Mounjaro®
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Start journey Learn moreWhat the evidence actually shows when Wegovy and Mounjaro go head-to-head
What the SURMOUNT-5 trial found when the two medicines competed directly
For years, clinicians compared Wegovy and Mounjaro using separate trial populations — a reasonable approach, but not the same as a controlled head-to-head. SURMOUNT-5 changed that. The open-label trial ran for 72 weeks in 751 adults living with obesity and no diabetes, and it put tirzepatide (Mounjaro) directly against semaglutide 2.4mg (Wegovy). Tirzepatide produced greater average weight reduction. That finding is cited in NICE's appraisal of tirzepatide (TA1026), which notes that indirect comparisons also favour tirzepatide over semaglutide for weight loss.
The gap has narrowed with the arrival of the higher-dose Wegovy 7.2mg pen, approved by the MHRA in April 2026, which produced around 20.7% average weight loss in trials. Tirzepatide at its 15mg maintenance dose averaged around 20–21% in SURMOUNT-1. At their respective maximums, the two medicines are closer than they used to be. For a more granular look at which produces greater weight loss by dose, we've covered those figures separately. The short version: the margin exists, but it is not as wide as the early narrative suggested, and it does not tell you which will work better for you personally.
The comparison table below sets out the key trial figures side by side.
| Factor | Mounjaro (tirzepatide) | Wegovy (semaglutide) |
|---|---|---|
| Mechanism | Dual GIP + GLP-1 receptor agonist | GLP-1 receptor agonist |
| Average weight loss (pivotal trial) | ~20–21% at 15mg over 72 weeks (SURMOUNT-1) | ~15% at 2.4mg over 68 weeks (STEP 1); ~20.7% at 7.2mg |
| Head-to-head result (SURMOUNT-5) | Greater average loss vs semaglutide 2.4mg | Lower average loss vs tirzepatide at same duration |
| UK licence (weight) | BMI ≥30, or ≥27 with a weight-related condition | BMI ≥30, or ≥27 with a weight-related condition |
| Injection frequency | Once weekly | Once weekly |
| NICE recommendation | TA1026 (Dec 2024) | TA875 (Mar 2023); max 2 years, specialist services |
Why the numbers alone cannot answer whether Wegovy or Mounjaro works better for you
Trial averages are population statistics. A person who loses 22% of their body weight on tirzepatide and one who loses 8% are both inside that distribution. The same is true for semaglutide. Your response depends on your biology, your current metabolic picture, your tolerability to GI side effects during titration, any medicines you already take, and how your weight-related conditions interact with each drug's mechanism.
Mounjaro activates two gut-hormone receptors, GIP and GLP-1. Wegovy activates one. That dual action is the reason most researchers attribute tirzepatide's stronger average results. But individual variation means the margin is not guaranteed to hold for every patient. Some people do respond more strongly to semaglutide, and there are cases where Wegovy worked better than Mounjaro, which is why the question of whether Wegovy works better than Mounjaro for certain individuals is a live clinical conversation, not a settled debate.
Side-effect tolerability also shapes the practical outcome. Both medicines have a GI-led profile: nausea, loose stools, constipation, and reflux are common especially around dose increases, and usually settle within days to a couple of weeks. If one medicine is poorly tolerated at a therapeutic dose, the other may suit better regardless of the average trial figures. A prescriber who knows your history makes that call. You can read about switching between the two medicines if that question is already on your mind.
Cost, NHS access and the practical differences that matter alongside the clinical ones
Neither medicine is available over the counter. Both are prescription-only, and a clinician assessing your health history, current medicines, and weight-related conditions is the legal and clinical prerequisite. That is not a formality — it is the mechanism that makes these medicines safe to use.
On the NHS, tirzepatide is being rolled out in phases under NICE TA1026, with strict BMI and comorbidity thresholds that tighten further the earlier in the rollout. Wegovy on the NHS requires referral to a specialist weight management service under TA875, with waiting lists that vary widely by area. For most people asking this question today, private prescription is the realistic route. The cost difference between the two medicines through a private pharmacy is worth factoring in; how the prices compare is something we've laid out plainly elsewhere.
One practical note: if you're planning to start treatment, ordering before the Monday 12pm cut-off means same-day dispatch and delivery the next working day, useful if you're timing a start around a work trip or holiday rather than mid-week when plans shift.
If you want to go deeper on the mechanism rather than just the results, the tirzepatide versus semaglutide comparison covers the pharmacology in more detail. For a broader overview of your treatment options, the weight-loss treatment page is a useful starting point. Our clinical team reviews every consultation personally, the decision about which medicine suits you is made with a prescriber, not by an algorithm.
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