Peptide · Fact sheet
Retatrutide
Also known as LY3437943
Retatrutide activates GIP, GLP-1, and glucagon receptors and is being studied in Phase 3 programs. It is not an FDA-approved medicine.
What is Retatrutide?
Retatrutide is a manufactured peptide designed to activate three metabolic signaling receptors.
It remains a research drug. Registered trials are testing both benefits and risks in defined populations.
Benefits people look for
Early human studies reported substantial average weight changes, which generated strong public interest.
Phase 3 trials are intended to test whether those results hold up in larger, more diverse groups and to characterize safety more completely.
What the evidence supports
- Earlier trials observed changes in body weight and metabolic measures.
- Company-reported Phase 3 top-line results describe substantial weight changes in defined trial populations, but those reports should not be treated as FDA approval or complete published evidence.
- Ongoing Phase 3 and outcomes trials are designed to provide more reliable estimates of benefits and harms over time.
All research areas
- Obesity and overweight
- Type 2 diabetes
- Cardiovascular and kidney outcomes
- Obstructive sleep apnea
- Knee osteoarthritis in people with obesity or overweight
- Body-weight reduction and maintenance
- Metabolic and cardiovascular outcomes
- Obesity-related conditions
Anecdotal reports & lived experiences
Reports describe what someone noticed. They cannot establish cause, typical results, or how often a side effect happens.
Fatigue and skin tingling without a clear appetite change
A person using a product labeled retatrutide reported intense afternoon fatigue and skin tingling, with little perceived change in appetite. They also reported ongoing semaglutide exposure.
This is not a verified clinical-trial participant. Combined exposure and unknown product identity prevent assignment of symptoms to retatrutide; it cannot estimate trial safety or efficacy.
Read the reported experience ↗Side effects & risks
- Earlier trials reported gastrointestinal adverse effects, among other events.
- A research program may identify uncommon or longer-term risks only after larger and longer studies.
- Products marketed online as retatrutide are not an FDA-approved version of the investigational drug.
This is a summary of the cited evidence, not a complete product label. A lack of human safety data does not establish safety.
Clinical research: how strong is it?
Moderate human evidenceA published Phase 2 obesity trial and company-reported Phase 3 top-line results provide human evidence, but peer-reviewed Phase 3 publications, full regulatory review, and longer outcomes data remain pending.
Selected research to read
Registered Phase 3 obesity master trial with knee-osteoarthritis and obstructive-sleep-apnea substudies.
Registered Phase 3 comparison of retatrutide and tirzepatide in adults with obesity.
Registered cardiovascular and kidney outcomes trial.
Peer-reviewed Phase 2 dose-finding obesity trial that preceded the Phase 3 program.
What do the human studies show?
Selected research questions, not a complete inventory of indications or trials. Source checking is not independent clinical review. How we read the evidence.
| Study and people | Question and follow-up | Result and limits |
|---|---|---|
| Retatrutide Phase 2 Adults with obesity or overweight plus a weight-related condition 338 participants (actual) Randomized placebo-controlled trial; human | Retatrutide versus Placebo 48 weeks; primary endpoint at 24 weeks Primary: Percentage body-weight change at week 24 Weight change at week 48 was secondary, not the primary endpoint. Phase: Phase 2 | Greater weight reductions than placebo were reported. Cannot tell us: A Phase 2 result is neither approval nor a direct comparison with semaglutide or tirzepatide. Safety, uncertainty, and source detailsGastrointestinal events and increases in heart rate were reported. Limited to the studied population, formulation and follow-up. Funding/conflicts: Funded by Eli Lilly; individual disclosures not fully extracted. Source checked: 2026-09-18. Independent clinical review: not completed. |
| TRIUMPH-1 Adults with obesity or overweight; defined substudies 2,335 participants (actual) Randomized placebo-controlled trial; human | Retatrutide versus Placebo Primary weight endpoint: 80 weeks Primary: Body-weight change; subgroup apnea and knee-pain outcomes Phase: Phase 3 | Registry marks the study completed; no results are posted in this registry snapshot. Cannot tell us: No posted registry results does not mean no results exist elsewhere. Publication search is not complete. Safety, uncertainty, and source detailsSee primary paper; absence of a signal in this study does not establish general safety. Limited to the studied population, formulation and follow-up. Funding/conflicts: Sponsor: Eli Lilly and Company. Source checked: 2026-09-18. Independent clinical review: not completed. |
| TRIUMPH-5 Adults with obesity 800 participants (estimated) Randomized placebo-controlled trial; human | Retatrutide versus Tirzepatide Primary weight endpoint: 80 weeks Primary: Percentage body-weight change Phase: Phase 3 | Active, not recruiting; no registry results posted at the source check. Cannot tell us: A registered head-to-head design is not a completed head-to-head result. Enrollment is estimated. Safety, uncertainty, and source detailsSee primary paper; absence of a signal in this study does not establish general safety. Limited to the studied population, formulation and follow-up. Funding/conflicts: Sponsor: Eli Lilly and Company. Source checked: 2026-09-18. Independent clinical review: not completed. |
What these results can and cannot tell us
How do the Phase 2 publication and Phase 3 registry records differ?
Published Phase 2 weight outcomes and separate Phase 3 records can be inspected individually.
Limit: Registration, completion, company announcements and FDA approval are different events.
Check the sources: Retatrutide Phase 2 obesity trial (checked 2026-09-18) · TRIUMPH-1 registry record (checked 2026-09-18) · TRIUMPH-5 registry record (checked 2026-09-18)
Compare research questions · Submit a source-based correction
FDA approval & research status
Retatrutide is not FDA approved. Some Phase 3 studies have reported company-provided top-line results, while other Phase 3, head-to-head, and outcomes studies remain ongoing or active in registries.
No FDA-approved use is documented in the records summarized on this page.
Late-stage clinical development
Retatrutide has Phase 3 trial records and company-reported top-line results, while other Phase 3 and outcomes studies remain in the registry. It is not FDA approved.
This summarizes the cited product or research record. Trial phases do not establish successful completion of earlier stages, and a stopped program is not ongoing development. Approval applies only to the labeled product, use and population.
What we still don’t know
- How company-reported Phase 3 top-line findings will look after full peer-reviewed publication and regulatory review
- The complete adverse-effect profile across larger populations
- Which indications, populations, or product presentations might eventually be reviewed by regulators
- Long-term cardiovascular and kidney outcomes
The takeaway
Retatrutide is promising research, not an approved treatment. Phase 3 results and regulatory review—not online availability or early headlines—will determine what claims are supported.
Sources & further reading
Medical evidence and regulatory sources are listed here. Personal reports are linked separately in the experiences section.
- 1clinical trialsClinicalTrials.gov: TRIUMPH-1 Phase 3 study
Registered Phase 3 obesity master trial with knee-osteoarthritis and obstructive-sleep-apnea substudies.
- 2company releaseLilly: TRIUMPH-1 top-line results
Company-provided Phase 3 top-line obesity results; not a peer-reviewed publication or FDA approval.
- 3clinical trialsClinicalTrials.gov: TRIUMPH-5 Phase 3 study
Registered Phase 3 comparison of retatrutide and tirzepatide in adults with obesity.
- 4clinical trialsClinicalTrials.gov: TRIUMPH-Outcomes
Registered cardiovascular and kidney outcomes trial.
- 5pubmedNEJM Phase 2 obesity trial indexed in PubMed
Peer-reviewed Phase 2 dose-finding obesity trial that preceded the Phase 3 program.