Retatrutide: what the trials show and where it stands with FDA

Retatrutide is the next drug in the line that runs from semaglutide to tirzepatide. Each one acts on one more gut-hormone receptor than the last. The trial numbers are striking. The status is simple: right now, retatrutide isn't approved, can't be prescribed as a marketed drug, and can't be legally compounded.

Retatrutide is a triple-hormone drug still in trials

Retatrutide activates three receptors at once: GIP, GLP-1 and glucagon. The trial papers call it a “triple hormone receptor agonist” ^[4]. Semaglutide acts on GLP-1 alone. Tirzepatide adds GIP. Retatrutide adds glucagon on top.

Why glucagon? It's the hormone that normally raises blood sugar, so adding it to a diabetes-and-weight drug sounds odd. The idea researchers are testing is that glucagon's effects on energy use and the liver add to the appetite effects of the other two. The trials show the combined drug lowers both weight and blood sugar. Exactly how much each receptor contributes in people isn't settled.

It's given as a once-weekly injection in every published trial. Because there's no FDA label, there's no approved dose, no approved patient group and no full safety profile. The doses you'll see below are trial arms, not recommendations.

Retatrutide has no approved use; it's being tested for obesity and related conditions

What is retatrutide used for? Nothing yet, officially. It has no approved use. Lilly is testing it for obesity, type 2 diabetes, knee osteoarthritis pain and obstructive sleep apnea. TRIUMPH-1 included a subgroup of 574 people with knee osteoarthritis and 243 with sleep apnea, and found improvements in both ^[4].

That breadth is part of why retatrutide gets so much attention. The longevity question, whether it lowers heart attacks, strokes or deaths, hasn't been answered. No cardiovascular-outcome results have been published.

Phase 3 trials showed up to 25% average weight loss at 80 weeks

In TRIUMPH-1, 2,339 adults with obesity and no diabetes took weekly retatrutide or placebo for 80 weeks. Weight fell 17.6%, 23.7% and 25.0% on the 4, 9 and 12 mg arms, against 3.9% on placebo ^[4].

TRIUMPH-2 is the reality check for people with diabetes. Weight loss was smaller, as it is with every drug in this class, topping out at 18.8% on the highest arm ^[5]. In TRANSCEND-T2D-1, retatrutide on its own lowered A1C by up to 1.94 points in people whose diabetes wasn't controlled by diet and exercise ^[6].

In the knee osteoarthritis subgroup of TRIUMPH-1, pain scores improved by 3.4 to 4.1 points on retatrutide against 2.5 on placebo, on a 10-point scale ^[4]. In the sleep apnea subgroup, breathing interruptions fell by 32.1 to 34.3 events an hour on the two higher arms, against 9.6 on placebo.

Side effects so far are mostly stomach-related, with a heart-rate signal

Across the trials, the most common side effects were gastrointestinal, and they rose with dose. In the phase 2 trial they were mostly mild to moderate, and heart rate rose in a dose-dependent way, peaking at 24 weeks and then declining ^[7]. In TRANSCEND-T2D-1, 2% to 5% of people on retatrutide stopped because of side effects, against none on placebo, and no severe low blood sugar was reported ^[6].

That's an incomplete picture by design. Trials are built to find benefits and common harms. Rare side effects, long-term effects and interactions usually show up in larger, longer use, and FDA's review would set out the official safety profile in a label. Retatrutide doesn't have one yet.

FDA hasn't approved retatrutide, and it can't legally be compounded

Right now, retatrutide isn't approved for any use and isn't on FDA's list of 2026 novel drug approvals ^[2]. FDA states plainly that “retatrutide and cagrilintide cannot be used in compounding under federal law” ^[1]. That's different from semaglutide and tirzepatide, which pharmacies may still compound in narrow cases because they're ingredients in approved drugs.

Can you get retatrutide outside a trial? Trials are the main route. Lilly also lists a single-patient expanded access program, which a treating physician has to request. It's limited to adults with severe obesity (a BMI of 35 or more plus at least two serious or life-threatening complications) who haven't responded to approved treatments and can't join a trial ^[3]. For the legal side in detail, read whether retatrutide can be obtained legally.

Why “retatrutide” sold online is not the trial drug

Anything sold online as retatrutide in 2026 is an unapproved product, not the drug Lilly tested. FDA has warned companies that illegally sold unapproved drugs containing retatrutide and similar compounds “falsely labeled ‘for research purposes’ or ‘not for human consumption,’” and says these products were sold to consumers for human use with dosing instructions ^[1]. FDA urges people not to buy them, because they're “of unknown quality and may be harmful.”

FDA's broader warning applies too. Illegally marketed GLP-1 products may be counterfeit, may contain the wrong or harmful ingredients, or may contain too little, too much or none of the active ingredient ^[1]. A “research use only” label doesn't make a product legal for people. It means nobody has checked what's in the vial.

If you're interested in retatrutide, start with your doctor and the public trial listings

The legitimate paths are narrow but real. Trials are listed publicly on ClinicalTrials.gov, where Lilly registers its retatrutide studies along with their enrollment status and sites. A doctor can help you judge whether one fits and can ask about expanded access if you meet its strict criteria ^[3].

• Ask whether an approved drug, such as semaglutide or tirzepatide, fits your goals now.
• Ask whether you might qualify for a retatrutide trial, and what being in one involves.
• If your doctor thinks you meet the expanded-access criteria, ask them to contact the sponsor; patients can't request it themselves.
• Don't buy anything sold as retatrutide online.

Waiting is a reasonable choice too. If FDA approves retatrutide, the label will set out who it's for, the approved doses and the full list of warnings, which none of the current trial reports can do.

Retatrutide is a different molecule from Ozempic and Zepbound

Is retatrutide the same as Ozempic? No. Ozempic is semaglutide, an approved drug that acts on one receptor, GLP-1. Retatrutide is a different, unapproved molecule that acts on three. It isn't a stronger version of Ozempic, and the two can't be swapped. Zepbound and Mounjaro contain tirzepatide, which acts on two receptors, GIP and GLP-1.

If you want a GLP-1 drug now, the approved options are on our semaglutide and tirzepatide pages. Our retatrutide vs tirzepatide comparison sets the trial results side by side, with the caveats that come with comparing separate trials. For context on what pharmacies can and can't make, see whether compounded tirzepatide is still available and the compounded tirzepatide page, which covers an approved molecule, unlike retatrutide.