How fast do people lose weight on semaglutide and tirzepatide

In the major trials, weight loss on semaglutide and tirzepatide was gradual: modest in the first couple of months while the dose was still low, steadier once people reached a full dose, and leveling off somewhere between about 12 and 18 months. Averages across thousands of participants hide a wide spread, though, and your own pace may look quite different.

This article covers timing. If you want the basics of how these drugs work, start with our guide to GLP-1 medications. The question of which drug to choose is covered in semaglutide vs tirzepatide.

What the trials actually measured

The numbers most often quoted come from two trial programs: STEP for semaglutide (sold as Wegovy for weight management) and SURMOUNT for tirzepatide (sold as Zepbound). Both enrolled adults with obesity, or with overweight plus at least one weight-related condition, and both paired the drug with lifestyle counseling. The placebo groups got the same counseling, which is why they lost a little weight too.

Two details matter when you read these results. First, the headline figures are averages at the end of the trial, after more than a year. Second, the published results are reported in more than one way. The "treatment-regimen" figure includes everyone who was randomized, including people who stopped the drug. The "efficacy" or "on-treatment" figure only looks at people who kept taking it, and it is higher. When you see different percentages quoted for the same trial, that is usually why.

STEP-1: semaglutide 2.4 mg

STEP-1 followed 1,961 adults for 68 weeks. The average weight loss on semaglutide was 14.9%, compared with 2.4% on placebo. About 86% of people on semaglutide lost at least 5% of their body weight, and about half lost at least 15%. The weight curve kept falling for most of the trial and flattened in its final months.

SURMOUNT-1: tirzepatide

SURMOUNT-1 followed 2,539 adults for 72 weeks at three maintenance doses. Average weight loss was 15.0% at 5 mg, 19.5% at 10 mg and 20.9% at 15 mg, compared with 3.1% on placebo. As with semaglutide, the curve was steep in the middle months and flattened toward the end.

Higher-dose semaglutide

The FDA approved a 7.2 mg dose of semaglutide (Wegovy HD) in March 2026 based on the STEP UP trials. In STEP UP, adults without diabetes on 7.2 mg lost about 19% on the treatment-regimen measure over 72 weeks, compared with roughly 4% on placebo. Higher doses also bring more gastrointestinal side effects for many people.

What the first months tend to look like

Both drugs start at a low dose and step up every 4 weeks or so. That schedule exists to limit nausea and other side effects, and it means you spend the first few months on doses below the ones studied for long-term weight loss. Our article on how GLP-1 dosing and titration work explains the steps.

A rough way to think about it, drawn from the shape of the trial curves rather than a promise:

• Weeks 1 to 4. Many people notice a change in appetite and food noise before they see much change on the scale. Some of the early drop can be water and reduced food volume.
• Months 2 to 4. As the dose increases, weight loss usually becomes more consistent. The STEP-4 trial gives a useful snapshot: during its 20-week lead-in, when everyone was stepped up to semaglutide 2.4 mg, participants lost an average of 10.6%.
• Months 4 to 12. On a full maintenance dose, this is typically when the largest share of loss happened in the trials. In SURMOUNT-4, people on tirzepatide lost an average of 20.9% over a 36-week lead-in period.
• Months 12 to 18. Loss slows. The body adapts, and most people reach a new, lower plateau.

Why the pace varies so much

Within every trial arm, the range was wide. Some people lost more than a quarter of their body weight; a minority lost less than 5%. Factors linked to the difference include:

• Type 2 diabetes. People with diabetes lost less on average in both programs. In STEP-2, which enrolled adults with type 2 diabetes, average loss on semaglutide 2.4 mg was 9.6% over 68 weeks.
• Dose reached. Side effects keep some people on lower doses, and lower doses produced less loss on average.
• Sex and starting weight. Women lost a higher percentage on average in several analyses. Starting weight affects how pounds translate into percentages.
• Other medications. Some drugs, including certain antidepressants, antipsychotics, steroids and insulin, are associated with weight gain and can work against the effect.
• Sleep, stress and activity. These affect appetite and energy balance for everyone, on or off medication.
• Consistency. Missed doses or gaps between fills can mean restarting at a lower dose.

Faster is not necessarily better

It is common to want quick results, but faster loss is not always the goal. Rapid weight loss can increase the risk of gallstones, which appear in the prescribing information for both drugs, and may mean more lean mass is lost along with fat. Our article on muscle loss on a GLP-1 covers how protein and resistance training help.

Pushing up the dose sooner than your prescriber recommends usually just means more nausea, vomiting or constipation. It does not reliably speed up results, and severe vomiting can lead to dehydration.

When to ask whether it is working

Many obesity medicine clinicians reassess after a few months on the maintenance dose. A commonly used benchmark is whether someone has lost at least 5% of body weight after about 12 to 16 weeks on a full dose. If not, a clinician may discuss a dose change, a switch to a different drug, or stopping. A slowdown later on is a different matter; it is covered in our piece on the weight loss plateau.

Weight is also not the only measure that matters. Blood pressure, blood sugar, cholesterol, sleep apnea symptoms and how you feel day to day are part of the picture, and they can improve before the scale moves much.

A clinician can review your history, medications and goals and tell you what a reasonable expectation looks like for you. Our weight management program explains how that evaluation works. No one can promise a specific amount of weight loss, and a clinician may decide that a GLP-1 isn't right for you.

Questions patients ask us

How much weight did people lose on semaglutide in the STEP-1 trial?

In STEP-1, published in NEJM in 2021, adults without diabetes on semaglutide 2.4 mg lost an average of 14.9% of their body weight over 68 weeks, compared with 2.4% on placebo. About half lost at least 15%. Those are averages from a trial with lifestyle counseling, and individual results ranged widely in both directions.

How much weight did people lose on tirzepatide in SURMOUNT-1?

In SURMOUNT-1, published in NEJM in 2022, adults on tirzepatide lost an average of 15.0% at 5 mg, 19.5% at 10 mg and 20.9% at 15 mg over 72 weeks, compared with 3.1% on placebo. As with semaglutide, these are group averages; some participants lost much more and some much less.

Why am I not losing much weight in the first month?

The first month is usually spent on the lowest dose, which is meant for tolerance rather than weight loss. Many people notice appetite changes before the scale moves. In the trials, loss became steadier as doses rose over the first few months. Slow early progress is common and not a sign the drug will not work.

When does weight loss on a GLP-1 usually level off?

In the STEP-1 and SURMOUNT-1 trials, average weight curves flattened toward the end of the first year to year and a half of treatment. The body adapts to a lower weight and a new plateau forms. That is expected. A plateau in the first months is different and worth discussing with your clinician.

Do people with diabetes lose less weight on GLP-1s?

On average, yes. In STEP-2, adults with type 2 diabetes on semaglutide 2.4 mg lost an average of 9.6% over 68 weeks, less than in STEP-1. Similar patterns appeared with tirzepatide. Blood sugar and other health measures often improve meaningfully even when weight loss is more modest.

Is losing weight faster on a GLP-1 better?

Not necessarily. Rapid weight loss is linked to a higher risk of gallstones, which appear in both drugs' prescribing information, and may mean more muscle is lost along with fat. Pushing doses up faster than prescribed usually brings more side effects without reliably faster results. A steady pace with enough protein and strength training is generally the aim.

What is the difference between the treatment-regimen and efficacy results in trials?

The treatment-regimen figure includes everyone randomized, even people who stopped the drug. The efficacy, or on-treatment, figure includes only people who kept taking it as planned, so it is higher. Both are legitimate, but they answer different questions. When you see two numbers for the same trial, this is usually why.

How do I know if my GLP-1 is working?

Many clinicians use a benchmark of at least 5% weight loss after roughly 12 to 16 weeks on a full maintenance dose. If you are below that, options include a dose change, a different drug, or stopping. Improvements in blood pressure, blood sugar, cholesterol and how you feel day to day also count.

Will higher-dose Wegovy make me lose weight faster?

In the STEP UP trial behind the 7.2 mg Wegovy approval in March 2026, average loss was about 19% over 72 weeks on the treatment-regimen measure, higher than with 2.4 mg in earlier trials. It also brought more side effects. It is an option for some adults after time on lower doses, not a starting point.

Can my other medications slow weight loss on a GLP-1?

They can. Some antidepressants, antipsychotics, steroids, certain diabetes drugs including insulin, and some seizure medications are associated with weight gain and may work against a GLP-1. Do not stop any medication on your own. Bring a full list to your evaluation so your clinician can consider alternatives where appropriate.