How well does Wegovy work — and is it the right decision for you?

The trial data: what a 15% average really means in practice

The STEP 1 trial is the cornerstone evidence for Wegovy at its standard 2.4mg maintenance dose. Nearly 2,000 adults without type 2 diabetes, with a BMI of 30 or above (or 27 and above with a weight-related condition), took part over 68 weeks. Those on semaglutide lost an average of about 15% of their body weight; those on placebo lost around 2.4%. The full STEP 1 paper, published in the New England Journal of Medicine, sets this out clearly.

An average of 15% is a population figure. In the same trial, roughly a third of participants lost more than 20%, and a smaller group lost less than 5%. Your biology, how consistently you take the medicine, and what you eat and do alongside it all pull the result in different directions. That spread is worth sitting with before making a decision.

The newer 7.2mg maintenance dose, approved by the MHRA in January 2026 and expanded with a dedicated single-dose pen in April 2026, narrows the gap with tirzepatide: trial participants at that dose achieved around 20.7% average weight loss over 72 weeks. If dose availability and the titration pathway for 7.2mg matter to your decision, that is exactly the kind of thing to raise with a prescriber at the consultation stage. You can read more about specific weight-loss outcomes by dose in our dedicated results guide.

What actually drives whether Wegovy works for a given person

The mechanism helps explain the variation. Semaglutide is a GLP-1 receptor agonist, and if you want to understand how semaglutide works at a molecular and physiological level, we cover that in detail separately. How Wegovy works at a physiological level is covered in detail separately, but the practical upshot is that the medicine makes eating less feel easier, it does not make it automatic.

Three factors consistently separate higher responders from lower ones in the trial data. First, consistency: missing doses, particularly in the early months, disrupts the steady-state concentration that the once-weekly schedule is designed to maintain. Second, lifestyle alongside treatment: STEP 1 participants had structured diet and activity support; the medicine was part of a package, not the whole of it. Third, individual biology: GLP-1 receptor sensitivity varies, and some people simply respond more strongly than others to the same dose. Our activity guidance for people on Wegovy covers how to build that second factor in practically.

Side effects also affect adherence, particularly in the first few weeks of treatment or after a dose increase. The most common are gastrointestinal: nausea, loose stools, constipation, and reflux. For most people these settle; for a minority they are enough to lead to dose reduction or stopping altogether, which in turn affects the weight outcome. Our prescribers are available seven days a week for aftercare, which matters most in those early weeks.

The eligibility question: who Wegovy is licensed to treat

NICE recommends semaglutide (Wegovy) under its TA875 appraisal for adults with a BMI of 35 or above and at least one weight-related comorbidity, used for a maximum of two years within a specialist weight management service. Private prescribing follows the licensed indication: adults with a BMI of 30 or above, or 27 and above with a qualifying condition such as hypertension, high cholesterol, or obstructive sleep apnoea. Lower thresholds apply for South Asian, Chinese, Middle Eastern, Black African and African-Caribbean backgrounds, in line with UK guidance. NICE's full recommendation (TA875) sets out the NHS eligibility criteria in detail.

BMI alone does not determine suitability. Wegovy is not recommended during pregnancy or breastfeeding, or for anyone planning to conceive; it is not licensed for under-18s; and a history of certain conditions, including pancreatitis or medullary thyroid carcinoma, requires careful prescriber review. The consultation exists precisely to work through that picture properly.

If cost is part of your thinking, what Wegovy costs through a private UK pharmacy is covered on our pricing page. Worth noting: Eli Lilly's list-price change in September 2025 moved the market for tirzepatide significantly, and Wegovy private pricing has shifted in the same period, so current figures are always best confirmed at the point of consultation rather than relied on from older sources.

Stopping treatment: what the evidence says about long-term use

A pattern the clinical literature is consistent about: weight tends to return when semaglutide is stopped, particularly without sustained lifestyle changes in place. The STEP 4 extension data showed that participants who discontinued after 20 weeks regained most of the lost weight within a year. This is not a failure of the medicine; it reflects that the biology driving weight gain does not disappear when treatment ends. It is also one reason NICE's TA875 recommendation specifies a maximum of two years in the NHS pathway, with ongoing assessment of whether continuing is appropriate.

For people considering Wegovy privately, this is part of the decision, not a footnote. A good consultation should address it honestly. Our semaglutide overview covers the broader clinical picture, and our clinical team are happy to take that question seriously at the assessment stage.

One practical note: many people start their consultation at the beginning of the month when it fits with their budget, or book after a holiday knowing they want a fresh routine in place. Whenever the timing works for you, the consultation is free and the clinical review happens the same day. Check your eligibility and start your free consultation to get a prescriber's view on whether Wegovy is the right fit.