Mounjaro or Wegovy: which one produces more weight loss?

Step 1: understand what each medicine is and what the trials measured

Mounjaro (tirzepatide, made by Eli Lilly) activates two gut-hormone receptors (GIP and GLP-1) which together reduce appetite and slow gastric emptying. Wegovy (semaglutide, made by Novo Nordisk) targets the GLP-1 receptor only. That dual-pathway mechanism is one reason researchers expected tirzepatide to outperform semaglutide, and the trials broadly confirmed it.

The core evidence for each medicine came from separate phase-3 programmes. SURMOUNT-1 enrolled around 2,539 adults with obesity and no type 2 diabetes over 72 weeks; at the highest 15mg dose, average body-weight reduction was around 20–21%, as published in the New England Journal of Medicine. STEP 1, the equivalent Wegovy trial at 2.4mg over 68 weeks, found average reductions of around 15%, also published in the NEJM. Comparing those figures is tempting but imperfect, different trial populations, different durations, different starting weights. That is why SURMOUNT-5 matters.

For a fuller side-by-side overview of how the two medicines are licensed and structured, the Wegovy vs Mounjaro guide on this site covers the detail in one place.

Step 2: the head-to-head data from SURMOUNT-5

SURMOUNT-5 was a 72-week open-label trial that randomised 751 adults with obesity and no diabetes to either tirzepatide or semaglutide 2.4mg, giving both groups the same follow-up conditions. Tirzepatide produced meaningfully greater average weight loss. NICE referenced these findings in its appraisal of tirzepatide (TA1026) noting that indirect comparisons also favoured tirzepatide, and the head-to-head data reinforced that picture.

One important nuance: Wegovy now has a licensed 7.2mg maintenance dose, approved by the MHRA in January 2026 and available as a dedicated single-dose pen from April 2026. Early data at this higher dose reported average weight loss of around 20.7% over 72 weeks, which narrows the gap with tirzepatide 15mg considerably. That 7.2mg option did not exist when most of the comparative trial work was done, so the picture is still developing.

The comparison table below captures the current state of the evidence.

Trial figures are group averages; individual results vary. Source: NICE TA1026; NEJM SURMOUNT-1; NEJM STEP 1; SURMOUNT-5 (NEJM, 2025).

Step 3: what those numbers cannot tell you

A trial average describes a group. Your starting weight, your metabolic history, which weight-related conditions you have, and how your body responds to each medicine's receptor pathway all shape your individual result. Some people find semaglutide suits them better in terms of side-effect profile; others tolerate tirzepatide more easily. The GI side effects (nausea, loose stools, constipation) are broadly similar for both, tend to be most noticeable around dose increases, and usually settle. There is no reliable way to predict, from the outside, which medicine will produce the better outcome for a specific person.

Cost is also a factor worth thinking about honestly. If you are weighing up Mounjaro and Wegovy on price, the treatment page is the right place to see current figures rather than comparing body-copy numbers that date quickly. What the trial results do confirm is that both medicines are substantially more effective than lifestyle intervention alone, which is why a prescriber asking the right clinical questions, rather than a league table, is the better guide to which one to use.

If you want to read more about whether Wegovy or Mounjaro is more effective for weight loss, that page looks at how effectiveness stacks up across different doses and populations, and if you are still weighing things up, our Mounjaro versus Wegovy weight loss guide goes deeper on the evidence across the licensed indications. For a broader comparison of how the two medicines perform in practice, the Wegovy vs Mounjaro for weight loss page brings together the key evidence in one place, and if you are trying to decide which option suits your situation, the what's better, Mounjaro or Wegovy for weight loss page walks through the clinical factors that tend to tip the decision one way or the other.

How the clinical decision gets made (and where nume fits in

A quick note on timing: if you are reading this on a Monday morning, or just before a bank holiday, it is worth knowing that orders placed before 12pm on any working day are dispatched the same day once approved) so the practical delay is smaller than you might expect.

At nume, every consultation is reviewed by a GPhC-registered Independent Prescriber from our clinical team. They assess your weight, your health history, any medications you are taking, and your clinical picture as a whole. The question of whether you might lose more weight on Mounjaro or Wegovy is exactly the kind of question that gets answered through that review, not by a chart. Both medicines are licensed for weight management by the MHRA, and both are stocked and dispensed through our GPhC-registered pharmacy (registration number 9012878, verifiable at the GPhC register).

Which suits you is a clinical decision our prescribers make with you. The right starting point is a free consultation, where the evidence above gets applied to your actual situation.