Is Retatrutide FDA Approved? Trial Results, Side Effects and When You Could Get It

No. Retatrutide is not FDA-approved as of October 2026, and Lilly says it is legally available only to people in its clinical trials¹. In the TRIUMPH-1 trial, people on the 12 mg dose lost an average of 28.3% of body weight at 80 weeks². Lilly plans to submit it to the FDA in the first quarter of 2027³.

That gap between strong trial results and no approval is why the name is everywhere right now. This guide covers where retatrutide stands with regulators, what the trials found, which side effects showed up, how it differs from tirzepatide, and what you can get with a prescription today.

Is retatrutide approved, and when could it be?

Not yet, anywhere. Lilly's own retatrutide page says it "has not been approved by any regulatory agency" and that it remains an investigational medicine being studied in clinical trials¹. Here is how the program has moved, using Lilly's dated announcements:

Lilly's July release explains the timing: it is finishing the chemistry, manufacturing and controls package the FDA requires and "plans to subsequently submit retatrutide in Q1 2027 for U.S. approval"³. Submission starts an FDA review; it is not an approval. Lilly has not published an expected approval date, and we don't print one. On price, Lilly says only that it plans to price retatrutide "to reflect the overall value to the healthcare system" after approval¹.

How much weight did people lose?

A lot, at every dose tested, though each trial enrolled different people. The table shows average weight change by dose in Lilly's trials:

Two things help when reading those numbers. First, the TRIUMPH figures above are Lilly's "efficacy estimand," which estimates the result if everyone had stayed on treatment. Counting everyone who was randomized, including people who stopped, TRIUMPH-1 showed -17.6%, -23.7% and -25.0% against -3.9% on placebo, the figures the published paper leads with^2,6. Second, people with type 2 diabetes usually lose less weight on these drugs, which is why TRIUMPH-2 sits lower.

TRIUMPH-1 also ran a blinded extension for 532 participants who started with a BMI of 35 or more. Those who continued to 104 weeks on the top dose averaged 30.3% weight loss². In the same trial, 45.3% of people on 12 mg lost at least 30% of their body weight at 80 weeks².

What are the side effects?

Mostly the stomach effects you'd expect from this drug family, plus a skin-sensation effect that stands out. In TRIUMPH-1 the most common side effects were, for the 4, 9 and 12 mg doses against placebo²:

Lilly describes the dysesthesia and urinary tract infection events as generally mild to moderate, and says most resolved while people stayed on treatment². Urinary tract infections ran at 7.5% to 8.8% on retatrutide against 5.3% on placebo². In the phase 2 trial, heart rate rose with dose, peaked at 24 weeks and then declined, and stomach side effects were partly reduced by starting at 2 mg rather than 4 mg⁵. In TRIUMPH-3, which enrolled people with heart disease, 13.5% on the 12 mg dose stopped because of side effects, against 4.8% on placebo³.

How is retatrutide different from tirzepatide?

It adds a third hormone target. Tirzepatide (Zepbound, Mounjaro) acts on two receptors, GIP and GLP-1. Retatrutide acts on those two plus the glucagon receptor, which is why Lilly calls it a "triple agonist"². Both are once-weekly injections made by Lilly.

The weight-loss numbers look larger for retatrutide, but they come from different trials. In SURMOUNT-1, tirzepatide 15 mg produced 20.9% average weight loss at 72 weeks, against 3.1% on placebo⁹. TRIUMPH-1 ran longer (80 weeks) with different participants, so the two results aren't a fair head-to-head. That comparison is coming: TRIUMPH-5 is a double-blind trial of retatrutide against tirzepatide in about 800 adults with obesity, measuring weight change at 80 weeks, with primary results estimated for November 2026 on ClinicalTrials.gov⁸.

For now, the practical difference is simple: tirzepatide is approved and you can get it with a prescription. Retatrutide isn't. If you're comparing the approved options, our Zepbound vs. Wegovy guide covers the only head-to-head trial between them.

Is "research" retatrutide safe or legal to buy?

No. Lilly says anything sold to consumers outside its trials "is illegal, with no way to verify its safety, purity or dosing"¹. The FDA goes further on two points⁷:

• It can't be compounded. FDA states that retatrutide cannot be used in compounding under federal law, because it is not a component of any FDA-approved drug and has not been found safe and effective for any condition. A pharmacy that offers "compounded retatrutide" is offering something the law doesn't allow.
• "For research purposes" labels don't make it legal. FDA has warned companies selling retatrutide labeled "for research purposes" or "not for human consumption" to consumers with dosing instructions, and has warned telehealth companies for marketing it directly to consumers.

Some telehealth programs and peptide sites do list retatrutide. We don't link to any of them as a source of the drug, and this page gives no dosing information for it. If a seller offers it, treat that as a reason to look at the rest of what that seller does with extra care.

What can you take now?

An approved GLP-1, with a prescription. The closest relative is tirzepatide, made by the same company. Here is what the main cash routes cost in October 2026:

The compounded figures come from our price index and usually include the clinician visit. The FDA notes that compounded drugs are not FDA-approved, so it does not check their safety, effectiveness or quality before they're sold¹³. That's a real difference from the brand-name products, but it isn't the same as retatrutide's status: compounded semaglutide and tirzepatide copy approved drugs, while retatrutide has no approved version at all. For the full tirzepatide price picture, see tirzepatide cost without insurance.

What to do next

If you were hoping to start retatrutide, the realistic path today is an approved drug now and a conversation with your clinician once retatrutide's FDA review is complete. Results on the approved drugs are substantial: tirzepatide's top dose averaged about 21% weight loss in its main trial⁹.

If you want tirzepatide, the tirzepatide board lists telehealth programs with their month-to-month prices. CoreAge Rx (Partner) sells compounded tirzepatide at one flat price at every dose.

If you want a brand-name drug, the brand-name GLP-1 board lists programs that prescribe Zepbound and Wegovy. If you'd rather take a pill, our guide to Foundayo cost and how to get it covers the newest one.

Not sure which fits? The 2-minute quiz asks about budget, medication preference and insurance, then matches you with programs that fit. For the molecule-level comparison, read semaglutide vs. tirzepatide.