Retatrutide Results: What the Phase 2 Trial Reported
By DoseGauge Editorial · Updated 2026-06-12 · 4 min read
In the NEJM Phase 2 obesity trial, retatrutide produced dose-dependent weight reduction over 48 weeks. The least-squares mean change in body weight was -8.7% in the 1 mg group, -17.1% in the 4 mg group, -22.8% in the 8 mg group, and -24.2% in the 12 mg group, compared with -2.1% for placebo. Those are averages from a controlled trial of 338 adults, attributed to the published paper. They are not a prediction of what any individual will experience, and retatrutide is investigational, not FDA-approved as of June 2026.
What the Phase 2 trial measured
The trial (Jastreboff et al., NEJM 2023) was a randomized, double-blind, placebo-controlled Phase 2 study in 338 adults with obesity (a body-mass index of 30 or higher), or overweight with at least one weight-related condition, and without type 2 diabetes. Participants received subcutaneous retatrutide once weekly or placebo for 48 weeks, across target doses of 1 mg, 4 mg, 8 mg, and 12 mg, with the higher-dose arms reached by a weekly escalation.
The primary endpoint was the percentage change in body weight from baseline. The figures below are the least-squares mean changes the paper reported at week 48. "Least-squares mean" is a model-adjusted average across the group, which is how the trial summarized the result for each arm.
The weight-reduction results by dose
The table reproduces the week-48 least-squares mean change in body weight for each retatrutide group and placebo, as reported in the NEJM paper. Read each number as a group average from one controlled trial.
| Group (weekly target dose) | Mean body-weight change at 48 weeks |
|---|---|
| Placebo | -2.1% |
| Retatrutide 1 mg | -8.7% |
| Retatrutide 4 mg | -17.1% |
| Retatrutide 8 mg | -22.8% |
| Retatrutide 12 mg | -24.2% |
The pattern is dose-dependent: higher target doses corresponded to larger average reductions, and all retatrutide arms separated from placebo. The trial also reported weight reduction at the 24-week mark with the same dose-dependent shape, so the 48-week figures sit at the end of a curve that was still moving in the higher-dose arms at the time of the readout. Those are the paper's observations for this study population.
What these results do and do not mean
These are averages from a controlled 48-week trial. An average is the center of a distribution, so individual participants landed above and below each figure, and the numbers describe people enrolled under specific criteria, dosed and monitored under a protocol. A group mean from one trial is not a number any single person should expect to reproduce.
The figures also do not carry over to other settings automatically. They reflect the Phase 2 doses, duration, and population. Retatrutide is investigational and not FDA-approved as of June 2026, with Phase 3 trials (the TRIUMPH programme) ongoing and some topline data beginning to read out. Until that programme completes and a label exists, the controlling efficacy evidence is the published trial data, reported here as what the study found, not as a promise.
The calculator on this site has nothing to do with these outcomes. It converts a milligram dose into the units to draw at your reconstitution concentration. It computes reconstitution math and makes no claim about weight, results, or what any dose will do.
CalculatorOpen the Retatrutide dosage calculator ->Frequently asked questions
How much weight did people lose on retatrutide?
In the NEJM Phase 2 obesity trial, the least-squares mean weight change at 48 weeks was -8.7% (1 mg), -17.1% (4 mg), -22.8% (8 mg), and -24.2% (12 mg), versus -2.1% for placebo. These are controlled-trial group averages, not a prediction for any individual, and retatrutide remains investigational.
What was the highest weight reduction in the trial?
The 12 mg group had the largest average reduction, a least-squares mean of -24.2% of body weight at 48 weeks. That is a group average from the Phase 2 trial, not a typical or guaranteed result for any one person.
Are these results FDA-approved findings?
No. Retatrutide is not FDA-approved as of June 2026. These figures come from a published Phase 2 trial, not from an FDA label. Phase 3 (TRIUMPH) trials are ongoing, and approval would depend on that programme and a regulatory review.
Will I get the same results?
This page cannot say. The figures are averages from a controlled trial under a specific protocol and population, and individual outcomes in the trial varied around those means. Trial averages do not predict an individual result, and retatrutide is investigational. A clinician is the right person to discuss what any treatment might do for you.
Informational and educational only. Not medical advice. DoseGauge computes from the values you enter and does not recommend a dose. Talk to a licensed clinician before using any peptide or GLP-1 medication.