Wegovy for weight loss: the evidence, the eligibility and what to expect

What the STEP 1 trial actually showed, and what it means for you

The headline figure most people encounter is 15%. That comes from the STEP 1 trial, a 68-week phase 3 study in adults with obesity or overweight and at least one weight-related condition, published in the New England Journal of Medicine. Participants taking semaglutide 2.4mg lost an average of around 15% of their body weight, compared with about 2.4% in the placebo group. That gap is substantial, and it's why regulators and NICE took the evidence seriously enough to grant approval and a positive recommendation respectively.

What the trial can't tell you is what your individual result will be. Weight loss varied considerably between participants. Lifestyle changes (a reduced-calorie diet and increased physical activity) were part of the protocol alongside the injection, and that context matters clinically. A question our prescribers hear most weeks is whether the medicine does the work on its own; the honest answer is that it reduces appetite strongly, but the habits you build alongside it shape the long-term outcome. You can read more about how semaglutide works as a medicine, including the full mechanism if you want that detail.

Since STEP 1, the programme has expanded. The MHRA approved a 7.2mg maintenance dose in January 2026, and then a dedicated single-dose 7.2mg pen on 14 April 2026. Early data reported around 20.7% average weight loss at that higher dose over 72 weeks, which narrows the gap with tirzepatide seen in the SURMOUNT-5 head-to-head trial.

Who Wegovy is licensed for, and the NHS criteria that catch far fewer people than you'd think

The UK licence covers adults with a BMI of 30 or above, or a BMI of 27 to 29.9 alongside at least one weight-related condition such as high blood pressure, high cholesterol, type 2 diabetes or obstructive sleep apnoea. Lower BMI thresholds apply for some ethnic backgrounds under UK guidance. Semaglutide is not licensed for under-18s, and it is not recommended during pregnancy, while breastfeeding, or when trying to conceive.

NICE's recommendation (TA875, published March 2023) is narrower than the licence. On the NHS, Wegovy is recommended only within a specialist weight management service, for a maximum of two years, and for adults with a BMI of 35 or above and at least one weight-related comorbidity, with thresholds 2.5 kg/m² lower for people of Asian, Chinese, Middle Eastern, Black African or African-Caribbean backgrounds. Waiting times for those specialist services can stretch to months or longer in many areas. Private prescribing follows the licensed criteria rather than the NICE commissioning thresholds, which is why many people who don't meet the NHS criteria are still clinically eligible through a regulated private pharmacy. The NICE appraisal of semaglutide (TA875) sets out the full NHS eligibility picture if you want to read it directly.

BMI alone never decides the outcome. A prescriber looks at your full clinical picture, any contraindications, current medicines and your weight history before approving treatment. That's true whether you approach the NHS or a private service like ours.

What the side effects profile looks like in practice

Semaglutide's side effects are well-documented at this point. The most common are gastrointestinal: nausea, vomiting, diarrhoea, constipation and indigestion are all reported, particularly at the start of treatment or after each dose increase. For most people these settle within days to a couple of weeks as the body adjusts. Starting low (the titration schedule begins at 0.25mg) is specifically designed to reduce how disruptive this period feels.

More serious but less common effects to know about include acute pancreatitis. Severe, persistent stomach pain that extends to the back, with or without vomiting, needs urgent medical assessment; don't wait to see if it passes. Gallbladder problems, dehydration from prolonged vomiting or diarrhoea, and allergic reactions are also listed in the prescribing information. The NHS medicines page for semaglutide covers side effects in patient-friendly language and is worth bookmarking alongside your patient information leaflet.

If you notice anything unexpected while on treatment, you can report it through the MHRA's Yellow Card scheme at yellowcard.mhra.gov.uk. Reporting matters, it's part of how post-market safety data is built for medicines still under additional monitoring, which Wegovy is, indicated by the black triangle symbol on its packaging.

Getting Wegovy through a regulated private pharmacy

Because these are prescription-only medicines, the only lawful route is a clinical consultation followed by a prescription from a registered prescriber. If you'd like to find out more about Wegovy before you take any steps, that's a good place to start. Through our Wegovy weight-loss service, the process runs like this: you complete a free consultation online, a GPhC-registered Independent Prescriber reviews it the same day, and if you're clinically suitable your treatment is dispatched the same working day for free next-working-day delivery via DPD, in plain unbranded packaging. No subscription, no auto-renewal, every repeat order is reviewed again before it goes out.

Cost is a fair consideration. If you want to understand how Wegovy weight loss works in practice, including what affects the price at different doses, it's worth understanding exactly what a quoted price includes. Some headline figures exclude the consultation, the prescription fee, delivery or aftercare support. The transparent approach (one price that covers everything) is what we think makes most sense for a prescription medicine where clinical oversight is the point, not an optional extra. If you're ready to see whether you qualify, you can start your free consultation here.