What Is Wegovy? How It Works, How Well It Works and Is It Safe?

Wegovy is a prescription medicine for weight management that contains semaglutide. It works by copying a gut hormone, GLP-1, that helps control appetite. This guide explains what it is licensed for in the UK, how it works, what the main trials found and what to know about its safety, using the UK product information and the published trials.

What Is Wegovy?

A semaglutide medicine, licensed in the UK for weight management, cardiovascular risk reduction and MASH.

Wegovy contains semaglutide, a GLP-1 receptor agonist. It is made by Novo Nordisk and is licensed in the UK. It comes as a once-weekly injection from a FlexTouch pen, and also as a once-daily tablet with its own product information.

Its Summary of Product Characteristics (SmPC) licenses it, alongside a reduced-calorie diet and more physical activity, for:

• Weight management in adults with a body mass index (BMI) of 30 kg/m² or more, or 27 to 29.9 kg/m² with at least one weight-related condition.

• Weight management in adolescents aged 12 and over with obesity and a body weight above 60 kg.

• Reducing the risk of heart attack, stroke and cardiovascular death in adults with established cardiovascular disease and a BMI of 27 kg/m² or more.

• Treating MASH, a form of fatty liver disease with liver scarring, in adults with moderate to advanced fibrosis.

Semaglutide is also the medicine in Ozempic, which is licensed for type 2 diabetes at different doses.

How Does Wegovy Work?

It copies GLP-1, acting on appetite areas of the brain so people feel fuller and eat less.

Semaglutide is very similar to GLP-1, a hormone the gut releases after eating; the SmPC describes 94% sequence similarity. It works mainly on appetite:

• On the brain: GLP-1 receptors are found in brain areas that regulate appetite. The SmPC says semaglutide acts on areas that control how much we eat (in the hypothalamus and brainstem) and areas involved in the pleasure of eating.

• On eating: in an early trial, people on semaglutide 2.4 mg ate 35% fewer calories at a meal than people on placebo after 20 weeks, with more fullness, less hunger and fewer food cravings.

• On blood sugar: it helps release insulin and lowers glucagon when blood sugar is high, and slightly delays stomach emptying after meals.

Wegovy acts on GLP-1 only. Mounjaro acts on GIP as well; see how Mounjaro works.

How Well Does Wegovy Work?

In STEP 1, average weight change at 68 weeks was -14.9% with semaglutide 2.4 mg and -2.4% with placebo.

In STEP 1, published in the New England Journal of Medicine in 2021, adults with overweight or obesity and without diabetes took semaglutide 2.4 mg or placebo once a week for 68 weeks, alongside a reduced-calorie diet and more physical activity.

• The average change in body weight was -14.9% with semaglutide and -2.4% with placebo.

• 86.4% of people on semaglutide lost at least 5% of their body weight, against 31.5% on placebo.

For some adults with obesity, the dose can go up to 7.2 mg. The SmPC reports that in the STEP UP trials, weight loss at 72 weeks on 7.2 mg was superior and clinically meaningful compared with placebo.

These are averages across trials, not a prediction for one person. Results depend on the dose, how long someone stays on treatment and the diet and activity changes that go with it.

Wegovy and Heart Health

In SELECT, major cardiovascular events happened in 6.5% on semaglutide and 8.0% on placebo.

SELECT, published in the New England Journal of Medicine in 2023, followed 17,604 adults aged 45 and over with established cardiovascular disease, a BMI of 27 or more and no diabetes, for an average of about 3 years.

A heart attack, stroke or cardiovascular death happened in 6.5% of people on semaglutide and 8.0% on placebo, a hazard ratio of 0.80, which means about a 20% lower risk relative to placebo. The SmPC notes that the exact way it reduces cardiovascular risk has not been established.

Is Wegovy Safe?

It holds a UK licence; most side effects are stomach-related, with rarer serious ones such as pancreatitis.

Wegovy holds a UK marketing authorisation (PLGB 04668/0440), and its SmPC sets out the known side effects and warnings. The only contraindication it lists is an allergy to semaglutide or any of the other ingredients.

• Common side effects: most are in the stomach and gut, such as nausea, diarrhoea, vomiting and constipation, mostly while the dose is increasing. In STEP 1 they were typically mild to moderate and eased over time.

• Serious but uncommon or rare: acute pancreatitis, gallstones and gallbladder inflammation, and a rare eye condition called NAION. Seek immediate medical attention for persistent, severe stomach pain or sudden loss of vision.

• Stopping because of side effects: in SELECT, 16.6% of people on semaglutide stopped because of an adverse event, against 8.2% on placebo.

• Pregnancy and breastfeeding: Wegovy should not be used during pregnancy or breastfeeding, and should be stopped at least 2 months before a planned pregnancy.

Whether it is safe for you depends on your health and other medicines, which a prescriber checks before prescribing. For the full list, see Wegovy side effects. Report suspected side effects to the MHRA Yellow Card scheme.

How Is Wegovy Taken?

Once a week, starting at 0.25 mg and rising to 2.4 mg over 16 weeks.

The injection is taken once a week, at any time of day, with or without food, under the skin of the stomach, thigh or upper arm. It starts at 0.25 mg and goes up every 4 weeks to the 2.4 mg maintenance dose from week 17, and some adults with obesity then move to 7.2 mg. See our Wegovy dosage guide for the full schedule, or the Wegovy pill dosage guide for the tablet.

Who Can Get Wegovy?

A prescriber must check it is suitable; the licence covers adults with a BMI of 30+, or 27+ with a condition.

Wegovy is a prescription-only medicine, so a prescriber must check that it is suitable before it can be supplied. The licence covers adults with a BMI of 30 or more, or 27 or more with a weight-related condition.

On the NHS, NICE guidance TA875 recommends it within specialist weight management services for up to 2 years, for adults with at least one weight-related condition and a higher BMI threshold; access also depends on local commissioning and service availability.

Frequently Asked Questions