL;DR

An investigational triple GIP/GLP-1/glucagon receptor agonist in late-stage clinical trials for obesity; not yet approved.

What is Retatrutide?

Retatrutide (LY3437943) is an investigational once-weekly single-molecule agonist of the GIP, GLP-1, and glucagon receptors, developed by Eli Lilly for obesity and type 2 diabetes.

It is NOT approved by the FDA, EMA, or any regulator and remains in clinical trials; the strongest published human evidence to date is randomized phase 2 (obesity, type 2 diabetes, and MASLD), with phase 3 trials ongoing.

Because it is unapproved and investigational, any use outside a supervised clinical trial is not legally marketed for human treatment.

How does Retatrutide work?

Retatrutide simultaneously activates three metabolic hormone receptors: GLP-1 and GIP receptors reduce appetite and improve glycemic control, while glucagon-receptor activation is thought to add increased energy expenditure and hepatic fat mobilization.

This triple-agonist design is intended to combine caloric-intake reduction with raised energy expenditure, distinguishing it from single (GLP-1) or dual (GIP/GLP-1) agonists. [INFOGRAPHIC: Triple GIP/GLP-1/glucagon receptor agonism]

What does the research say about Retatrutide?

  • In a 48-week phase 2 obesity trial (n=338), the 12 mg dose produced roughly 24% mean body-weight reduction, and 83% of participants lost at least 15% of body weight versus 2% on placebo. [1]
  • In adults with type 2 diabetes, retatrutide lowered HbA1c by up to about 2.0% and reduced body weight by up to ~17% over the phase 2 trial period versus near-zero change on placebo. [2]
  • In a 24-week phase 2a MASLD trial, higher doses reduced liver fat by ~81-82% relative to baseline and normalized liver fat (<5%) in up to 86% of participants. [3]

Clinical research & studies

The references below are the primary sources cited throughout this guide. Each links directly to PubMed or the regulator. Where evidence is preclinical (animal or in-vitro), that is stated rather than implied.

  • [1] Triple-Hormone-Receptor Agonist Retatrutide for Obesity - A Phase 2 Trial — Jastreboff AM et al., N Engl J Med 2023. (RCT (phase 2, n=338))
  • [2] 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 — Rosenstock J et al., Lancet 2023. (RCT (phase 2))
  • [3] Triple hormone receptor agonist retatrutide for metabolic dysfunction-associated steatotic liver disease: a randomized phase 2a trial — Sanyal AJ et al., Nat Med 2024. (RCT (phase 2a))
  • [4] LY3437943, 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 — Urva S et al., Lancet 2022. (RCT (phase 1b))
  • [5] LY3437943, a novel triple glucagon, GIP, and GLP-1 receptor agonist for glycemic control and weight loss: From discovery to clinical proof of concept — Coskun T et al., Cell Metab 2022. (preclinical + phase 1 proof of concept)

Dosing context

This is not medical advice or a usage recommendation. Dosing figures are reported research context only, cited from the published literature.

Published trials used once-weekly subcutaneous injection with gradual dose escalation (e.g., starting at 2 mg and titrating toward 8-12 mg) specifically to limit gastrointestinal side effects.

These figures describe trial protocols only and are not a dosing recommendation; there is no approved dose and no legitimate non-trial supply.

Side effects & safety profile

Across trials the most common adverse events were dose-related gastrointestinal effects (nausea, vomiting, diarrhea, constipation), mostly mild-to-moderate and partly mitigated by lower starting doses and dose escalation.

Dose-dependent increases in heart rate were observed, and long-term safety and cardiovascular outcomes are not yet established because no phase 3 outcome trials have reported.

As an unapproved investigational drug, its safety profile is based only on relatively short (up to ~48-week) phase 1-2 studies in supervised settings.

Stacking & combinations

Retatrutide is studied as a standalone agent, and combining an unapproved triple agonist with other GLP-1-class drugs or glucose-lowering agents is unstudied and risks additive gastrointestinal and hypoglycemia effects.

Finding Retatrutide vendors

Finding Retatrutide vendors

This is an independent, neutral directory — we sell nothing and route no purchases. Use it to read regulatory context and (where available) genuine, moderated vendor information for your country.

Choose your country

We never list placeholder vendors. Pick your country to see neutral regulatory context.

Browse the directory

User reviews

No reviews yet

Reviews appear here once submitted and moderated. An aggregate rating is shown only after at least 5 genuine reviews — we never fabricate ratings.

Sign in to review

Frequently asked questions

No. Retatrutide is an investigational drug still in clinical trials and is not approved by the FDA, EMA, or any regulator. It is not legally marketed for treatment.

References

  1. [1] Triple-Hormone-Receptor Agonist Retatrutide for Obesity - A Phase 2 Trial — Jastreboff AM et al., N Engl J Med 2023. PMID: 37366315. View sourceStudy: RCT (phase 2, n=338)Retatrutide produced substantial dose-dependent weight loss, up to ~24% at 48 weeks with the 12 mg dose.
  2. [2] 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 — Rosenstock J et al., Lancet 2023. PMID: 37385280. View sourceStudy: RCT (phase 2)Retatrutide gave clinically meaningful HbA1c reductions (up to ~2.0%) and robust weight loss in type 2 diabetes.
  3. [3] Triple hormone receptor agonist retatrutide for metabolic dysfunction-associated steatotic liver disease: a randomized phase 2a trial — Sanyal AJ et al., Nat Med 2024. PMID: 38858523. View sourceStudy: RCT (phase 2a)Retatrutide markedly reduced liver fat, normalizing it (<5%) in up to 86% of participants at 24 weeks.
  4. [4] LY3437943, 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 — Urva S et al., Lancet 2022. PMID: 36354040. View sourceStudy: RCT (phase 1b)Multiple ascending doses had an acceptable safety profile with robust glucose and weight reductions, supporting phase 2.
  5. [5] LY3437943, a novel triple glucagon, GIP, and GLP-1 receptor agonist for glycemic control and weight loss: From discovery to clinical proof of concept — Coskun T et al., Cell Metab 2022. PMID: 35985340. View sourceStudy: preclinical + phase 1 proof of conceptGlucagon-receptor activity added energy-expenditure-driven weight loss to GIP/GLP-1 appetite reduction in models and early human data.

Related peptides

SemaglutideWeight Loss & MetabolicTirzepatideWeight Loss & Metabolic
This article is for educational and research purposes only. Peptides discussed here are not approved for human consumption by the FDA, EMA, or equivalent regulators outside of specific clinical contexts. Always consult a licensed medical professional before any therapeutic use.