Wegovy or Mounjaro: which is actually better for weight loss?

They work differently, and that difference matters

Both medicines reduce appetite and slow the rate at which food leaves your stomach, but they do it through different receptors. Wegovy (semaglutide) activates one gut-hormone pathway: GLP-1. Mounjaro (tirzepatide) activates two: GLP-1 and GIP. That dual action is thought to be part of why tirzepatide tends to produce larger weight reductions in trials, though the full picture is still being studied. Semaglutide has been in clinical use longer, so there is a larger body of real-world evidence behind it. Tirzepatide is the only dual-agonist weight-loss medicine currently licensed in the UK. For a side-by-side look at how the injectable forms compare in practice, the Wegovy vs Mounjaro overview covers the mechanisms in more detail. One point worth knowing: Ozempic is also semaglutide, but it carries a diabetes licence, not a weight-loss one, that distinction is explored on our Ozempic vs Mounjaro page.

Both medicines are Black Triangle (▼) products, meaning the MHRA requires additional monitoring. That is standard for newer medicines and not a cause for concern, it reflects the regulators doing their job.

What the trial data actually shows

In SURMOUNT-1 (72 weeks, involving around 2,500 adults with obesity and no diabetes), tirzepatide at 15mg produced an average body-weight reduction of around 20–21%, with some analyses reaching approximately 22.5%. The STEP 1 trial for semaglutide 2.4mg (68 weeks, similar population) showed an average reduction of roughly 15%. Those figures come from the SURMOUNT-1 paper in the New England Journal of Medicine and the corresponding STEP 1 publication respectively, cite them, don't just quote them.

More directly: in SURMOUNT-5, a head-to-head trial published in the NEJM in 2025, tirzepatide produced greater average weight loss than semaglutide 2.4mg over 72 weeks in adults with obesity but without diabetes. NICE's appraisal of tirzepatide (TA1026) noted that indirect comparisons also favour tirzepatide. The gap narrows with Wegovy's newer 7.2mg dose, which trial data suggests produces around 20.7% average weight loss, approaching tirzepatide's results. Specific dose availability for either medicine is confirmed at consultation, not assumed. If you're weighing up what's better, Mounjaro or Wegovy, specifically for weight loss, our dedicated page works through the trial numbers in more detail. You can also read more about the cost dimension of this choice on our tirzepatide vs semaglutide cost page.

Practical differences that influence the decision

Beyond the numbers, several day-to-day factors matter. Both medicines are once-weekly injections that need refrigerating, think of the pen sitting in the fridge door rather than tucked at the back where it might freeze. Storage is straightforward for most people; the exact room-temperature window if you need to travel is always in the Patient Information Leaflet, not something to guess at.

Wegovy now also comes as a daily tablet (the 25mg oral form), approved by the MHRA in June 2026 as the UK's first licensed oral GLP-1 medicine for weight management. For people who find injections difficult or want a needle-free option, that changes the conversation. The side-effect profile for both medicines is dominated by gastrointestinal effects (nausea, loose stools, constipation, indigestion) most noticeable after starting or after a dose step, and typically settling within days to a couple of weeks. The order and character of those symptoms can differ slightly between the two, and individual tolerance varies considerably. Eligibility thresholds are the same for both medicines in private practice: BMI of 30 or above, or 27 and above with at least one weight-related condition such as high blood pressure, high cholesterol, or type 2 diabetes. Lower thresholds apply for some ethnic backgrounds under UK guidance. For a broader look at how these medicines sit alongside other options, our Saxenda, Wegovy and Mounjaro comparison is worth reading.

NHS vs private access, and what the NICE guidance says

NICE recommends tirzepatide under TA1026 for adults with a BMI of 35 or above and at least one weight-related comorbidity, with NHS prescribing through GP practices beginning from April 2026 under a phased rollout. Wegovy is recommended under TA875, but only through specialist weight management services and for a maximum of two years, waiting lists tend to be long. If you don't meet the current NHS criteria or prefer not to wait, private treatment through a regulated pharmacy is the alternative. NICE's full tirzepatide guidance (TA1026) and the semaglutide recommendation (TA875) are both publicly available if you want to read the committee's reasoning. Confirming which pharmacy you're using is registered is straightforward: the GPhC register lists nume's pharmacy, premises number 9012878.

The bottom line is this: tirzepatide shows larger average weight loss in trials, including head-to-head against semaglutide 2.4mg. But average trial results don't predict individual responses, and contraindications, existing conditions and personal preference all shift the decision. If you're still working out what's best, Mounjaro or Wegovy, for your situation, our overview brings the key considerations together in one place. Which suits you is a clinical judgement our prescribers make with you. If you're ready to work through it, start your free consultation and a GPhC-registered prescriber will review your answers the same day.