GLP-1 Weight Loss Plateau: What the Trials Show

Last updated October 20, 2026

Short answer: Slowing down is the normal pattern, not a sign the medication stopped working. In an analysis of the SURMOUNT-1 tirzepatide trial, the median person reached a weight plateau (less than 5% change over 12 weeks) at roughly 24 to 36 weeks, depending on starting BMI, and about 88% to 90% of people who lost at least 5% had plateaued by week 72. Higher doses, younger age and female sex were linked to plateauing later.

What a plateau means in the trial data

There is no accepted medical definition of a weight plateau. The analysis cited here, co-authored by Eli Lilly employees and academic researchers, defined it as a weight change of less than 5% over a 12-week period and every 12-week period after that. That is a fairly loose bar, so a plateau in this sense can still include slow, steady loss.

The analysis covered 1,438 people in SURMOUNT-1 who received at least 75% of their doses and lost at least 5% of their weight. It was a post hoc, exploratory analysis, so the findings are not firm rules.

How long it took to plateau

Among the people with higher starting BMI, plateaus came later and the total loss from week 24 to week 72 was larger: an additional 4.6% for the overweight group versus 7.0%, 8.8% and 9.7% for classes 1, 2 and 3. About 12% of people in the longer SURMOUNT-4 trial had not plateaued by the end of the study.

Who plateaued later

• People on higher doses. The plateau came on average 4.4 weeks later on 10 mg and 6.7 weeks later on 15 mg than on 5 mg.
• Younger people: about 0.9 weeks later for every 10 years younger.
• Women: about 4.2 weeks later than men.

This analysis looked only at tirzepatide, and only at people who stayed on treatment and lost at least 5%. It does not tell you how long someone who responds poorly or stops early would take.

The shape of the curve in our model

Our calculator uses the same general idea: fast early loss that slows as it approaches the trial average. For illustration, this is the share of the eventual trial-average loss that the model places at each point. It is a smoothed average, not a prediction for any one person.

Read the details in how the calculator works, or see how long results take.

If your weight has stopped moving

We cannot tell you why a particular plateau happened, and the analysis above did not measure food intake or activity. A few things are worth raising with your prescriber:

• Whether you are at your full maintenance dose. Both labels build dose up in steps, and the trial results are measured after that point. See our dosage charts for the schedules.
• Whether side effects or low appetite have changed how much you are eating. Our protein and nausea guides cover what the advisory recommends.
• Whether you are doing strength training, which the 2025 advisory recommends at least three times a week.
• Whether the plateau is where you hoped to be. In the trials, continuing tirzepatide kept weight down and even lowered it further, while stopping led to regain. See what happens when you stop.

Related reading: what happens when you stop, protein on a GLP-1 and muscle loss.