Mounjaro vs Wegovy in the UK

The two leading weight-management injections compared factually: what they are, who they are licensed for, what the trials showed, and what each costs from regulated UK providers today. This page informs a conversation with a prescriber; it does not choose a medicine for you.

About this page. Written by the GLPInfo editorial team with AI assistance from the official sources listed at the end, and approved by the site owner before publication. It has not been reviewed by a named clinician. Published 18 Aug 2026 · last updated 18 Aug 2026 · next scheduled review 18 Nov 2026. What changed: first publication.

This page is information, not medical advice. It never tells you which medicine, dose or format is right for you: those decisions sit with you and a qualified prescriber. Spotted an error? Tell us and we'll fix it fast.

What they are and how they work

Mounjaro (tirzepatide, Eli Lilly) is a once-weekly injection that activates both the GIP and GLP-1 receptors. Wegovy (semaglutide, Novo Nordisk) is a once-weekly injection that activates the GLP-1 receptor. Both mimic gut hormones released after eating: they slow stomach emptying, act on appetite centres in the brain and increase the feeling of fullness, which reduces how much people eat. Both are used alongside a reduced-calorie diet and increased physical activity, not instead of them.

UK licence and eligibility

Both are MHRA-licensed for weight management in adults with a BMI of 30 or more (obesity), or from 27 with at least one weight-related condition such as type 2 diabetes, high blood pressure or obstructive sleep apnoea. Tirzepatide is also licensed separately for type 2 diabetes. These are prescription-only medicines: whether either is appropriate, and at what dose, is always decided by a qualified prescriber after an individual assessment, whether through the NHS or a regulated private provider. No comparison site, including this one, can tell you whether you are eligible.

Dosing and escalation

Both start low and step up to limit side effects. Mounjaro starts at 2.5mg weekly and can increase every four weeks through 5, 7.5, 10 and 12.5 up to 15mg. Wegovy starts at 0.25mg weekly and steps through 0.5, 1 and 1.7 up to the 2.4mg maintenance dose over about 16 weeks. The step-ups matter financially as well as clinically, because most providers price each dose differently: the first-month price is rarely the price you stay on.

What the trials showed

In SURMOUNT-1 (72 weeks, adults with obesity without diabetes), tirzepatide 15mg produced an average body-weight reduction of about 20.9%, against 3.1% with placebo. In STEP 1 (68 weeks, similar population), semaglutide 2.4mg produced an average reduction of 14.9%, against 2.4% with placebo. The only direct head-to-head, SURMOUNT-5 (72 weeks, 750 adults, published in the New England Journal of Medicine in 2025), found average weight loss of 20.2% with tirzepatide versus 13.7% with semaglutide at maximum tolerated doses.

Read those numbers with care. They are trial averages in selected populations with structured support; individual results vary from far less to far more, weight regain is common after stopping, and a percentage difference in a trial is not a prediction for any one person. They are also not the only outcomes that matter: tolerability, existing conditions and drug interactions can all point a prescriber toward either medicine.

Safety information

The most common side effects of both are gastrointestinal: nausea, diarrhoea, constipation and vomiting, most often during dose escalation. Both carry warnings that prescribers assess individually, including around pancreatitis, gallbladder disease and use in pregnancy (both must not be used during pregnancy, and MHRA guidance highlights effective contraception while on treatment). This page deliberately does not reproduce full safety information: read the patient information leaflet for the prescribed medicine and the MHRA's GLP-1 guidance linked below, and report suspected side effects via the MHRA Yellow Card scheme.

What they cost in the UK today

Live lowest prices at each treatment's usual starting dose from the 12 regulated UK online providers we compare, re-checked automatically every 12 hours (last check 18 Aug 2026):

Treatment	Lowest first month	Lowest ongoing / 4 weeks	Providers priced
Mounjaro	£94	£119	12
Wegovy injection	£53	£73	11

Per-dose prices, provider evidence and multi-month estimates: Mounjaro comparison · Wegovy comparison · UK GLP-1 price index.

Questions worth asking a prescriber

Given my history, is either medicine unsuitable for me, and why?
What results and side effects should I realistically expect in the first three months?
What is the plan for dose escalation, and what will each stage cost me?
What happens when I stop: what support exists for maintaining weight?
How will my treatment be monitored, and by whom?

Where price information ends and clinical choice begins: we compare published prices and evidence so you can see the market clearly. The choice of medicine, if any, belongs in a consultation with a qualified prescriber who knows your history. Any regulated provider, including every provider listed on this site, will make that assessment before anything is prescribed.

Mounjaro vs Wegovy questions

Which is better, Mounjaro or Wegovy?

There is no single answer: "better" depends on your health history, tolerability, availability and budget, which is exactly why both are prescription-only. In the one head-to-head trial (SURMOUNT-5, 72 weeks), average weight loss was greater with tirzepatide than semaglutide (20.2% vs 13.7%), but individual responses vary widely and a prescriber weighs far more than a trial average.

Are Mounjaro and Wegovy available on the NHS?

Partly. Tirzepatide (Mounjaro) is being rolled out in primary care in phases under NICE guidance, prioritising people with the highest clinical need, and Wegovy is available through specialist weight-management services in some areas. Most people currently accessing either medicine for weight loss do so privately. Criteria and availability change; check with your GP or the NHS website for the current position.

How much do Mounjaro and Wegovy cost privately in the UK?

Live prices from the providers we compare start from the figures in the table above and change frequently. First-month offers usually carry conditions, and doses step up over the first months, so compare the ongoing price too: understanding true cost.