Realistic Weight Loss Expectations on GLP-1 Treatment

How much weight can you lose on Mounjaro? In the SURMOUNT-1 trial, adults without diabetes lost on average about 15% to 21% of their body weight over 72 weeks, depending on dose. On Wegovy 2.4 mg, the average in STEP 1 was about 15% over 68 weeks. These are averages: some people lose much more, some much less, and results in everyday care are often lower than in trials. Weight loss is usually slow at first, faster in the middle months and levels off after about a year to eighteen months. This guide sets out what the evidence shows and what affects your own results.

Why "average" matters

When you read that people lost "20%" on a medicine, it is worth knowing three things:

1. It is an average. Some people lost more than 30%, while others lost under 5%.
2. It is a percentage of starting weight. A 15% loss means 15 kg for someone starting at 100 kg, or 18 kg for someone at 120 kg.
3. It comes from a trial. Trial participants received regular support, usually reached the highest tolerated dose and were followed carefully.

Thinking in percentages helps you compare your progress fairly, whatever your starting weight.

What the main trials show

The table below summarises the main weight-management trials of medicines licensed in the UK. Trials differ in population, duration and design, so direct comparisons should be made with caution.

Head-to-head: SURMOUNT-5

SURMOUNT-5, published in 2025, directly compared tirzepatide with semaglutide in adults with obesity without diabetes. At 72 weeks, average weight loss was about 20.2% with tirzepatide and 13.7% with semaglutide. This is the most direct evidence that tirzepatide produces more weight loss on average. See our guide to SURMOUNT-5.

Wegovy 7.2 mg

In January 2026 the MHRA approved a maximum Wegovy dose of up to 7.2 mg weekly for adults with obesity (BMI of 30 or more). In the STEP UP trial, people on 7.2 mg lost nearly 21% of their body weight on average at 72 weeks, compared with about 17.5% on 2.4 mg, in an analysis of people who stayed on treatment. The higher dose doesn't apply to people with a BMI under 30 or to those using Wegovy for cardiovascular risk reduction. Check the current SmPC and speak to your prescriber.

People with type 2 diabetes

If you have type 2 diabetes, expect smaller average weight loss, though blood glucose often improves significantly. See our guide to GLP-1 medicines and type 2 diabetes.

The range of results

Trials also report what share of participants reached different thresholds. In STEP 1, about 86% of people on semaglutide lost at least 5% of their weight, around two-thirds lost at least 10%, and around a third lost at least 20%. In SURMOUNT-1, the share losing at least 5% was about 85% to 91% across tirzepatide doses, and the proportions reaching higher thresholds, such as 15% or 20%, increased with dose.

That still means around one in ten to one in seven people didn't reach 5%. If that applies to you, see our guide on what to do if GLP-1 treatment doesn't work for you.

A typical timeline

Everyone's journey is different, but trial data suggest a general pattern. Use this as a rough guide, not a target.

Short stalls of two to four weeks are common at any point. For more detail, see our Mounjaro results timeline and Wegovy results timeline.

What about weight loss per week or month?

People often ask for a weekly or monthly figure. Because loss isn't linear, an average per week can be misleading. Early weeks are slower, middle months faster and later months slower again. Focusing on the trend over three months, and on non-scale measures, tends to give a fairer picture.

Why real-world results may differ

Several factors can make results in everyday care lower than in trials:

• Dose. Trials pushed people to the highest tolerated dose. In practice, people may stay on lower doses because of cost or side effects.
• Consistency. Missed doses, gaps between prescriptions and restarting at lower doses can all reduce the effect.
• Support. Trial participants received regular lifestyle counselling.
• Health conditions and medicines. Trials exclude many people with complex health needs; some medicines make weight loss harder.
• Duration. Many people stop treatment before reaching the point at which trial results were measured.

On the other hand, some people do better than the trial average.

Factors that influence your results

Factors you may be able to influence

• Taking the medicine consistently, as prescribed, and storing it correctly
• Eating patterns, including protein, fibre and limiting liquid calories and alcohol; see our guide on what to eat on GLP-1 medication
• Physical activity, especially resistance exercise to preserve muscle
• Sleep and stress management
• Staying in touch with your prescriber, so your dose can be reviewed appropriately

Factors you may not be able to influence

• Your individual biology and genetics
• Type 2 diabetes
• Age and sex
• Some necessary medicines that promote weight gain
• Hormonal changes, such as menopause

None of this is a judgement. Two people following the same plan can have very different results.

The value of modest weight loss

Even if your results are below trial averages, they may still be worthwhile. Losing 5–10% of body weight is associated with:

• Lower blood pressure
• Improved blood glucose and lower risk of developing type 2 diabetes
• Improved cholesterol levels
• Less strain on knees and hips
• Improvements in sleep apnoea symptoms

In the SELECT trial, semaglutide reduced major cardiovascular events in people with established heart disease, and average weight loss in that trial was around 10%. Our guide to measuring progress beyond the scales explains how to track these benefits.

What about body composition?

Not all weight lost is fat. Body composition studies within STEP 1 and SURMOUNT-1 showed that most of the weight lost was fat, but a meaningful share was lean mass, which includes muscle. Prioritising protein and doing strength exercise can help preserve muscle. See our guide to preserving muscle on GLP-1 medication.

Setting realistic goals with your prescriber

When you start treatment, it can help to agree goals with your prescriber. These might include:

• A first milestone, such as 5% of starting weight after six months on an effective dose
• Health goals, such as lower blood pressure or HbA1c
• Practical goals, such as walking further or sleeping better
• A plan for what happens if progress is slower than expected

For NHS treatment, NICE (TA875 for semaglutide and TA1026 for tirzepatide) recommends reviewing treatment if less than 5% of starting weight has been lost after six months on the highest tolerated dose.

A note on cost and expectations

If you're paying privately, it is natural to want results that justify the cost. Higher doses may cost more, and prices have changed over time, including the September 2025 rise in the UK list price of Mounjaro. Factors that affect cost include the medicine, dose, and what's included in the service. We don't quote prices in guides, but you can compare services on our prices page and providers page.

For more on results, explore our results topic hub, the wider guides library, and our guide to weight loss plateaus.

Comparing your progress fairly

Use percentages, not kilograms

Two people can lose the same number of kilograms but have very different results in percentage terms. Someone starting at 90 kg who loses 9 kg has lost 10%. Someone starting at 140 kg who loses 9 kg has lost about 6.4%. Percentages make comparisons with trials, and with your own goals, much fairer.

These figures are simple arithmetic to help you translate percentages, not predictions of what you will lose.

Compare with the right trial

If you have type 2 diabetes, compare your progress with STEP 2 or SURMOUNT-2, not with STEP 1 or SURMOUNT-1. If you are on a lower dose, compare with the results for that dose. If you have been on treatment for six months, compare with where trial participants were at a similar point, not at the end of the trial.

Avoid comparing with social media

Online stories and images tend to highlight exceptional results. They may not reflect typical experiences, may not mention other treatments or circumstances, and can create unrealistic expectations. Trial data give a more balanced picture.

Myths about GLP-1 results

"Everyone loses 20%"

The 20% figure comes from the highest tirzepatide dose in SURMOUNT-1 and from SURMOUNT-5. It is an average, and many people lose less. With semaglutide 2.4 mg, the average was around 15%.

"If I haven't lost much in the first month, it won't work"

Early weeks are on low doses designed for tolerability. It is usually too early to judge. Many people who lose little at first go on to respond well once on an effective dose.

"The faster you lose weight, the better"

Very rapid weight loss can increase the risk of gallstones, muscle loss, hair thinning and nutritional problems. Steady, sustained loss on a tolerated dose is generally preferable.

"Results are permanent once achieved"

Trials such as STEP 1 extension and SURMOUNT-4 show that most people regain a substantial amount of weight after stopping. Maintaining results usually means continuing treatment or having a clear plan. See our guide to weight regain after stopping GLP-1 medication.

How expectations affect your experience

Setting realistic expectations isn't about lowering ambitions. It helps you:

• Avoid feeling disappointed during normal slow phases
• Recognise genuine progress, even when it's modest
• Have productive conversations with your prescriber about whether treatment is working
• Make informed decisions about cost, dose and duration

If your results are well below what you hoped for, that is worth discussing. Your prescriber can look at your dose, any practical issues, and other options. If your results are better than average, the focus can shift to maintaining your health and preserving muscle.

Questions to ask your prescriber at the start

• What weight loss would you consider a good response for someone like me?
• When will we review whether the treatment is working?
• What should I do if side effects make it hard to increase my dose?
• What health measures, besides weight, will we track?
• What happens when my weight loss slows or stops?
• What are the plans if I want to stop treatment in the future?

How side effects and dose shape results

Side effects and dose are closely linked to results, and both are managed by your prescriber.

Tolerability limits dose for some people

In trials, a minority of participants couldn't tolerate the highest dose and stayed on a lower one. In everyday care, nausea, vomiting, diarrhoea or constipation may mean your prescriber holds you on a dose for longer, or reduces it. This is a sensible safety decision, even if it means slower weight loss. The SURMOUNT-1 results show that lower doses still produced substantial average weight loss: around 15% at 5 mg compared with around 21% at 15 mg.

Higher doses aren't always necessary

Some people achieve good appetite control and steady weight loss on a middle dose, and never need the maximum. Others need higher doses to see a meaningful effect. Your prescriber will judge this based on your response and side effects, not on a fixed target.

Consistency over intensity

Regular, on-time doses are more important for results than reaching a particular dose quickly. Missed doses or gaps between prescriptions can mean restarting lower, with side effects returning. See our guide to Mounjaro missed doses.

Expectations for different medicines

If you are choosing between medicines with your prescriber, the evidence suggests these broad expectations:

These are trial averages, and the right medicine for you depends on your health, preferences, side effects and circumstances. Our guides to Mounjaro vs Wegovy and weight-loss injections compared go into more detail.

When to speak to a professional

Speak to your prescriber, GP or pharmacist if:

• You have been on an effective dose for several months and lost very little weight
• You are losing weight much faster than expected, or feel unwell, weak or dizzy
• You are struggling to eat enough, or are skipping meals because of side effects
• Your weight has stalled for several months and you want to discuss options
• You notice low mood, anxiety or a difficult relationship with food
• You have type 2 diabetes and your blood glucose readings change significantly

Seek urgent medical help (NHS 111, or 999 in an emergency) if you have:

• Severe, persistent abdominal pain, which may spread to your back, with or without vomiting
• Pain in the upper right abdomen with fever, or yellowing of the skin or eyes
• Repeated vomiting or diarrhoea with signs of dehydration
• Signs of a severe allergic reaction, such as swelling of the face or throat, or difficulty breathing
• A sudden change in vision