The real pros and cons of Wegovy — what the evidence shows

The biggest misconception: that Wegovy 'does the work for you'

The most common misreading of the Wegovy evidence is that the injections replace the need for lifestyle change. They do not. In the STEP 1 trial, published in the New England Journal of Medicine, every participant followed a reduced-calorie diet and increased their activity alongside semaglutide. The ~15% average weight reduction is the product of both. The medicine reduces appetite and slows gastric emptying, which makes eating less considerably easier, but the calorie deficit still has to happen. People who expect Wegovy to work independently of diet tend to be disappointed. People who use it as a tool to support changes they are already trying to make often find it genuinely transformative. That framing matters before you weigh up the pros and cons of Wegovy, because the balance shifts depending on what you are actually expecting from treatment. You can read more about how semaglutide works on our dedicated page.

The genuine advantages, and why they hold up under scrutiny

On the pro side, the trial evidence for semaglutide is robust. The STEP 1 figures (around 15% average weight loss at 68 weeks, versus roughly 2.4% for placebo) come from a large, well-controlled randomised trial. For many people, that scale of weight reduction brings measurable improvements in blood pressure, cholesterol, blood sugar and joint load, benefits that extend beyond appearance. The MHRA has also authorised Wegovy to reduce the risk of major cardiovascular events in eligible adults, which is a meaningful additional indication. A higher-dose option now exists too: the 7.2mg single-dose pen, approved by the MHRA in April 2026, has been associated with around 20.7% average weight loss in trials, narrowing the gap with tirzepatide. Wegovy is also a once-weekly injection, which most people find manageable once the routine is established. And the pen itself is discreet, small, pre-set, used at home and returned to the fridge afterwards. When ordered through a regulated service, it arrives via tracked delivery in plain, unbranded packaging, with no indication of what is inside.

The real cons, side effects, titration and time

The semaglutide pros and cons conversation is dominated, understandably, by nausea. In the STEP 1 trial, nausea was reported by a substantial proportion of participants on semaglutide, particularly during the dose-escalation phase. Vomiting, diarrhoea, constipation and reflux are also common. For most people these effects are mild to moderate and settle over days to a couple of weeks after each step up, but for some they are significant enough to slow titration or, occasionally, to stop treatment. The titration schedule itself (moving from 0.25mg through several steps to the 2.4mg (or now 7.2mg) maintenance dose) takes months. Weight loss is gradual, not immediate. That timeline frustrates some people, but it also reflects how the medicine is designed to work safely. There is also the question of what happens if treatment stops: the evidence suggests that much of the weight lost returns over time without continued treatment or substantial lifestyle changes, which is worth factoring into any long-term plan. You can explore the cons of Wegovy in more detail in a dedicated piece.

Who this medicine is and is not suited to

Wegovy is licensed in the UK for adults with a BMI of 30 or above, or 27 or above alongside a weight-related condition such as high blood pressure, dyslipidaemia, obstructive sleep apnoea, cardiovascular disease or type 2 diabetes. Lower BMI thresholds apply for some ethnic backgrounds under UK clinical guidance. It is not licensed for people under 18, and it is not recommended during pregnancy, while breastfeeding, or when actively trying to conceive. People with a history of medullary thyroid carcinoma, multiple endocrine neoplasia type 2, or certain gastrointestinal conditions require particular prescriber care. The NICE appraisal for semaglutide (TA875) also sets conditions for NHS access (specifically, use within a specialist weight management service and for a maximum of two years) though private treatment through a regulated pharmacy follows the licensed criteria rather than those commissioning rules. The full picture of what makes Wegovy suitable or not is something our prescribers work through individually with each person, because BMI alone never tells the whole story. If you are thinking about the semaglutide pros and cons in the context of your own health, the right starting point is a clinical assessment rather than a checklist. A guide to accessing Wegovy in the UK sets out the legal route and what to expect at each stage. For a broader comparison of the weight-loss treatment options available, our treatment overview covers them all. When you are ready to talk to a prescriber, you can start your free consultation and have your answers reviewed the same day by a GPhC-registered Independent Prescriber.