Will Wegovy make you lose weight — and by how much?

What STEP 1 found, and why the numbers need context

The STEP 1 trial enrolled 1,961 adults with obesity or overweight and at least one weight-related condition. After 68 weeks, those on semaglutide 2.4mg lost an average of about 14.9% of their starting weight, compared with roughly 2.4% in the placebo group. Around two thirds of participants lost at least 10% of their body weight. Those are population averages, not a floor, some people lost considerably more, others less. The NHS medicines page for semaglutide reflects this nuance: the medicine supports weight loss, it does not guarantee a specific figure for any individual.

What also matters is that the trial participants received structured lifestyle support alongside the injection. Wegovy is licensed as an adjunct to a reduced-calorie diet and increased physical activity, not as a standalone treatment. The medicine quiets appetite; what you do with that quieter appetite still shapes the result. If you want a closer look at how individual responses play out in practice, the question of whether Wegovy will work for you personally explores that in more detail.

How semaglutide produces weight loss, the biology in plain terms

Semaglutide mimics a hormone called GLP-1 that is released naturally after eating. It binds to receptors in the hypothalamus, the brain region that governs hunger and satiety, reducing the drive to eat. It also slows gastric emptying, so food sits in the stomach longer and fullness arrives sooner. Both effects work together to produce a sustained reduction in calorie intake without the person having to fight hunger through willpower alone. If you are wondering whether semaglutide will help you lose weight, understanding how this hormonal mechanism works in practice is a good place to start. This is why semaglutide represents a different category of treatment from older appetite suppressants: the mechanism is hormonal, not stimulant-based.

The dose is built up gradually (starting at 0.25mg weekly and increasing through several steps to the 2.4mg maintenance dose) partly to allow the body to adjust, which reduces early nausea. Most of the weight loss happens progressively over the first year, and the medicine continues to support weight maintenance if treatment is ongoing. For a more granular picture of the timeline, the page on how soon weight loss typically starts on Wegovy covers the week-by-week pattern in detail.

Who the evidence applies to, eligibility and honest expectations

The licensed indication for Wegovy covers adults with a BMI of 30 or above, or a BMI of 27 to 29.9 with at least one weight-related condition such as high blood pressure, type 2 diabetes, high cholesterol or obstructive sleep apnoea. Lower BMI thresholds apply for some ethnic backgrounds under UK guidance. A prescriber reviews the full picture (other medicines you take, your medical history, and your goals) before any prescription is issued.

It is also worth being clear about who the evidence does not apply to. Wegovy is not licensed for people under 18, and it is not recommended during pregnancy, while breastfeeding, or for those actively trying to conceive. The clinical decision on whether it is appropriate for you sits with a prescriber, not with a search result. If you are thinking about cost as part of the picture, the Wegovy pricing page sets out what legitimate private treatment typically involves. Our free consultation is the practical next step if you want a clinician's view of your own situation.

Side effects and what to watch for

The most common effects reported in the STEP 1 trial were gastrointestinal: nausea, vomiting, diarrhoea, constipation and indigestion. These were mostly mild to moderate and tended to ease after the body had time to adjust at each dose level. They are worth anticipating rather than fearing, for many people they are mild enough not to interrupt daily life, and they typically settle as the weeks go on.

Some effects warrant prompt medical attention. Severe stomach pain that radiates to the back can be a sign of pancreatitis, which the MHRA highlighted in a January 2026 Drug Safety Update on GLP-1 medicines. Gallbladder symptoms, signs of dehydration following persistent vomiting or diarrhoea, and any allergic reaction also need same-day medical review. People sometimes also notice unexpected changes in mood or libido while on treatment, and if that is something on your mind, the page on whether Wegovy affects sex drive looks at what the evidence does and does not show. The reporting tool for suspected side effects is the MHRA Yellow Card, which patients can use directly. Your prescriber and the patient information leaflet supplied with your pen are the right source for personalised guidance on managing effects, not a dose-by-dose account from an article. When your pen does arrive, it comes by DPD the next working day in plain, unbranded packaging; the tracking notification gives you a delivery window so the pen goes straight into the fridge when it lands.