What does Mounjaro do that Wegovy doesn't — and does it matter?

Why does Mounjaro target two receptors when Wegovy only targets one?

Wegovy (semaglutide) is a GLP-1 receptor agonist. GLP-1 is a hormone released after eating; it slows how quickly the stomach empties, signals fullness to the brain and nudges the pancreas to manage blood sugar. Mounjaro (tirzepatide) does all of that and adds a second action: it also activates the GIP receptor. GIP is another post-meal gut hormone, and combining the two pathways appears to produce a stronger appetite-suppressing signal than either alone. The NHS medicines page on tirzepatide describes it as the only dual GIP and GLP-1 receptor agonist currently licensed in the UK for weight management.

What this means practically is that tirzepatide seems to reduce hunger (and food enjoyment, for some people) more consistently than semaglutide does. That said, individual responses vary considerably, and if you are curious about whether Wegovy works like Mounjaro in practice, the mechanisms behind each medicine help explain where the similarities end. The dual mechanism is a pharmacological advantage, not a certainty.

For a side-by-side look at how the two medicines compare across a wider range of factors, the Wegovy vs Mounjaro comparison covers eligibility, dosing schedules and trial data in more depth.

What do the trial results actually show?

The clearest evidence comes from SURMOUNT-5, a direct head-to-head trial published in the New England Journal of Medicine in 2025, comparing tirzepatide with semaglutide 2.4mg over 72 weeks in adults with obesity and no diabetes. Tirzepatide produced greater average weight loss. SURMOUNT-1, involving 2,539 adults, found average body-weight reductions of around 20–21% at the 15mg dose of tirzepatide over 72 weeks. The STEP 1 trial for semaglutide at 2.4mg reported around 15% average weight loss over 68 weeks. Wegovy's newer 7.2mg dose narrows this gap, with trials reporting roughly 20.7% average loss, though the head-to-head data for that higher dose is not yet as extensive.

The table below summarises the key differences as they stand today.

The full effectiveness comparison between semaglutide and tirzepatide explores the SURMOUNT-5 data and what indirect comparisons from NICE suggest about the relative results.

Are there things Wegovy does that Mounjaro doesn't?

Yes. Semaglutide holds additional UK authorisations that tirzepatide does not. Wegovy has been approved to reduce the risk of major cardiovascular events in eligible adults, and in July 2026 the MHRA granted conditional approval for semaglutide in MASH, a form of fatty liver disease, as announced on GOV.UK. Neither of these authorisations currently applies to Mounjaro. For people with obesity and established cardiovascular disease, that cardiovascular indication is clinically relevant and may influence which medicine a prescriber recommends.

Wegovy is also now available in tablet form. The MHRA approved the Wegovy oral tablet in June 2026, making it the first oral GLP-1 medicine licensed in the UK for weight management, useful for anyone who would prefer to avoid injections entirely. Mounjaro is only available as a once-weekly injection.

If you're weighing whether to switch between these medicines, what happens when moving from Mounjaro to Wegovy is covered separately, including what to expect in the transition period. It is also worth reading about whether Wegovy is worth trying if Mounjaro has not worked for you, as the answer depends on more than simply switching from one medicine to the other.

Which one is right for you?

That depends on factors a prescriber needs to consider: your BMI, any existing conditions, other medicines you take, how your body responded to any previous treatment, and your preference around injections versus tablets. NICE recommends tirzepatide under TA1026 for adults with BMI ≥35 and at least one weight-related comorbidity; semaglutide is recommended under TA875 within specialist weight management services for a maximum of two years. Lower BMI thresholds apply under both appraisals for people from certain ethnic backgrounds, in line with NICE TA1026 guidance.

In private practice, both medicines are available to adults with BMI ≥30, or ≥27 with a relevant weight-related condition, subject to clinical assessment. The dual mechanism of Mounjaro makes it a strong option for many, but greater average trial results do not mean it is automatically the better choice for every individual. Which suits you is a clinical decision our prescribers make with you, based on your full picture. You can explore both options or ask any of these questions directly when you start your free consultation.