what the trials found
Retatrutide: What Happened to People in Trials
This drug isn't approved. Phase 3 and earlier trials tell us how much weight people lost and which health problems they had.
What do I need to know first?
You might first notice that food no longer calls to you. Retatrutide can curb hunger, but you can't fill a prescription for it. No health agency has approved the drug. Eli Lilly is testing it in Phase 3 trials.
An earlier Phase 2 trial followed 338 adults with obesity for 48 weeks. At the highest test amount, people lost 24.2% of their body weight on average. No similar drug had reached that mark in this kind of trial.
Retatrutide copies three messages the body already uses. Message 1 curbs hunger and slows food leaving your stomach. Another helps release insulin after you eat and affects stored fat. The third may make the body burn more fuel. Together, those actions may help explain the weight loss.
The good result came with health problems. Nausea was common, and it rose with the test amount. People's resting pulse also rose. We don't know the long-term risks because the trials aren't done. You can read outside reports on the effects page.
When you weigh that large change, remember it was an average from a group under trial care, so it can't promise what would happen in your body outside a trial.
How can retatrutide change hunger, sugar, and fat?
Retatrutide is a peptide, a small drug made from pieces of protein. Scientists joined many small pieces to make it. The drug has 1 job tied to hunger, 1 tied to blood sugar, and 1 tied to fuel use.
The first message curbs hunger and slows food leaving your stomach. The second helps your body release insulin when blood sugar rises. It also changes how the body handles fat. The third is the hormone glucagon. It helps the liver break down fat and may raise fuel use at rest [3].
Powerful lab pictures showed that retatrutide could join all three message sites [3]. The pictures explain how the drug may work. They can't tell how much weight one person will lose or whether the drug is safe for years.
In Phase 2, people given 12 mg lost 24.2% of their body weight on average after 48 weeks [1]. Phase 3 trials are asking if larger groups get much the same result.
What were the retatrutide results in Phase 2?
The clearest result came from the 48-week Phase 2 trial [1]. People given 12 mg each week lost 24.2% of their weight on average. The placebo group got shots with no drug and lost 2.1%. Other groups lost 22.8% at 8 mg, 17.3% at 4 mg, and 8.7% at 1 mg. More drug went with more weight loss.
A second Phase 2 trial followed 281 adults with type 2 diabetes for 36 weeks. With 12 mg, a blood test of their usual sugar fell 2.02 points after 24 weeks. That test looks back over about a 3-month span. Their weight fell 16.94% by week 36. With placebo, the blood test fell 0.01% and weight fell 3.00% [2]. No one had severe low blood sugar. No one died.
A third group had fatty liver. With 12 mg, the share of their liver made up of fat fell 82.4% after 24 weeks. Then 86% had liver fat below 5%, which doctors call normal [5]. That improvement still held at 48 weeks.
The full retatrutide results page covers Phase 1 and later reviews too.
Is retatrutide FDA approved yet?
No. Retatrutide is not FDA-approved. It is an investigational compound in Phase 3 clinical trials (Eli Lilly's TRIUMPH program). It is not a marketed drug. There is no approved drug label, no retail prescription to fill, and no lawful patient supply outside a clinical trial.
The distinction from semaglutide and tirzepatide matters: FDA-approved products containing those drugs can be prescribed. Retatrutide has no approved product and is still being tested. The timing of any filing, review, or approval remains uncertain.
What exists outside clinical trials is gray-market research-labeled material — unregulated, unverified for identity or purity, and outside any clinical oversight. See Retatrutide effects for the safety context.
That contrast is worth following through to how access works. For a concrete prescription comparison, Promise Peptides (mypromise.com) currently prescribes compounded tirzepatide, a related drug, rather than retatrutide. A clinician licensed in the U.S. checks the patient's history and may turn down the request. Only patients in the U.S. can use the service, and the choices differ across states and treatments. FDA-approved tirzepatide products exist, but the compounded preparation has no FDA approval. Retatrutide is investigational and is not part of that prescription service.
How do retatrutide and tirzepatide differ?
Both drugs copy 2 body messages tied to hunger and insulin. Retatrutide adds 1 more by copying glucagon, a hormone that helps the liver use stored fuel. That makes 2 shared messages plus the added fuel message. The added action may help explain the larger weight change.
Tirzepatide brought about 22.5% weight loss at 15 mg after 72 weeks in its Phase 3 trial. Retatrutide brought 24.2% at 12 mg after 48 weeks in Phase 2 [1][8]. The trials used different people, lengths, and rules. You can't use those separate results as a fair contest. Reviews still called the retatrutide result a large change for this drug family [6][8].
A Phase 3 trial is now comparing the two drugs directly [10]. There's no result yet, so no one can fairly say which works better for you.