Wegovy weight loss: what the medicine actually does and who it suits

You've heard the name everywhere, here's what Wegovy actually does in your body

Imagine finishing a modest lunch and feeling, genuinely, like you've eaten enough. That's the effect semaglutide is working towards. Wegovy mimics GLP-1, a hormone your gut releases after a meal, by binding to GLP-1 receptors in the brain and digestive system. The result is slower gastric emptying, a stronger sense of fullness, and quieter hunger signals between meals. It doesn't burn fat directly. What it does is make it easier to eat less, consistently, over months, which is where the weight loss comes from.

This mechanism is why the medicine is used alongside a reduced-calorie diet and increased activity rather than instead of them. The lifestyle changes do the work; Wegovy makes following through on them considerably more manageable for many people. You can read more about semaglutide and how it works if you want to go deeper on the pharmacology before deciding anything.

The medicine is given as a once-weekly subcutaneous injection, under the skin, typically in the abdomen, thigh or upper arm, rotating sites to avoid irritation. The pen itself is pre-filled and pre-set; there's no drawing up of medication, no measuring. A question our prescribers hear regularly is whether the injection is complicated. In practice, most people manage it comfortably by the second or third week.

What the trial evidence actually shows about Wegovy weight loss results

The headline figure from the STEP 1 trial (roughly 15% average body-weight reduction over 68 weeks at the 2.4mg maintenance dose) comes from a study published in the New England Journal of Medicine involving nearly 2,000 adults with obesity or overweight and at least one weight-related condition, without type 2 diabetes. That's not a small or short study.

Since that original approval, Novo Nordisk developed a higher dose. The MHRA approved a 7.2mg semaglutide dose in January 2026, and then in April 2026 cleared a dedicated single-dose 7.2mg pen, one injection per week, auto-set, with a covered needle that locks after use. Trials at 7.2mg reported around 20.7% average weight loss over 72 weeks, closing much of the gap with tirzepatide results. That pen is available for adults with a BMI of 30 or above; the titration still starts at 0.25mg and works up, because the dose increase schedule is designed to reduce side effects, not just reach the endpoint faster.

If you're weighing up how quickly to expect results, our page on how long Wegovy takes to work covers the realistic timeline month by month.

Who the licence actually covers, and what a clinical review adds on top

The licensed criteria are straightforward on paper: adults with a BMI of 30 or above, or a BMI between 27 and 29.9 with at least one weight-related condition such as high blood pressure, high cholesterol, obstructive sleep apnoea, prediabetes or type 2 diabetes. Lower BMI thresholds of 2.5 kg/m² apply for some ethnic backgrounds under UK guidance. The criteria for the 7.2mg pen apply only to those with a BMI of 30 or above.

Meeting those numbers, though, is where eligibility starts rather than where it ends. A prescriber's clinical review covers your medical history, current medicines, and anything in your background that would change the picture, a history of pancreatitis, certain thyroid conditions, or medicines that interact with slowed gastric emptying, for instance. Pregnancy, breastfeeding and trying to conceive are all situations where Wegovy is not recommended. Neither is use under the age of 18. None of those decisions belong on a tick-box form; they need a trained eye.

For a full look at how private access compares to NHS waiting lists, the guide to where Wegovy is available in the UK covers both routes honestly.

Side effects worth knowing about before you start

The most common side effects of Wegovy are gastrointestinal: nausea, constipation, diarrhoea, indigestion and burping feature consistently across the trial data and in real-world use. For most people they're strongest in the first weeks after starting or after a dose increase, and they settle. Fatigue, headache and injection-site reactions are also reported. The dose escalation schedule (starting at 0.25mg and moving slowly upward) exists specifically to reduce this burden.

Two things to know that sit above the routine list. First, the MHRA issued a Drug Safety Update in January 2026 flagging acute pancreatitis as a known but infrequent serious side effect across GLP-1 medicines: severe stomach pain that reaches into the back, with or without vomiting, warrants urgent medical attention, not a wait-and-see. Second, Wegovy carries a Black Triangle (▼) designation, meaning the MHRA is still actively collecting safety data, reporting anything unexpected via the Yellow Card scheme genuinely contributes to that monitoring. The NHS semaglutide medicines page has a full breakdown of common and rare effects worth reading before you start.

If cost is part of your thinking alongside all of this, our Wegovy cost and pricing guide explains what legitimate private treatment typically covers and why the price varies between providers.

If Wegovy sounds like it might suit your situation, the next step is a free consultation with our prescribers. Speak to our prescribers at the num treatment page, same-day clinical review, plain packaging, free next-working-day delivery once approved. You can also find a fuller picture of how Wegovy supports weight loss and what realistic outcomes tend to look like, or if you want a closer look at Wegovy as a weight loss medicine, including how it compares to other options, that page covers both in detail.