Retatrutide weight loss: the results from every trial so far

Retatrutide weight loss is the reason this drug gets so much attention. In Lilly's largest obesity trial, adults on the top dose lost a quarter of their body weight on average over 80 weeks. But retatrutide is not approved by the FDA or any other regulator [Lilly, Oct 28, 2026]. Every number below comes from a clinical trial, and each one is only as good as the trial behind it.

So this page gives each result with its trial, dose, length and placebo figure. It also says who reported it: a peer-reviewed journal, or only a Lilly press release. If you're new to the drug, start with what retatrutide is.

How much weight did people lose on retatrutide?

Five peer-reviewed papers from Lilly's phase 3 retatrutide studies report weight results. The table uses the figure each paper leads with, which counts everyone who was assigned to a group. That includes people who stopped taking the drug early.

Each of these trials was double-blind and placebo-controlled, and each was funded by Lilly [Diabetes Obes Metab, 2025] [Lancet, Jun 6, 2026]. People also followed a healthy diet and physical activity alongside the drug or placebo [Diabetes Obes Metab, 2025]. That's why the placebo groups lost some weight too.

Two trials are missing from this table because no paper exists yet. In TRIUMPH-3, 1,949 adults with severe obesity and heart disease (Lilly's count) took 9 mg, 12 mg or placebo for 80 weeks [Lilly, Jul 23, 2026]. In TRANSCEND-T2D-2, 1,298 adults with type 2 diabetes took retatrutide or Ozempic 2 mg for 80 weeks, and everyone knew which drug they had [Lilly, Oct 28, 2026]. Lilly has released only one kind of figure for each, which is explained next.

Why do you see two numbers for each trial?

Lilly's press releases lead with a figure it calls the "efficacy estimand." Lilly defines it as the result had all randomized participants remained on study intervention [Lilly, May 21, 2026]. In plain words, it estimates what would happen if nobody quit. The journal papers lead with the "treatment-regimen estimand," which counts everyone, whether they stayed on the drug or not [NEJM, Sep 29, 2026].

Both are correct answers to different questions. The efficacy number is always the larger one. The treatment-regimen number is closer to what a group of real patients might see, so this site leads with it. Here are Lilly's figures, kept in their own table so the two kinds never mix:

On the same basis, 65.3% of people on 12 mg in TRIUMPH-1 ended the trial with a BMI under 30, below the cutoff for obesity [Lilly, May 21, 2026]. Lilly also reported that 33.3% reached a BMI under 25 [Lilly, Jun 6, 2026].

How fast did the weight come off?

The clearest timeline comes from the phase 2 trial. On 12 mg, average weight loss was 17.5% at 24 weeks and 24.2% at 48 weeks, compared with 1.6% and 2.1% on placebo [NEJM, 2023]. These are efficacy-estimand figures, per Lilly's footnote [Lilly, Jun 26, 2023]. The trial's lead investigator said people had not yet reached a weight plateau at the time the study ended [Lilly, Jun 26, 2023].

Many people search for "retatrutide weight loss per week." Here is the simple arithmetic, which is ours and not a trial result. On 12 mg in phase 2, the first 24 weeks averaged about 0.7 percentage points a week. The next 24 weeks averaged about 0.3 a week.

So a single weekly figure hides a curve that starts fast and then slows. It also ignores the start. In the phase 3 trials, the dose was raised step by step over the first 16 weeks before people reached 12 mg [Diabetes Obes Metab, 2025]. Our retatrutide dosage guide lists the doses each trial tested.

Longer results come only from Lilly so far. TRIUMPH-1 had an extension to 104 weeks. People first assigned to 12 mg, then kept on their highest tolerated dose of 9 or 12 mg, lost 29.9% on the count-everyone basis [Lilly, May 21, 2026]. That group was selected, though: 532 people with a BMI of 35 or more who finished 80 weeks and tolerated their dose [Lilly, May 21, 2026]. It says little about everyone who starts the drug.

Who lost less weight?

People with type 2 diabetes lost less. On 12 mg over 80 weeks, the average was 18.8% in TRIUMPH-2, against 25.0% in TRIUMPH-1, whose participants did not have diabetes [Lancet, Sep 29, 2026] [NEJM, Sep 29, 2026]. Lilly calls this a population with increased difficulties losing weight [Lilly, Jul 23, 2026]. Tirzepatide showed the same pattern in its own trials: 14.7% on 15 mg over 72 weeks with type 2 diabetes, against 20.9% without [FDA label, Aug 2026].

Lower doses gave smaller results. In TRIUMPH-1, 4 mg produced 17.6% over 80 weeks, compared with 25.0% on 12 mg [NEJM, Sep 29, 2026]. Higher doses also led more people to stop because of side effects: 11.3% on 12 mg, compared with 4.1% on 4 mg and 4.9% on placebo [Lilly, May 21, 2026]. The retatrutide side effects guide has the full figures.

What about women and men? The trials enrolled both, and the TRIUMPH trials assigned groups with sex as a balancing factor [Diabetes Obes Metab, 2025]. But no source we checked reports weight results for women and men separately. The retatrutide benefits guide covers what is and isn't known beyond the scale.

What happens when you stop retatrutide?

Nobody has published a clear answer yet. The only data come from a small phase 2 liver substudy. Its authors wrote: Some weight regain was observed at the safety follow-up visit 4 weeks after discontinuation of treatment [Nature Medicine, 2024]. Four weeks is far too short to show the long-term pattern.

A proper test is running. TRIUMPH-6 gives everyone retatrutide for 80 weeks, then switches some people to placebo for 36 weeks while others stay on the drug [ClinicalTrials.gov, NCT06859268]. The registry estimates its main data collection ends in April 2028 [ClinicalTrials.gov, NCT06859268].

For a sense of what such trials can show, look at a different drug. When people who had taken tirzepatide (Zepbound) for 36 weeks switched to placebo, their weight went back up by 14.0% over the next 52 weeks. People who stayed on tirzepatide lost a further 5.5% [FDA label, Aug 2026]. That's tirzepatide, not retatrutide, so treat it only as context.

What about retatrutide reviews and before-and-after photos?

Online reviews and before-and-after photos can't do what a trial does. A trial weighs everyone, including people who gained weight, felt sick or quit. A photo shows one person, chosen by whoever posted it, with no record of dose, diet or what happened a year later.

There is also the question of what was injected. No one can legally sell retatrutide for human use [Lilly, Oct 2026], so most people posting about it are using products of unknown origin. Lilly warns these products may contain unknown ingredients, harmful contaminants and impurities and may hold too much, too little or the wrong active ingredient [Lilly, Oct 2026]. The FDA has warned sellers that label such products for research purposes [FDA, Oct 1, 2026]. Our guide to retatrutide for sale online explains what those listings are.

One peer-reviewed study has looked at user reports. Researchers analyzed Reddit posts from 13,589 people describing retatrutide use from March 2023 through December 2025 [JAMA Netw Open, Oct 2026]. They studied side effects, not weight. And they were blunt about the limits: Product identity, purity, dose, route, treatment duration, concomitant medications, and medical history cannot be verified. [JAMA Netw Open, Oct 2026] The most common complaint, increased appetite in 17.1% of the 7,823 users with a mapped symptom, surprised the authors given the trial results [JAMA Netw Open, Oct 2026].

How do these results compare with approved drugs?

Here are the closest like-for-like figures, all counting everyone assigned. Retatrutide 12 mg: 25.0% over 80 weeks in TRIUMPH-1, compared with 3.9% on placebo [NEJM, Sep 29, 2026]. Tirzepatide 15 mg: 20.9% over 72 weeks in SURMOUNT-1, compared with 3.1% [NEJM, 2022]. Semaglutide 2.4 mg: 14.9% over 68 weeks in STEP 1, compared with 2.4% [NEJM, 2021].

These trials differed in length, timing and the people they enrolled, and no head-to-head result against tirzepatide exists. That trial, TRIUMPH-5, has not reported [ClinicalTrials.gov, NCT06662383]. The one head-to-head trial so far, against Ozempic in type 2 diabetes, is still a press release [Lilly, Oct 28, 2026]. See retatrutide vs tirzepatide and retatrutide vs semaglutide for the full comparisons.

The bottom line is simple. The trial numbers are large and consistent across five peer-reviewed papers. But they describe people on Lilly's trial drug, under medical supervision, and not anyone using a product bought online.