Retatrutide: What Published Trials Show, and Its Status

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Quick facts

Fact sheet

U.S. status: Investigational
Strongest evidence: Human trials
Status verified: October 30, 2026

Retatrutide produced large average weight loss in published phase 3 trials, and it is still an experimental drug. Here is what the trials found, why two different headline numbers circulate, and what is not known.

Key takeaways

Retatrutide is investigational. It is not FDA-approved for any use. The company developing it, Eli Lilly, says it plans to submit an application to FDA in the first quarter of 2027. That is a company plan, not an approval timeline.
The published trials show large average weight loss. In TRIUMPH-1, published in a journal, adults with obesity lost an average of 25.0% of body weight on the highest dose studied, at 80 weeks, vs 3.9% on placebo.
Two numbers circulate for the same trial: 28.3% and 25.0%. They answer different statistical questions. We use the journal figure.
Long-term safety is unknown, and the trials show dose-related stomach side effects, unusual skin sensations and a rise in heart rate.
FDA says retatrutide cannot be used in compounding under federal law. There is no FDA-approved retatrutide product to buy.

What is retatrutide?

Retatrutide is an experimental injectable drug that acts on three hormone receptors (GIP, GLP-1 and glucagon), which is why it is called a triple agonist. Its relatives semaglutide and tirzepatide act on one or two of them and are FDA-approved. See our guides to semaglutide and tirzepatide.

Is retatrutide FDA-approved?

No. A search of FDA’s Drugs@FDA data on Oct. 31 found no product listed under that name. That search cannot show whether an application is pending, so the filing timeline comes from the company: Lilly says it plans to submit in the first quarter of 2027.

Can it be compounded or bought legally?

FDA says: “Retatrutide and cagrilintide cannot be used in compounding under federal law,” and that they “have not been found safe and effective for any condition” (FDA, Oct. 1, 2026). FDA says it has also warned telehealth companies, API distributors and outsourcing facilities over retatrutide. HHS’s Oct. 30, 2026 interim compounding policy covers six other peptides and does not include retatrutide (HHS policy).

The results below come from Lilly’s trials. They cannot be carried over to a product of unknown origin, and “research use only” labels did not stop FDA from treating such products as drugs for human use. We do not link to or recommend any seller.

What did the published trials find?

Every trial below is randomized and in people. Arms are shown as low, medium and high dose; this guide does not give doses. Results use the journals’ main analysis (the treatment-regimen estimand, explained below).

Trial	Who was studied	Average weight change
TRIUMPH-1 (NEJM), 2,339 adults, 80 weeks	Obesity, no diabetes	−17.6% low, −23.7% medium, −25.0% high vs −3.9% placebo
TRIUMPH-2 (Lancet), 1,152 adults, 80 weeks	Obesity and type 2 diabetes	−11.9%, −16.8%, −18.8% vs −5.1%
TRANSCEND-T2D-1 (Lancet), 537 adults, 40 weeks	Type 2 diabetes managed with diet and exercise alone	−11.5% to −15.3% vs −2.6%; HbA1c fell 0.88 to 1.12 points more than placebo
Phase 2 (NEJM), 338 adults, 48 weeks (registry)	Obesity or overweight	Up to −24.2% vs −2.1%

What about knee pain, sleep apnea and the liver?

Knee osteoarthritis: in a TRIUMPH-1 subgroup of 574 people, pain scores improved more than with placebo (differences of −1.4 and −1.6 in the intention-to-treat analysis for two dose arms) (TRIUMPH-1).
Sleep apnea: in a subgroup of 243, the apnea-hypopnea index differed from placebo by −24.7 and −22.5 events per hour for two dose arms (same analysis).
Fatty liver: a small phase 2a trial (98 people, 24 weeks) found liver fat fell by up to 82.4% vs a rise of 0.3% on placebo. That is an imaging measure, not a clinical outcome, in a small sample.

These are subgroups and an early-phase trial. They are signals, not proof of benefit for those conditions.

Why do you see 28% in headlines and 25% in the journal?

For TRIUMPH-1, Lilly’s May release gives 28.3% on the highest dose; NEJM reports 25.0%. For TRIUMPH-2, Lilly’s September release gives 20.8%; The Lancet reports 18.8%.

The reason is a statistical choice. Lilly labels its higher figures the “efficacy estimand,” which it defines as the effect had all randomized participants remained on treatment. The journal figures use the treatment-regimen estimand, which Lilly describes as the average effect regardless of whether people kept taking the drug or started prohibited weight-loss treatments. Lilly’s May release gives the same 25.0% under that estimand. Neither is wrong, and they answer different questions.

What to do with that: use the journal figure as the main one, and do not set a company’s 28% beside journal figures for other drugs.

What did Lilly report against Ozempic?

On Oct. 28, 2026, Lilly reported topline results from an open-label trial in adults with type 2 diabetes comparing retatrutide with Ozempic 2 mg (Lilly). Under its efficacy analysis, which assumes participants stayed on treatment, A1C fell 2.2 points on retatrutide (medium and high dose) versus 1.8 on Ozempic, and weight fell 19.5% to 20.9% versus 9.4%. The results have not been published in a peer-reviewed journal.

Two cautions. These are company results, open-label, and from the efficacy analysis, so do not compare them with the journal figures above. And the comparison is with Ozempic’s top dose for diabetes, not Wegovy for obesity, so “more than double the weight loss of Wegovy” would be wrong.

Is retatrutide better than tirzepatide?

Unknown. We found no published head-to-head result; a trial of that kind is listed as still active.

What are the risks?

There is no prescribing label. This is what was observed in trials.

Stomach effects, dose-related. In TRIUMPH-2, nausea occurred in 14%, 21% and 28% across the three dose arms vs 8% on placebo.
Blood pressure and skin sensations. Low blood pressure in up to 6% vs under 1%, and abnormal skin sensations (dysesthesia) in up to 7% vs 1% (TRIUMPH-2).
Stopping treatment. Stopping because of side effects or death was 4%, 12% and 8% in TRIUMPH-2 vs 5% on placebo. For TRIUMPH-1, a figure we have only from the company, Lilly reports stopping because of side effects at 4.1%, 6.9% and 11.3% vs 4.9%.
Deaths. Six people across the retatrutide groups and one on placebo died in TRIUMPH-2; the investigators deemed the deaths unrelated to treatment.
Heart rate. Heart rate rose with dose in the phase 2 trial, peaking at week 24 (phase 2).
Company-reported, TRIUMPH-1 (Lilly): nausea 28.6%, 38.4% and 42.4% vs 14.8%; dysesthesia 5.1%, 12.3% and 12.5% vs 0.9%; urinary tract infection 7.5%, 8.8% and 8.4% vs 5.3%. Lilly says dysesthesia and infections were generally mild or moderate.
Long-term safety is not established; trials are ongoing.

What is still unknown?

Heart and kidney outcomes. A large outcomes trial, registered with a planned enrollment of 10,000, is active and has no results.
Whether lean mass and strength hold up. In a phase 2 substudy in type 2 diabetes (189 enrolled, 103 with both scans, 36 weeks; funded by Lilly, with Lilly-employed authors), the authors say the share of weight lost as lean mass was similar to other obesity treatments. We read the abstract only, and it does not give that share. We found no data on strength.
Safety beyond the trial window.

Which claims are not supported?

“You can get it legally from a compounding pharmacy.” FDA says it cannot be compounded.
“It’s already approved,” or “about to be.” Lilly says it plans to file in the first quarter of 2027.
“Research-use-only vials are the trial drug.” Nothing we reviewed supports that.
“30% weight loss for everyone.” The journal’s average for all participants on the highest dose in TRIUMPH-1 was 25.0%.
“Better than tirzepatide” or “better than Wegovy.” No published comparison supports either.

What should you ask your doctor?

Is there an FDA-approved treatment for my goal, and what does the evidence say about it?
Am I eligible for any clinical trial, and what would taking part involve?
If someone offers me retatrutide outside a trial, what is it, who made it, and how would anyone know what is in it?

Frequently asked questions

Is retatrutide approved by the FDA?

No. It is investigational, and Lilly says it plans to file in the first quarter of 2027.

How much weight do people lose on retatrutide?

In the NEJM-published TRIUMPH-1 trial, adults with obesity lost an average of 25.0% on the highest dose at 80 weeks vs 3.9% on placebo. Lilly’s 28.3% uses a different analysis.

Is retatrutide safe?

Its long-term safety is unknown. Trials show dose-related stomach effects, abnormal skin sensations and a rise in heart rate.

Where can I buy retatrutide?

There is no FDA-approved product, and FDA says it cannot be used in compounding under federal law.

Sources we checked

TRIUMPH-1 trial, retatrutide in obesity, NEJM (PubMed)PubMed. Accessed October 30, 2026.
TRIUMPH-2 trial, retatrutide in obesity and type 2 diabetes, Lancet (PubMed)PubMed. Accessed October 30, 2026.
TRANSCEND-T2D-1 trial, retatrutide in type 2 diabetes, Lancet (PubMed)PubMed. Accessed October 30, 2026.
Retatrutide phase 2 trial in obesity, NEJM (PubMed)PubMed. Accessed October 30, 2026.
Retatrutide phase 2a trial in fatty liver disease, Nature Medicine (PubMed)PubMed. Accessed October 30, 2026.
Lilly press release on retatrutide TRIUMPH-1, May 21, 2026Press release. Accessed October 30, 2026.
Lilly press release on retatrutide TRIUMPH-2, Sept. 29, 2026Press release. Accessed October 30, 2026.
Lilly press release on retatrutide TRANSCEND-T2D-2 vs Ozempic, Oct. 28, 2026Press release. Accessed October 30, 2026.
ClinicalTrials.gov NCT06383390 (cardiovascular and renal outcomes trial, active)ClinicalTrials.gov. Accessed October 30, 2026.
ClinicalTrials.gov NCT06662383 (retatrutide comparison trial, active)ClinicalTrials.gov. Accessed October 30, 2026.
Retatrutide body composition substudy, Lancet Diabetes Endocrinol 2025 (PubMed)PubMed. Accessed October 31, 2026.
FDA warning letter to Royal Peptides, Aug. 24, 2026FDA. Accessed October 31, 2026.
Drugs@FDA (searched Oct. 31, 2026; no product listed as retatrutide)FDA. Accessed October 31, 2026.
FDA's concerns with unapproved GLP-1 drugs used for weight lossFDA. Accessed October 30, 2026.
HHS: Enforcement Discretion Policy, with Appendices A and BOther. Accessed October 31, 2026.

Written and maintained by the Best Peptides For Editorial Team. How we rate evidence.