What medicine is Wegovy, and how does it work?

What the STEP 1 trial established about semaglutide

The foundational evidence for Wegovy as a weight-management medicine came from the STEP programme, a series of large randomised trials run across multiple countries. STEP 1, published in the New England Journal of Medicine, enrolled adults with obesity or overweight plus at least one weight-related condition, without type 2 diabetes. Over 68 weeks, participants taking semaglutide 2.4 mg weekly alongside a reduced-calorie diet and increased activity lost an average of roughly 15% of their starting body weight. The placebo group lost around 2.4%. That gap is clinically significant: it represents a level of weight reduction that, at a population level, carries genuine implications for conditions such as high blood pressure, sleep apnoea and joint load. These are the data on which the MHRA based its UK approval, and on which NICE built its guidance. They are also the reason Wegovy is not a lifestyle supplement or an over-the-counter product, the clinical evidence places it firmly in the prescription-medicine category, where individual assessment is part of the treatment, not a bureaucratic hurdle.

It is worth noting that trial conditions (structured diet support, regular follow-up) tend to produce better results than unsupported real-world use. A prescriber who monitors your progress and adjusts your plan is part of what makes the treatment work.

Semaglutide's mechanism: one receptor, measurable effects

GLP-1 (glucagon-like peptide-1) is a hormone your gut releases after you eat. In people with obesity, this signalling system is often blunted. Semaglutide binds to GLP-1 receptors in the brain's appetite centres and in the gut wall, doing two things at once: it dials down hunger signals reaching the brain, and it slows how quickly food leaves the stomach. The practical result is that you feel full sooner and that fullness lasts longer. You can read a fuller account of how this mechanism translates into the weekly injection routine on the Wegovy overview page. The medicine does not burn fat directly; it changes the hormonal environment that governs appetite, so that eating less becomes genuinely easier rather than a matter of endurance. That distinction matters for setting realistic expectations: Wegovy works with your biology, but it still requires the reduced-calorie diet and increased activity the licence specifies.

Semaglutide is a GLP-1 receptor agonist specifically. This places it in the same drug class as some other weight-management medicines, but it activates only the GLP-1 pathway, a distinction that becomes relevant when comparing it with newer dual-receptor options. For the difference in practical terms, the weight-loss treatment overview covers both.

UK licensing: what Wegovy is (and is not) approved for

The MHRA has licensed Wegovy for weight management in adults with a BMI of 30 or above, or a BMI of 27 or above if they also have at least one weight-related condition such as high blood pressure, dyslipidaemia, type 2 diabetes or obstructive sleep apnoea. It must be used alongside a reduced-calorie diet and increased physical activity. It carries a Black Triangle (▼) status, which signals to healthcare professionals and patients that additional post-market safety monitoring is in place, not that the medicine is new to the world, but that the MHRA continues to collect real-world data actively.

A common question is whether Wegovy and Ozempic are the same medicine. Both contain semaglutide, but Ozempic is licensed for type 2 diabetes management, not weight loss. Using a diabetes medicine for weight management outside its licence is something a prescriber must evaluate individually, and it is not the same clinical situation as being prescribed Wegovy, a medicine specifically approved for weight loss. Similarly, semaglutide's approved weight-loss dose (2.4 mg weekly maintenance) is higher than the doses used in diabetes management. One quick check you can do right now: the MHRA's Yellow Card scheme at yellowcard.mhra.gov.uk lists medicines by name with their approved indications, it takes under a minute to confirm what any medicine is authorised for in the UK.

Private access, NHS routes, and what a clinical assessment involves

NICE recommended semaglutide (Wegovy) for NHS use in 2023, but under specific conditions: for a maximum of two years, within a specialist weight management service, for adults with a BMI of 35 or above and at least one weight-related comorbidity (thresholds are lower for some ethnic backgrounds under UK guidance). If fewer than 5% of body weight is lost after six months at the maintenance dose, continuing is reviewed. In practice, NHS access involves referral to a specialist service and, in many areas, a significant wait. The NICE appraisal TA875 sets out the full criteria.

For people who do not meet NHS thresholds or who prefer not to wait, a regulated private pharmacy provides a lawful alternative route, provided the medicine is dispensed against a valid prescription from a registered prescriber who has assessed your eligibility. You can explore what that assessment covers and what life on Wegovy actually feels like day to day on the what Wegovy is like page. If cost is a consideration, the Wegovy cost context page explains what private treatment typically includes and why the price varies between providers. The medicines themselves are prescription-only; the clinical assessment is not optional, and a prescriber's judgment cannot be replaced by a low price.

At nume, every consultation is read the same day by a GPhC-registered prescriber, a named clinician, not automated software. If you would like to find out whether Wegovy is right for your situation, start your free consultation and our prescribers will review your details the same day.