SURPASS-2: Tirzepatide vs Semaglutide Results (October 2026)

01 · The short verdict

SURPASS-2 verdict: what it tells you and what it does not

SURPASS-2 tested tirzepatide against once-weekly semaglutide in people with type 2 diabetes, and its primary focus was blood sugar control³. It is the trial most often quoted when people ask whether tirzepatide beats semaglutide. Its population, though, is people with diabetes, not adults seeking weight management.

The full HbA1c changes by dose, the weight change and the secondary outcomes are in the NEJM paper (source 3). For a plain-English walk-through of the trial, see our SURPASS-2 overview.

If your goal is weight loss, a better question is what the head-to-head weight-management trial found.

02 · Side by side

Tirzepatide vs semaglutide: the evidence

The trials differ in population, length and dose, so only SURMOUNT-5 supports a direct comparison. Do not read down the columns as a head-to-head.

You can see the current Mounjaro costs on the Mounjaro pen page and the Wegovy pen page.

03 · Choosing

Who each option suits

Both are effective, licensed treatments, and the headline number alone should not decide it¹⁵. Mounjaro is licensed for weight management in adults and for type 2 diabetes¹. In SURMOUNT-5, tirzepatide's average weight loss was higher than semaglutide 2.4mg's¹⁵.

A prescriber may still choose semaglutide. Reasons include your medical history, how you have tolerated other medicines, or what you have already tried. That is a clinical judgement, not a ranking. Our tirzepatide vs semaglutide guide goes through the practical differences, and our weight-loss comparison focuses on the obesity evidence.

04 · SURMOUNT-5 head-to-head

SURMOUNT-5: the weight-loss head-to-head

SURMOUNT-5 is the first large head-to-head trial of tirzepatide against semaglutide for weight loss. Adults on tirzepatide lost on average 20.2% of body weight over 72 weeks, versus 13.7% on semaglutide 2.4mg (Wegovy)¹⁵. These are trial averages, and individual results vary.

As a worked example only, for someone starting at 100 kg, 20.2% is about 20 kg and 13.7% is about 14 kg. Your own result depends on dose, diet, activity and how you tolerate treatment.

Each medicine also has its own pivotal trial. In SURMOUNT-1, tirzepatide produced average losses of 15% on 5mg, 19.5% on 10mg and 20.9% on 15mg over 72 weeks, versus 3.1% with lifestyle changes alone². In STEP 1, semaglutide 2.4mg produced 14.9% over 68 weeks versus 2.4% on placebo⁹. Those two trials ran separately, so they should not be set against each other as a head-to-head. Only SURMOUNT-5 does that. More detail is in our SURMOUNT-5 results page and our guide to weight-loss superiority.

05 · HbA1c and hsCRP

HbA1c, body weight and hsCRP in SURPASS-2

HbA1c reflects average blood sugar over recent months and was the central measure in a diabetes trial like this. hsCRP is a blood marker of inflammation that researchers sometimes examine in secondary analyses.

For dose-by-dose figures, the NEJM paper is the place to read them.

If you have type 2 diabetes, the right treatment and target for you belong to your diabetes team. NICE has issued separate guidance on tirzepatide for type 2 diabetes⁸. Do not start or change any diabetes treatment without talking to your diabetes team.

06 · Side effects compared

Side effects: what the evidence says

Most tirzepatide side effects are digestive. The most common, affecting more than 1 in 10 people, are nausea, diarrhoea, vomiting, constipation and abdominal discomfort¹. Common effects, up to 1 in 10 people, include indigestion, reduced appetite, dizziness, reflux, burping, hair shedding and injection-site reactions¹.

In the weight-management trials, nausea was reported by 24.6% of people on 5mg, 29.0% on 10mg and 28.0% on 15mg, versus 8.5% on placebo. Diarrhoea was reported by 18.7%, 20.8% and 22.5% respectively, versus 7.8% on placebo¹. These effects were more common while the dose was being increased and became less frequent over time. Treatment was stopped permanently because of gastrointestinal effects by 1.9% on 5mg, 3.3% on 10mg and 4.3% on 15mg, versus 0.5% on placebo¹.

Which GLP-1 has the fewest side effects for you depends on the person and the dose. Our page on side effects by dosage goes further, and the meta-analysis comparison looks at pooled evidence.

07 · Managing effects

Managing side effects and knowing when to seek help

Side effects are most likely when you start or move up a dose, and for most people they ease within days to a few weeks¹. This is one reason Mounjaro uses a gradual dose ladder. Everyone starts on 2.5mg weekly, and after at least 4 weeks the dose steps up to 5mg, then by 2.5mg at no less than 4-week intervals to a maximum of 15mg¹.

Practical steps that help most people include eating smaller meals slowly, stopping at the first feeling of fullness, favouring plain lower-fat foods while adjusting, staying hydrated and avoiding lying down straight after eating¹³. If vomiting is persistent or you cannot keep fluids down, contact your clinical team — dehydration needs medical 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 the skin or eyes (possible gallbladder problems); or signs of a severe allergic reaction such as swelling of the face or throat and difficulty breathing¹³. If you take insulin or a sulfonylurea, watch for low blood sugar, because those doses may need adjusting¹³. You can report any suspected side effect through the Yellow Card scheme.

08 · Getting it in the UK

Getting tirzepatide in the UK

Mounjaro is available on the NHS, but access is being phased in over several years. NICE recommends it for adults with a BMI of at least 35 plus at least one weight-related condition, and the primary-care rollout began in June 2025 with the highest-need groups first⁴⁶. Full rollout is expected to take years, so many people who meet the licensed criteria choose regulated private treatment instead.

With us, the process starts with a free online consultation, and a GPhC-registered prescriber reviews it. Payment is taken when you place the order; if the prescriber decides the treatment is not suitable, the order is refunded automatically in full. Approved orders are dispensed by our registered pharmacy, with same-day dispatch when ordered by 3pm and free next-day tracked delivery. When you are ready, start your free consultation or browse all weight loss treatments.

Mounjaro is a prescription-only medicine, used alongside a reduced-calorie diet and increased physical activity. Individual results vary. This page is information, not a substitute for medical advice.