GuideGLP-1 Average Weight Loss per Week: What Trials Show

By Dosinha Team | Updated 2026-10-06 | 8 min read

This article is for information only and is not medical advice. Talk to your prescriber or a qualified professional.

There is no official GLP-1 average weight loss per week. Trials report total change at the end, usually after 68 or 72 weeks. In STEP 1, adults without diabetes on semaglutide 2.4 mg lost a mean 15.3 kg (about 34 lb) over 68 weeks. Spread evenly, that is about 0.2 kg (0.5 lb) a week. But weight did not come off evenly: it fell fastest in the first months and leveled off after about a year. These are group averages from studies, not a prediction for you, and no medicine guarantees any amount of weight loss.

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Key points

• Trials report the mean change at the end of treatment, not a weekly rate. Dividing the total by the number of weeks gives a rough average only.
• In the main trials in adults without diabetes, mean weight change was 14.9% at 68 weeks with semaglutide 2.4 mg and 15.0% to 20.9% at 72 weeks with tirzepatide, depending on dose.
• Loss was faster in the first 6 months and then slowed, with a plateau after roughly 60 weeks in the semaglutide trials.
• Individual results varied widely around those averages, in both directions.

What the trials actually measured

The two trials most people mean when they talk about GLP-1 weight loss are STEP 1 (semaglutide, the ingredient in Wegovy) and SURMOUNT-1 (tirzepatide, the ingredient in Zepbound). Both enrolled adults with a BMI of 30 or more, or 27 or more with at least one weight-related condition, and both excluded people with diabetes. Everyone also got lifestyle support. In the Wegovy trials, the label describes a reduced-calorie diet of about 500 kcal a day below usual intake and at least 150 minutes of activity a week.

In STEP 1 the mean change was 15.3 kg on semaglutide and 2.6 kg on placebo. About 86% of people on semaglutide lost at least 5% of their weight, 69% lost at least 10%, and about half lost at least 15%. In SURMOUNT-1, 85% to 91% of people on tirzepatide lost at least 5%, depending on dose. Mean starting weight was about 105 kg (231 lb).

These are different trials, so treat the table as a sense of scale, not a head-to-head comparison.

Turning trial totals into a weekly or monthly number

Here is the simple arithmetic. It is our division of published averages, not a number any trial reported.

• STEP 1: 14.9% over 68 weeks is about 0.2% of starting weight per week. In kilograms, 15.3 kg over 68 weeks is about 0.2 kg (0.5 lb) a week, or roughly 1 kg (2 lb) a month.
• SURMOUNT-1, 15 mg: 20.9% over 72 weeks is about 0.3% of starting weight per week.
• SURMOUNT-1, 5 mg: 15.0% over 72 weeks is about 0.2% per week.

Nobody in these trials lost weight at a steady weekly rate. The next section explains why that average hides the real shape of the curve.

The shape of the curve: fast early, then flatter

The 2025 joint nutrition advisory on GLP-1 therapy, led by Mozaffarian, sums up the pattern: weight loss is generally faster during the first 6 months, slows after that, and reaches a relative plateau at around 18 months. When the medicine is continued, the loss has been sustained for at least 4 years in controlled and observational studies.

The trials show the same shape at specific points:

• Week 20 (semaglutide): in STEP 4, 902 adults without diabetes started semaglutide. The 803 who reached the 2.4 mg dose by week 20 had lost a mean 10.6% by then. Those weeks included 16 weeks of dose escalation.
• Around week 60 (semaglutide): the STEP 5 authors report that weight loss plateaued after approximately week 60 and was then maintained. They note the same plateau around week 60 in the earlier 68-week trials.
• Week 104 (semaglutide): in STEP 5, 304 adults without diabetes had a mean change of 15.2% on semaglutide versus 2.6% on placebo after two years.

So a person’s weekly loss in the early months may look much faster than 0.5 lb, and later months may show little change at all. Both fit the same average curve. See plateau on GLP-1 for the flatter part.

The first month

The trials we read do not report a first-month average, so we will not give one. The labels do say treatment starts low. According to the Wegovy and Zepbound prescribing information, the first 4 weeks use a starting dose, and the dose is then raised step by step to reduce stomach side effects. The Zepbound label states that its 2.5 mg starting dose is for treatment initiation and is not a maintenance dose. Your prescriber and pharmacist set your plan. For how the steps work in the label, see GLP-1 dosage: what the labels say.

Why your number may look different

• Averages hide a wide spread. In STEP 1, about 14% of people on semaglutide lost less than 5%, while about half lost 15% or more. One person’s before and after photo tells you even less, which is why we do not publish them.
• Diabetes changes the picture. In the Wegovy label’s trial of adults with type 2 diabetes, mean change at 68 weeks was 9.6% versus 3.4% on placebo, lower than in people without diabetes. More in GLP-1 weight loss without diabetes.
• Dose and medicine matter. The trial figures are for semaglutide 2.4 mg and tirzepatide 5, 10 and 15 mg. Ozempic and Mounjaro are approved for type 2 diabetes, with their own doses, so these numbers are not a statement about them.
• Time on treatment matters. Most of the published averages come after more than a year of treatment. How long people take a GLP-1 covers what labels and withdrawal trials say.

Faster is not always better

The Wegovy prescribing information notes that substantial or rapid weight loss can increase the risk of gallstones, and both the Wegovy and Zepbound labels list acute gallbladder disease as a warning. The 2025 advisory also highlights muscle and bone loss as a concern during weight loss and points to resistance training and enough protein. See GLP-1 muscle loss and protein on a GLP-1.

Related guides in this series

• GLP-1 weight loss without diabetes
• How long do you take a GLP-1 for weight loss
• Plateau on GLP-1
• What happens when you stop a GLP-1

When to call a clinician

Talk to your prescriber if your weight is changing much faster or slower than you were told to expect, or if you are not able to eat or drink enough. From the Wegovy Medication Guide and the Zepbound label:

When to call: severe stomach pain that will not go away, with or without vomiting, sometimes spreading to the back (possible pancreatitis). Pain in the upper stomach, yellowing of the skin or eyes, fever or clay-colored stools (possible gallbladder problems). Nausea, vomiting or diarrhea that does not go away, which can lead to dehydration and kidney problems. Swelling of the face, lips, tongue or throat, or trouble breathing or swallowing: get medical help right away.

This list is not complete. When something feels wrong, call your prescriber, a pharmacist or local emergency services.

Frequently asked questions

How much weight do you lose per week on a GLP-1?

Trials do not report a weekly rate. Dividing STEP 1’s 68-week result gives about 0.2 kg (0.5 lb) a week on semaglutide 2.4 mg, but loss was faster early and slower later. Your own pace can differ a lot from that average.

What is the average weight loss per month on a GLP-1?

Spread evenly, STEP 1’s mean of 15.3 kg over 68 weeks is roughly 1 kg (about 2 lb) a month. That is arithmetic on a group average, not a monthly rate anyone was promised or measured.

How quickly do you lose weight on a GLP-1?

In the semaglutide trials, the fastest change came in the first months. People who reached the full dose in STEP 4 had lost a mean 10.6% by week 20. Weight then leveled off after about 60 weeks.

How long does it take to lose weight on a GLP-1?

The main trial results come after 68 to 72 weeks. The 2025 nutrition advisory describes a relative plateau at around 18 months, with results sustained for years when treatment continues. Your prescriber can tell you what to expect for you.

Keep your own record

A steady weight log makes the trend easier to see than any single weigh-in. Dosinha’s free weight log, shot log and side-effect check-ins help you keep that record and notice patterns to share with your prescriber. The app does not cause or predict weight loss, and it does not tell you what to do about your medicine. Try the free tools.

Sources

• Wilding JPH, et al. Once-weekly semaglutide in adults with overweight or obesity (STEP 1). New England Journal of Medicine, 2021.
• Jastreboff AM, et al. Tirzepatide once weekly for the treatment of obesity (SURMOUNT-1). New England Journal of Medicine, 2022.
• Rubino D, et al. Effect of continued weekly subcutaneous semaglutide vs placebo on weight loss maintenance (STEP 4). JAMA, 2021.
• Garvey WT, et al. Two-year effects of semaglutide in adults with overweight or obesity: the STEP 5 trial. Nature Medicine, 2022.
• Mozaffarian D, et al. Nutritional priorities to support GLP-1 therapy for obesity: a joint advisory. Obesity, 2025.
• DailyMed. Wegovy prescribing information and Zepbound prescribing information. Labels posted 2026.

This article is for information only and is not medical advice. Talk to your prescriber or a qualified professional.