Wegovy and Mounjaro: What's the Difference Between Them?

You're weighing up two medicines and not sure which one fits your situation

That's exactly the position most people are in when they come to us. They've read that Mounjaro produces bigger average weight losses. They've also read that Wegovy has been around longer, has more post-approval data, and has a dedicated oral tablet version that arrived in the UK in 2026. Neither headline tells the full story, and a decision made on a headline alone can land you on the wrong treatment.

Mounjaro (tirzepatide, made by Eli Lilly) is a dual GIP and GLP-1 receptor agonist, the only licensed weight-loss medicine in the UK to activate both of those gut-hormone pathways. That dual action influences appetite, fullness and the rate at which the stomach empties. Wegovy (semaglutide, made by Novo Nordisk) targets the GLP-1 pathway only. Both are subcutaneous injections taken once a week; both start at a low dose and are titrated upward by the prescriber over several months. If you want to understand what's the difference between Mounjaro and Wegovy in terms of their side-effect profiles and practical use day to day, our Wegovy vs Mounjaro guide covers the clinical detail in depth.

The decision of which to prescribe is a clinical one. Our prescribers weigh your BMI, your health history, any medicines you already take, and your own preferences before recommending either.

What the trial evidence actually shows

The SURMOUNT-1 trial (2,539 adults with obesity, 72 weeks) found that tirzepatide at the highest dose produced an average body-weight reduction of around 20–21%, with some analyses putting it closer to 22.5% at 15mg. The STEP 1 trial for semaglutide at 2.4mg (the standard Wegovy maintenance dose) reported an average reduction of around 15% over 68 weeks. Both are published in the New England Journal of Medicine and are the basis for NICE's appraisals of both medicines.

In 2025, a direct head-to-head trial called SURMOUNT-5 compared tirzepatide against semaglutide 2.4mg in 751 adults with obesity and no diabetes over 72 weeks. Tirzepatide produced a greater average weight reduction. It is worth knowing, however, that semaglutide's 7.2mg dose (approved by the MHRA in January 2026 and available as a dedicated single-dose pen since April 2026) reported around 20.7% average weight loss in its trials, which narrows the gap considerably. Neither medicine guarantees a specific result for any individual; clinical trial averages describe populations, not you.

The plain-English comparison below summarises the key clinical differences, drawn from NICE's appraisal of tirzepatide (TA1026) and NICE's appraisal of semaglutide (TA875).

A note on Ozempic) because it keeps coming up

Many people comparing Wegovy and Mounjaro have also heard of Ozempic and wonder where it fits. The short answer: Ozempic is semaglutide, the same active ingredient as Wegovy, but it is licensed by the MHRA for type 2 diabetes management, not for weight loss. Prescribing it for weight loss would be off-label. If you are researching the difference between Ozempic and Mounjaro, the clinical distinction matters: Mounjaro is the weight-management option with the head-to-head evidence; Ozempic is not licensed for that purpose in the UK, and it is not something a regulated weight-loss service would prescribe for this indication.

Similarly, tirzepatide is sold in the United States under the brand name Zepbound. Zepbound does not exist as a UK product; the UK brand is Mounjaro. If you are reading content that discusses Zepbound availability or pricing in a UK context, that content is describing a product that is not authorised here. Our explainer on Wegovy vs Zepbound covers this distinction clearly, and our Mounjaro vs Ozempic page goes into more detail on the diabetes-vs-weight-loss licensing split.

What actually arrives, and how the choice gets made

Whichever medicine is clinically appropriate, the practical experience is similar: a pre-filled pen, once weekly, dispatched from our GPhC-registered pharmacy and delivered to your door by DPD in a plain box, no branding, no indication of what's inside. You track it on your phone. The pen itself is straightforward to use; our prescribers and aftercare team are available seven days a week if anything feels uncertain.

The cost context differs between the two. Eli Lilly raised Mounjaro's UK list price substantially from September 2025, so private monthly costs for the higher doses are typically higher than they were. For a detailed breakdown of how prices compare across doses and providers, our Mounjaro vs Wegovy price comparison sets out what is publicly reported. A wider look at weight-loss treatment options at nume covers both medicines alongside the newer oral option.

Which suits your health, your history and your circumstances is not a decision to make from a comparison table. It is a clinical one, made with our prescribers, who review your full consultation before anything is recommended. Check your eligibility and start your free consultation to find out which option (if either) is right for you.