Wegovy or Mounjaro: which is more effective for weight loss?

Step 1: understand what each medicine is and how they differ mechanically

Mounjaro (tirzepatide, made by Eli Lilly) activates two gut-hormone receptors (GIP and GLP-1) at the same time. It is the only dual-agonist weight-loss medicine licensed in the UK. Wegovy (semaglutide, made by Novo Nordisk) targets GLP-1 alone. Both slow gastric emptying and reduce appetite; if you want to understand what is more effective, Mounjaro or Wegovy, the dual mechanism of tirzepatide appears to produce a stronger suppression effect at higher doses, which is reflected in the trial data.

Neither medicine is Ozempic. Ozempic is also semaglutide but is licensed in the UK for type 2 diabetes, not weight management. If you are looking at a comparison purely for weight loss, the relevant products are Mounjaro and Wegovy. Our page on Mounjaro vs Ozempic covers that distinction in full.

Both require a prescription following a clinical assessment. That point matters practically: a prescriber does not pick the medicine with the bigger percentage and hand it over. They weigh your medical history, any existing conditions, current medicines and your tolerance of side effects before recommending one over the other.

Step 2: read the trial numbers, cited, hedged and put in context

The SURMOUNT-1 trial, published in the New England Journal of Medicine, found average body-weight reductions of around 20–21% at the 15mg tirzepatide dose over 72 weeks. The STEP 1 trial for semaglutide 2.4mg (Wegovy) reported an average of roughly 15% over 68 weeks, also published in the NEJM. Those are different trials with different populations, so a direct read-across has limits.

The more telling data comes from SURMOUNT-5, a 72-week open-label head-to-head trial published in 2025, which directly compared tirzepatide against semaglutide 2.4mg in 751 adults with obesity and no diabetes. Tirzepatide produced a meaningfully greater average reduction. How those figures translate into real-world results is covered in detail on a dedicated page. NICE's appraisal of tirzepatide (TA1026) notes that indirect comparisons favour tirzepatide.

One important caveat: Wegovy's 7.2mg dose was approved by the MHRA on 14 April 2026. Early data puts average weight loss at around 20.7% at that dose over 72 weeks, which approaches tirzepatide's highest-dose results. The gap between the two medicines is narrowing as Wegovy's ceiling rises. A fuller breakdown of Wegovy versus Mounjaro for weight loss sets this evolving evidence alongside the licensed eligibility criteria for each.

Step 3: compare them on the factors that affect everyday life

Numbers aside, people often make their choice on practical grounds: injection frequency, dose schedule, storage at home, side-effect profile and cost. The table below captures the key points factually.

On side effects, both share a GI-led profile: nausea, constipation, diarrhoea and indigestion are the most commonly reported, particularly after starting or a dose increase. They tend to ease over the first couple of weeks. Some people find one medicine settles better for their stomach than the other, that is a reason clinical review before every repeat matters. The NHS tirzepatide medicines page and the equivalent semaglutide page both carry detailed, patient-level side-effect information worth reading before you decide.

Storage is identical in principle for both: keep the pen in the fridge, ideally not wedged against the freezer shelf at the back of the fridge door, and check the patient leaflet for the exact permitted time at room temperature before use. Neither pen should be frozen.

On cost, both are private prescriptions if accessed through a service like our weight-loss treatment options. The price difference between Mounjaro and Wegovy varies by dose and provider; a fuller breakdown is on that page. Neither is cheap at higher maintenance doses.

Step 4: what the right choice actually depends on

Choosing between these two medicines is a clinical decision, not a consumer one. A prescriber will consider whether you have type 2 diabetes alongside obesity (both hold that licence), which conditions you have, what other medicines you take, your starting BMI, and how you have responded to treatment before if you are transferring from elsewhere.

The oral alternative is also worth knowing about: Wegovy is now available as a daily tablet (approved by the MHRA on 11 June 2026), which suits people who prefer not to inject. Whether Mounjaro or Wegovy is the better fit for you covers that three-way picture in more depth.

At nume, our clinical team (led by our prescribers, including our clinical lead) reviews your consultation personally, not algorithmically. Which suits you is a clinical decision our prescribers make with you, based on your full picture. Speak to our prescribers through a free consultation to get the answer that applies to your situation specifically.