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What is retatrutide?
Retatrutide is an experimental weekly injection from Eli Lilly that has produced some of the largest weight-loss results ever reported in a Phase 3 trial. It isn’t approved anywhere yet, but the timeline is getting short. Here is what the trials show, what the side effects look like, and when you could realistically get it.
Where things stand (updated November 1, 2026): Retatrutide is not FDA approved. Lilly said on July 23, 2026 that it plans to submit its application to the FDA in the first quarter of 2027. Until then it is legally available only to people enrolled in Lilly’s clinical trials.
What is retatrutide?
Retatrutide is an investigational, once-weekly injection that activates three hormone receptors at once: GIP, GLP-1, and glucagon. It is a single molecule, not a combination of drugs.
That is what sets it apart from the medications already on the market. Semaglutide (Wegovy, Ozempic) targets GLP-1. Tirzepatide (Zepbound, Mounjaro) targets GIP and GLP-1. Retatrutide adds the glucagon receptor, which is involved in how the body uses energy, and that is the reason researchers are watching it closely.
What did the Phase 3 trials show?
Lilly’s TRIUMPH program is a set of large Phase 3 trials in people with obesity and related conditions. The first major result, TRIUMPH-1, enrolled 2,339 adults with obesity or overweight and at least one weight-related health condition, none of whom had type 2 diabetes. Participants took 4 mg, 9 mg, or 12 mg weekly, or a placebo, for 80 weeks.
| Dose | Efficacy estimand | Treatment-regimen estimand |
|---|---|---|
| Retatrutide 4 mg | −19.0% | −17.6% |
| Retatrutide 9 mg | −25.9% | −23.7% |
| Retatrutide 12 mg | −28.3% | −25.0% |
| Placebo | −2.2% | −3.9% |
Why are there two sets of numbers?
You will see headlines quoting different figures for the same trial, and both are legitimate. The efficacy estimand measures the effect while people were still taking the drug as directed. The treatment-regimen estimand measures the effect across everyone assigned to the drug, whether or not they stayed on it or started other weight-loss treatments. The second number is usually lower and is closer to what happens in everyday life. Whenever you see a weight-loss figure, check which one it is.
Other results worth knowing
- At the 12 mg dose, 45.3% of participants lost 30% or more of their body weight (efficacy estimand), a level long associated with bariatric surgery.
- In a 104-week extension for people with a starting BMI of 35 or higher, those who stayed on 12 mg lost an average of 30.3% (efficacy estimand).
- Lilly reported improvements in waist circumference, triglycerides, non-HDL cholesterol, systolic blood pressure, and an inflammation marker (hsCRP).
- In July 2026, Lilly reported that TRIUMPH-2 and TRIUMPH-3 also met their primary endpoints, with weight loss of up to 22.6% at 80 weeks in people with major cardiometabolic conditions.
How does it compare with Zepbound and Wegovy?
On the treatment-regimen measure, tirzepatide reached up to 20.9% in its pivotal obesity trial and high-dose semaglutide reached 18.7%, against 25.0% for retatrutide 12 mg. These come from separate trials with different participants, so they are a rough guide and not a head-to-head comparison. No trial has yet pitted retatrutide directly against either drug.
What are the side effects?
Lilly describes the safety profile in TRIUMPH-1 as generally consistent with other drugs in this class. Stomach and intestinal problems were the most common, and they rose with the dose.
- Nausea: 28.6% (4 mg), 38.4% (9 mg), and 42.4% (12 mg), versus 14.8% on placebo.
- Stopping because of side effects: 4.1% (4 mg), 6.9% (9 mg), and 11.3% (12 mg), versus 4.9% on placebo.
The doses were raised gradually, starting at 2 mg and stepping up every four weeks, which is standard for this class and helps with tolerability. Full safety data will come with the peer-reviewed publications and the FDA review.
When can you get retatrutide?
Lilly has said it plans to file in the first quarter of 2027, and it also plans to seek approval for obesity with knee osteoarthritis pain and for obesity with obstructive sleep apnea. After a filing, the FDA review typically takes months, and no approval date or price has been announced. The only legitimate way to get it today is to qualify for a clinical trial, which you can search on ClinicalTrials.gov.
Don’t buy “research peptides” sold as retatrutide.
Because demand is high and the drug isn’t approved, many websites sell products labelled as retatrutide. It can’t legally be purchased, prescribed, or compounded, so anything sold this way is not the real, quality-controlled drug. These products can be mislabelled, contaminated, or the wrong dose, and you would be injecting them with no medical oversight. If you want to lose weight now, there are approved medications and other options you can discuss with a clinician.
Frequently asked questions
Is retatrutide FDA approved?
No. It is an investigational drug. Lilly plans to submit its FDA application in the first quarter of 2027.
How much weight did people lose on retatrutide?
In TRIUMPH-1, people on the 12 mg dose lost an average of 28.3% of their body weight at 80 weeks (efficacy estimand) or 25.0% (treatment-regimen estimand). Results vary a lot from person to person.
Is retatrutide stronger than tirzepatide?
The results so far look larger, but the two have not been compared directly in the same trial, so it isn’t possible to say for certain yet.
Can I buy retatrutide online?
No legitimate source sells it. Products marketed as retatrutide are not the approved, quality-controlled drug and may be unsafe.
How is retatrutide different from semaglutide?
Semaglutide activates one receptor (GLP-1). Retatrutide activates three (GIP, GLP-1, and glucagon).
Sources
- Eli Lilly: Retatrutide delivered powerful weight loss in pivotal Phase 3 obesity trial (May 21, 2026)
- HCPLive: Retatrutide meets Phase 3 weight-loss endpoints in 2 obesity trials (July 23, 2026)
- Fierce Biotech: Lilly’s triple-G drug drives deep weight loss in Phase 3 obesity trial
- Drugs.com: Retatrutide FDA approval status
This article is for general information and is not medical advice. Retatrutide is an investigational drug, and the data described here may change as more results are published. Talk to your doctor or pharmacist before starting or changing any weight-loss treatment.
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