Your guide to Wegovy: what the evidence says and how it works

The trial data that shaped Wegovy's UK licence

The STEP 1 study, published in the New England Journal of Medicine, followed 1,961 adults with obesity over 68 weeks. Participants taking semaglutide 2.4 mg weekly alongside lifestyle support lost an average of around 15% of their body weight, roughly ten times the result seen with placebo. That figure is drawn from a broad population: people with and without type 2 diabetes, across a range of starting weights and ages. It is worth treating it as a population average rather than a personal forecast, because individual results vary considerably depending on adherence, diet, activity and biology.

More recently, the MHRA approved a 7.2 mg maintenance dose. The dedicated single-dose pen was confirmed on 14 April 2026 for adults with a BMI of 30 or above. Trials at this higher dose reported average weight losses of around 20.7% over 72 weeks, narrowing the gap with tirzepatide at its highest dose. Whether the 7.2 mg pen is the right option for a given patient is a clinical question, not a formulaic one. How titration works in practice is a separate topic worth reading alongside this one.

A question our prescribers hear most weeks: "If I've seen bigger numbers quoted online, which figure is real?" The answer is that different trials use different doses, durations and populations. The 15% figure from STEP 1 is the benchmark for the licensed 2.4 mg dose; the higher numbers refer to newer dosing or selected adherent subgroups.

How semaglutide produces these effects

Semaglutide is a GLP-1 receptor agonist, it mimics glucagon-like peptide-1, a gut hormone released naturally after eating. By binding to GLP-1 receptors in the brain and digestive system, it reduces appetite, increases feelings of fullness after smaller portions, and slows the rate at which food leaves the stomach. None of this bypasses conscious eating; it changes the biological signals that govern how hungry you feel and how quickly those signals settle.

It is worth being precise about what Wegovy is and is not. It is not Ozempic. Both contain semaglutide, but Ozempic is licensed for type 2 diabetes and carries different dosing. The semaglutide overview explains the distinction in full. Wegovy is also now available as a once-daily tablet, oral semaglutide approved by the MHRA in June 2026 as the first oral GLP-1 licensed for weight management in the UK. The injection and tablet are different formulations with different dosing schedules; a prescriber will discuss which presentation suits your circumstances.

Because semaglutide works on appetite signalling rather than forcing calorie restriction, the medicine works best when paired with changes to eating patterns and activity. The NHS England guidance on weight management injections is explicit on this: the medicine is an adjunct to lifestyle change, not a replacement for it.

Who the UK licence covers (and what NICE says

The licensed eligibility criteria for Wegovy are adults with a BMI of 30 or above, or a BMI of 27 to 29.9 alongside at least one weight-related condition) for example, high blood pressure, prediabetes, dyslipidaemia or obstructive sleep apnoea. Lower thresholds of 2.5 kg/m² apply for South Asian, Chinese, Middle Eastern, Black African or African-Caribbean backgrounds under UK clinical guidance. Meeting these numbers is a starting point, not a guarantee: a prescriber considers the full clinical picture, including any contraindications and your history.

NICE recommends Wegovy (TA875) only when used for a maximum of two years, within a specialist weight management service that provides multidisciplinary support, for adults with a BMI of 35 or above alongside at least one weight-related comorbidity, or those meeting lower-BMI specialist-referral criteria. That recommendation shapes NHS access specifically. Private prescriptions are not bound by the NICE implementation pathway, though they must still follow the medicine's licensed indications.

Wegovy is not recommended during pregnancy, breastfeeding or when trying to conceive, and it is not licensed for people under 18. Anyone with a history of medullary thyroid carcinoma, multiple endocrine neoplasia type 2, or a personal history of pancreatitis should discuss this with a prescriber before any consideration of treatment. If you want to explore whether you are likely to be eligible, the treatment overview sets out the process clearly.

Side effects and what to watch for

The most commonly reported side effects are gastrointestinal: nausea, constipation, diarrhoea, indigestion and burping. These are typically most pronounced in the first few weeks or after a dose increase, and they tend to settle as the body adjusts. Starting at the lowest dose and titrating slowly is specifically designed to manage this, the titration schedule is not about building to a target quickly, it is about tolerability first.

A small number of people experience more serious effects. Severe, persistent stomach pain that spreads to the back, with or without vomiting, needs urgent medical attention, this can indicate acute pancreatitis. The MHRA Yellow Card scheme allows patients and healthcare professionals to report suspected side effects, and doing so helps build the post-market safety picture for newer medicines. Wegovy's Black Triangle status means it is subject to additional monitoring for exactly this reason.

For people taking oral contraceptives, there is no equivalent evidence of reduced pill absorption with semaglutide that there is with tirzepatide, though any concerns about contraception should be discussed with a prescriber. The full semaglutide guide covers the safety profile in more depth, and if you are new to the medicine, our Wegovy user guide walks you through everything from your first injection to ongoing use. If you have a scheduled surgical procedure, tell the anaesthetist and surgical team that you are using this medicine: guidance on Wegovy and anaesthesia explains the practical considerations.

Missed doses are common during longer-term treatment. The decision on what to do depends on how much time has passed, and the answer is always deferred to the Patient Information Leaflet and your prescriber, what to do if you forget a dose covers this specifically. Ready to discuss whether Wegovy suits your situation? Speak to our prescribers through a free consultation, reviewed the same day by a GPhC-registered Independent Prescriber.