Wegovy described: what this medicine is and how it works in practice

What exactly is semaglutide and why does it affect appetite?

Semaglutide is a synthetic version of a hormone your gut releases naturally after eating, called GLP-1 (glucagon-like peptide-1). In normal physiology, GLP-1 travels to the brain and signals that you have eaten enough. It also slows gastric emptying slightly, so food stays in the stomach longer and fullness lingers. The version in Wegovy is engineered to survive in the body for roughly a week, which is why a single weekly injection can sustain those effects continuously rather than in a short burst after each meal.

This mechanism is well-documented. The NHS medicines page for semaglutide explains that the medicine works on receptors in the brain involved in appetite regulation. The result for most people is that portion sizes that once felt modest begin to feel sufficient, and the pull toward snacking between meals diminishes. That shift in appetite is gradual, not a sudden switch, and it works alongside the lifestyle changes your prescriber will discuss with you rather than replacing them.

It is worth being clear about one thing that causes genuine confusion: semaglutide is sold under two brand names in the UK. Wegovy is the one licensed for weight management. Ozempic is also semaglutide, but it holds a separate licence for type 2 diabetes — it is not the same product for weight-loss purposes, and the two should not be interchanged. You can read more about the broader semaglutide landscape on our semaglutide overview page.

Who does the UK licence say Wegovy is for?

Wegovy is licensed for adults with a BMI of 30 or above, or a BMI of 27 to 29.9 where at least one weight-related health condition is present. Examples of qualifying conditions include high blood pressure, type 2 diabetes, raised cholesterol and obstructive sleep apnoea. Lower BMI thresholds may apply for people from certain ethnic backgrounds under UK guidance. A prescriber determines suitability by looking at the whole picture: current health, medication list, medical history and individual circumstances, not the BMI number alone.

A question our prescribers hear most weeks is whether Wegovy is suitable for someone who has already tried other approaches without success. The honest answer is that eligibility is clinical, not a reward for effort. If the BMI and health criteria are met and there are no contraindications, the starting point is an assessment, not a prior track record of failed diets.

Wegovy is not recommended during pregnancy, breastfeeding, or for those actively trying to conceive. It is not licensed for use in under-18s. If you want to understand the full eligibility picture, our page on prescribing Wegovy covers the clinical criteria in more detail. The NICE technology appraisal TA875 sets out the NHS recommendation criteria, which are narrower than the licensed indications and come with a two-year NHS maximum duration.

What does a real course of treatment look like from week one?

Treatment begins at 0.25 mg once a week. This dose is deliberately low, its purpose is to let the body adjust to the medicine rather than to produce meaningful weight change. Most prescribers move through the schedule at roughly four-week intervals: 0.25 mg, then 0.5 mg, then 1.0 mg, 1.7 mg, and finally the standard 2.4 mg maintenance dose. Since January 2026, a higher 7.2 mg maintenance option has been available for eligible adults, following MHRA approval, most recently with a dedicated single-dose pen approved in April 2026.

The injection itself goes just under the skin, at the abdomen, thigh or upper arm, rotating sites each week. Most people find the device straightforward to use. Storage is in the refrigerator, though there is a limited window for room-temperature storage, your Patient Information Leaflet gives the exact figures for that, and it is worth reading before you travel. For practical information on how a prescription is arranged, see our page on getting a Wegovy script.

It is also worth knowing that the STEP 1 trial, published in the New England Journal of Medicine, found an average body-weight reduction of around 15% over 68 weeks at the 2.4 mg dose, among adults without diabetes. That figure comes from a controlled trial setting; individual results vary and depend on adherence, diet and activity alongside the medicine. For a sense of what treatment costs privately, our Wegovy price page explains how UK pricing works in practice, including whether a Wegovy subscription or getting Wegovy without a subscription is the more practical arrangement for your situation.

What side effects are most commonly reported with Wegovy?

The most frequently reported side effects are gastrointestinal: nausea, loose stools, constipation, indigestion and burping are all listed. Fatigue and headache are also noted. These effects tend to be most noticeable in the first couple of weeks after starting or stepping up to a higher dose, and they ease for most people as the body adapts. Eating smaller portions and avoiding rich or fatty food during the early weeks can help.

Some side effects require prompt medical attention. Severe stomach pain that does not pass, especially if it radiates toward the back with or without vomiting, should not be waited out at home. In January 2026 the MHRA issued guidance specifically flagging acute pancreatitis as an infrequent but potentially serious effect of GLP-1 medicines. Signs of a gallbladder problem, significant dehydration, or any allergic reaction also warrant urgent review. The MHRA Yellow Card scheme allows patients to report suspected side effects directly, and doing so helps build the safety evidence base for medicines like Wegovy.

If you are thinking about starting treatment and want to understand the process from consultation through to delivery, our weight-loss treatment overview is a good starting point, and our team is available seven days a week for aftercare questions once you are under our care.