Wegovy vs GLP-1 medicines: clearing up the biggest confusion

The myth: 'Wegovy' and 'GLP-1' mean the same thing

This is the misconception worth clearing up first. GLP-1 stands for glucagon-like peptide-1, and it describes a whole class of medicines that act on the same receptor in your gut and brain. Wegovy is one member of that class, specifically semaglutide at 2.4mg (and now up to 7.2mg), made by Novo Nordisk. If you want to understand exactly how Wegovy and Ozempic relate to each other, our Wegovy vs Ozempic page explains the distinction in full, including why Ozempic should never be obtained for weight loss. Rybelsus is oral semaglutide licensed for diabetes. Neither Ozempic nor Rybelsus is a substitute for Wegovy.

Mounjaro (tirzepatide), made by Eli Lilly, goes a step further than a pure GLP-1: it activates both the GLP-1 receptor and the GIP receptor, making it the only dual-agonist weight-loss medicine with a UK licence. That mechanistic difference matters, because it partly explains the different trial results you'll see in the table below. Both Wegovy and Mounjaro are the medicines nume's prescribers work with. If you'd like an overview of how Wegovy works in practice, that page covers the mechanism in more detail, and the GLP-1 vs semaglutide page maps the full class for anyone who wants the wider picture.

What the evidence shows: weight loss and head-to-head data

For years the two medicines were compared only indirectly, because their trials used different populations and designs. SURMOUNT-1 (tirzepatide, 72 weeks, published in the New England Journal of Medicine) showed average body-weight reductions of around 20–21% at 15mg. STEP 1 (semaglutide 2.4mg, 68 weeks) showed around 15% on average. Both compared to placebo, both alongside lifestyle support.

A direct comparison arrived with SURMOUNT-5, a head-to-head trial published in the New England Journal of Medicine in 2025. Among 751 adults with obesity and no diabetes, tirzepatide produced greater average weight reduction than semaglutide 2.4mg over 72 weeks. NICE's appraisal of tirzepatide (TA1026) also noted that indirect comparisons favour tirzepatide, though it acknowledged the evidence base is still maturing. The gap is narrowing slightly at the newer 7.2mg semaglutide dose, approved by the MHRA in January 2026, which trial data suggest delivers around 20.7% average weight loss, closer to tirzepatide's headline results. Worth knowing, though it doesn't settle the question of which medicine suits any particular person.

The table below summarises the key factual differences. Figures are from published trials and UK regulatory approvals; hedge language reflects genuine uncertainty in cross-trial comparisons.

Side-effect profile and practical day-to-day differences

Both medicines share a similar side-effect pattern, because both slow gastric emptying and act on appetite centres in the brain. Nausea, loose stools, constipation, indigestion and fatigue are the most commonly reported, usually most noticeable in the first few weeks or after a dose increase, and often settling without intervention. The comparison with Saxenda covers how liraglutide's daily-injection burden differs if that's relevant context for your decision.

Where practical differences do emerge: Wegovy now exists as a once-daily tablet (oral semaglutide, approved by the MHRA on 11 June 2026), which some people strongly prefer over injections. The Wegovy tablet is taken first thing in the morning on an empty stomach, before coffee or breakfast, and needs no refrigeration, a meaningful convenience advantage over both the Wegovy pen and Mounjaro's KwikPen, which both need to be kept cold. If you're weighing up the injection vs the tablet, our prescribers can talk through which format fits your routine. Mounjaro has no oral equivalent in the UK at this time.

The MHRA's guidance on GLP-1 medicines (available on GOV.UK) covers the known safety considerations for both, including the January 2026 Drug Safety Update flagging acute pancreatitis as an infrequent but serious risk: seek urgent help for severe stomach pain that radiates to the back. The NHS page on semaglutide sets out the full side-effect and safety picture for Wegovy users specifically.

Which one is right for you, and how to find out

Neither medicine is universally better. Tirzepatide's average results are currently stronger in trials. Semaglutide in oral form offers a needle-free option that didn't exist a year ago. Individual responses vary considerably: someone who loses 18% on semaglutide might lose less on tirzepatide, or vice versa. For a closer look at how the branded product and its active ingredient compare, our semaglutide vs Wegovy page is a useful read before your consultation, particularly if you've seen compounded or generic versions advertised elsewhere. Your medical history, any other medicines you take (oral contraceptives, for example, need extra consideration with tirzepatide, a detail our clinical team covers at consultation), and your own preferences all feed into the decision.

What the NICE appraisal of tirzepatide and the TA875 recommendation for semaglutide make clear is that both medicines belong inside a clinically supervised programme, not bought from an unverified seller. Fake pens are a documented problem (the MHRA has seized large quantities of counterfeit weight-loss medicine from illegal UK supply chains) and the only safe route is a prescription issued by a registered prescriber following a proper assessment. You can check any online pharmacy on the GPhC register before you hand over any details.

At nume, a real prescriber reviews every consultation the same day. There's no algorithm making the call. If you'd like to explore your options, the weight-loss treatments page is the starting point, or you can read more about how Wegovy compares across a broader range of alternatives. Which suits you is a clinical decision our prescribers make with you, not a judgement we'd make from a webpage.