GLP1 EDUCATION

How much weight can you lose on retatrutide?

Name: How much weight can you lose on retatrutide?
Creator: Dr. Linda Moleon, MD
Published: 2026-07-19T14:14:15.062Z

Dr. Linda Moleon, MD•July 19, 2026

Key takeaways

• Retatrutide is still investigational. It has not been approved by the U.S. Food and Drug Administration and is not yet available by prescription.

• In a phase 2 trial, adults with obesity who received the highest 12-mg dose of retatrutide lost a least-squares mean of 24.2% of their body weight at 48 weeks, compared with 2.1% in the placebo group.

• In that trial, 83% of participants who received 12 mg of retatrutide achieved a weight reduction of 15% or more at 48 weeks, compared with 2% of those on placebo.

• For context, semaglutide produced a mean weight loss of 14.9% over 68 weeks in the STEP 1 trial.

• Phase 2 results are early, and effect sizes can shift once larger phase 3 trials are complete. Individual results also vary.

Dr. Linda's take

When someone asks me this question, what they usually want is a single number they can hold onto. I understand the impulse, and I also want to be careful with it, because the honest answer has more than one part.

The early data on retatrutide is genuinely striking, and I do not want to downplay that. But it is early data, from a single mid-stage study, on a medicine you cannot get today. So I hold two things at once: the results are impressive, and they are provisional. The most useful thing I can do is show you the real figures, tell you where they came from, and be clear about what is still unknown. You deserve the honest picture, not the hype version.

How much weight did people lose on retatrutide in the trial?

Most of what we know about the size of the effect comes from one study. The phase 2 trial enrolled 338 adults and ran for 48 weeks, with participants randomly assigned to receive retatrutide or placebo once weekly.

The trial's primary endpoint was the percentage change in body weight at 24 weeks, and at that point the 12-mg group had lost a mean of 17.5% compared with 1.6% on placebo. The effect kept building with time and with dose. At 48 weeks, mean weight change on retatrutide followed a clear dose-response, at 8.7% in the 1-mg group, 17.1% in the combined 4-mg group, and 22.8% in the combined 8-mg group.

At the top of that range are the numbers that got attention. In a phase 2 trial, adults with obesity who received the highest 12-mg dose of retatrutide lost a least-squares mean of 24.2% of their body weight at 48 weeks, compared with 2.1% in the placebo group.

It is not only the average that matters, but how many people reached a meaningful threshold. Every participant in the 12-mg retatrutide group achieved a weight reduction of at least 5%, and 93% achieved at least 10%, at 48 weeks. In that trial, 83% of participants who received 12 mg of retatrutide achieved a weight reduction of 15% or more at 48 weeks, compared with 2% of those on placebo.

None of this comes without trade-offs. In the trial, the most common adverse events with retatrutide were gastrointestinal, and they were dose-related and mostly mild to moderate in severity. The largest averages and the most side effects both tended to show up at the highest dose.

How does that compare to semaglutide and tirzepatide?

The two medications most people have already heard of are approved, and their trial numbers give useful context. For context, semaglutide produced a mean weight loss of 14.9% over 68 weeks in the STEP 1 trial. In the phase 3 SURMOUNT-1 trial, tirzepatide produced a mean weight loss of up to 20.9% at the 15-mg dose over 72 weeks.

These were separate trials, in different groups of people, run over different lengths of time, so the figures cannot be lined up as a head-to-head race. What you can say fairly is that retatrutide's early numbers are in the same territory as, and at the top dose numerically higher than, the approved options, without any of them having been studied directly against each other. We break down how the three stack up in retatrutide vs Zepbound vs Wegovy.

Why do these early numbers come with an asterisk?

Two reasons, and both matter.

First, this is phase 2 data. Phase 2 trials are earlier and smaller, designed mainly to find the right dose and check safety. Effect sizes seen in phase 2 do not always hold up at the same magnitude once a medicine goes through a larger, longer phase 3 program. It is common for a top-line number to move as the research matures.

Second, the biggest averages came from the highest dose, and the highest dose also drove the most side effects. A number pulled from one end of a dose range is not the number an average person would necessarily see. If you want the plain-language overview of how this medicine works and where it sits in development, we cover it in what is retatrutide.

What does investigational mean for you right now?

Investigational has a specific meaning. Retatrutide is not approved by the FDA, which means it has not cleared the review that confirms a medicine's benefits outweigh its risks for general use. It is not something a clinician can prescribe, and it is not available at a pharmacy.

In practical terms, the honest answer is that no individual can be promised a specific result, because trial averages describe groups rather than any one person, and because this medicine is not an option today regardless. If you are weighing your choices among approaches that are actually available now, our eligibility quiz is a good starting point.

Frequently asked questions

Is retatrutide approved by the FDA?

No. Retatrutide is still investigational, and it is not approved by the FDA or available by prescription as of now.