GLP-1 Statistics and Weight Loss Data (October 2026)

01 · The core data

What the main GLP-1 trials show

Trial results are the most reliable GLP-1 weight loss statistics available, because participants were measured on a set schedule against a comparison group.

Only SURMOUNT-5 supports a direct tirzepatide-versus-semaglutide comparison, because both medicines were tested in the same trial. SURMOUNT-1 and STEP 1 used different participants and designs, so their numbers should not be ranked against each other. Our GLP-1 weight loss comparison explains the differences in more depth.

02 · What next

Are these statistics relevant to you?

They are relevant if you are an adult with a BMI of 30 or more, or 27 or more with a weight-related condition, and you are considering a licensed GLP-1 treatment. A statistic cannot tell you how you will respond, so the useful next step is a conversation with a prescriber who can look at your own health history.

If you are ready to explore treatment, our GLP-1 weight loss injections service starts with a free online consultation reviewed by a GPhC-registered prescriber. For cost, the Mounjaro pen starts at £169.99 per month for the 2.5mg starter pen at the standard price, prices checked 10 October 2026.

03 · UK usage figures

What percentage of the UK is on GLP-1?

Usage is rising, but it is split between NHS prescribing and private prescribing, and private supply is not collected in a single public count.

US survey figures reflect a different health system, different prices and different prescribing rules, so they should not be read as a UK number. Survey results also depend on how the question was asked, who answered, and whether people were counting diabetes use, weight management use, or both.

On the NHS side, the picture is deliberately gradual. Mounjaro is available on the NHS, but access is being phased in over several years.⁶ NICE recommends it for adults with a BMI of at least 35 plus at least one weight-related condition, and the NHS primary-care rollout began in June 2025 with the highest-need groups first (initially BMI 40+ with four or more qualifying conditions).⁴ Full rollout is expected to take years, which is why many people who meet the licensed criteria choose regulated private treatment rather than waiting.

The same caution applies to the question of what percentage of the population is taking a GLP-1: the answer depends on the country, the year and the survey, and each source defines use differently.

04 · Semaglutide trial detail

Weight loss statistics for semaglutide and tirzepatide

Both medicines produced clinically meaningful weight loss in their trials; SURMOUNT-5 is the first large head-to-head trial of the two. In SURMOUNT-5, 751 adults took tirzepatide or semaglutide 2.4mg for 72 weeks.¹⁵ At least 10% of body weight was lost by 81.6% on tirzepatide vs 60.5% on semaglutide; at least 15% by 64.6% vs 40.1%; at least 20% by 48.4% vs 27.3%; at least 25% by 31.6% vs 16.1%.¹⁵

For semaglutide on its own, STEP 1 reported that 69.1% lost at least 10% (vs 12.0%) and 50.5% lost at least 15% (vs 4.9%).⁹ The comparison groups there received placebo, so the figures show what the medicine added.

A worked example makes percentages concrete. For someone starting at 100 kg, 20.9% is about 21 kg, which is the SURMOUNT-1 average at 15mg. Your own starting weight, dose, diet and activity will shape your own number, and trial averages do not predict your own result.²

The Wegovy dose ladder runs 0.25mg, 0.5mg, 1mg, 1.7mg and 2.4mg, stepping up after 4 weeks on each of 0.25mg, 0.5mg, 1mg and 1.7mg, so the 2.4mg maintenance dose starts from week 17.¹⁸ Mounjaro comes in six strengths from 2.5mg to 15mg.¹

05 · Side effects and stopping

Side effect statistics and coming off treatment

Side effects are part of the data, and the most common are digestive. In STEP 1, gastrointestinal side effects were reported by 74.2% of people on semaglutide 2.4mg, compared with 47.9% on placebo. 7.0% stopped treatment because of side effects, compared with 3.1% on placebo.⁹ So most people on that medicine noticed some digestive effects, while a small minority stopped because of them.

What happens when you stop? In SURMOUNT-4, people who stopped tirzepatide after 36 weeks regained on average 14% of body weight over the following year, while those who continued treatment lost a further 5.5% on average. Stopping should always be planned with your prescriber, with diet and activity habits ready to carry the load.

If you notice any new symptom, tell your prescriber and report it through the Yellow Card scheme.¹⁹

06 · Risk, regret and mood

Is a GLP-1 worth the risk? Regret and mood questions

Whether a GLP-1 is worth the risk depends on your health, your goals and the alternatives, and no statistic can decide that for you. A prescriber weighs likely benefit against side effects and your medical history, which is why these medicines are prescription-only.

Practical things that shape how people feel about treatment include whether expectations were realistic, whether side effects were managed, and whether support continued after the first order.

Regulators have looked specifically at whether GLP-1 medicines are linked to low mood or suicidal thoughts: the EMA's safety committee reviewed the evidence and concluded in 2024 that it does not support a causal link, and the MHRA keeps this under continuous review.¹⁷ That said, any big change in weight, appetite and routine can affect how you feel: tell your prescriber about any history of depression, and seek help promptly if your mood drops or you have distressing thoughts during treatment.

If you have thoughts of harming yourself or ending your life, get help straight away. Call 999 or go to A&E if you are in immediate danger. In England you can call NHS 111 and choose the mental health option, any time. You can also call Samaritans free on 116 123, day or night. Tell your prescriber about any change in your mood while taking Mounjaro.

Our GLP-1 physiology guide explains why appetite and fullness change, and the GLP-1 infographic gives a quick visual summary.

07 · Injections and tablets

Injection and tablet statistics are not interchangeable

Oral GLP-1 medicines have their own trials, and their results should not be compared with Mounjaro's as if head to head. Wegovy tablets and Foundayo each have their own licensed information.²⁰²¹ Our guide to oral GLP-1 weight loss covers what is currently licensed, and the GLP-1 medication overview sets out the oral and injection options side by side.

Liraglutide, supplied at a concentration of 6mg/ml, is a daily injection, unlike once-weekly Mounjaro and Wegovy.

If you want to see what a structured plan involves beyond the medicine, read what a GLP-1 programme involves, or visit our weight loss clinic.

08 · Serious side effects

Serious side effects: when to get help straight away

Serious side effects are uncommon but need urgent attention. Seek immediate medical help for: severe, persistent stomach pain that may spread to your back, with or without vomiting (possible pancreatitis); pain in the upper right abdomen, fever or yellowing of skin/eyes (possible gallbladder problems); or signs of a severe allergic reaction such as swelling of the face or throat and difficulty breathing. If you take insulin or a sulfonylurea alongside Mounjaro, watch for low blood sugar (shakiness, sweating, confusion) — your prescriber may need to adjust those medicines.¹