What is Wegovy and how does it work?

Wegovy is the brand name for semaglutide licensed for weight management — a once-weekly injection you give yourself under the skin. It mimics the gut hormone GLP-1, which reduces appetite, helps you feel full sooner and slows stomach emptying. The dose is increased gradually over several months to reduce nausea.

What are the side effects of Wegovy?

Stomach and bowel side effects are the most common, especially in the first weeks and after each dose increase. They include:

  • feeling sick or being sick
  • constipation or diarrhoea
  • feeling tired
  • itching or redness where you inject (redness can be harder to see on brown or black skin)
  • hair loss

These often ease with time. Talk to a pharmacist or the prescriber if a side effect bothers you or does not settle, and keep using Wegovy unless you are told to stop.

Serious side effects are rare. Call 111 or get urgent medical help for:

  • severe pain in your tummy or back that does not go away, which can be an inflamed pancreas (pancreatitis)
  • changes in your vision, including sudden loss of vision, or worsening diabetic eye disease
  • sweating, shaking, a pounding heartbeat and dizziness from low blood sugar, which is more likely if you also take other diabetes medicines

Call 999 for signs of a severe allergic reaction, such as a swollen tongue or throat, or difficulty breathing. If you feel dizzy or your vision changes, do not drive or use machinery until it has passed.

Who can get Wegovy on the NHS?

NICE recommends Wegovy for adults with:

  • a BMI of 35 or more — or 32.5 or more if you are of South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean background — and
  • at least one weight-related condition, such as type 2 diabetes, high blood pressure or obstructive sleep apnoea.

It is prescribed through specialist NHS weight-management services (not routinely by GPs), normally for up to two years, alongside diet and activity support. Separately, Wegovy can be prescribed without a time limit to reduce the risk of a further heart attack or stroke in people with cardiovascular disease who meet the criteria.

Wegovy is not Ozempic

Both contain semaglutide, but Ozempic is licensed in the UK for type 2 diabetes only, at lower doses. NHS weight-loss prescribing uses Wegovy. Be wary of anyone offering “Ozempic for weight loss” online — see is it safe to buy weight-loss jabs online?

How does Wegovy compare with Mounjaro?

In trials, semaglutide produced around 14% average body-weight loss, versus about 20% with Mounjaro (tirzepatide) — but the two have different NHS routes and criteria: Wegovy needs a lower BMI (35+) with one condition via specialist services, while Mounjaro’s GP route needs a BMI of 40+ with four conditions. Our weight-loss injections comparison covers both, plus Saxenda and availability across the UK nations.

Common questions about wegovy

What is the difference between Ozempic, Wegovy and Mounjaro?
All three are weekly injections, but they are not interchangeable. Ozempic (semaglutide) is licensed in the UK for type 2 diabetes only. Wegovy (also semaglutide) is licensed for weight loss. Mounjaro (tirzepatide) targets two gut hormones instead of one and led to more weight loss in trials — about 20% of body weight on average versus 14% with semaglutide.
Do you have to stay on weight-loss injections forever?
Weight loss from these medicines is maintained only while you keep taking them — most people regain weight after stopping. That is why NHS treatment always includes support with diet and physical activity alongside the injection, to build habits that help keep weight off if treatment ends. Your prescriber will review your progress regularly.
How do I get referred for Wegovy?
Ask your GP about a referral to an NHS specialist weight-management service. The service checks your BMI, weight-related conditions and medical history, and prescribes and monitors treatment if you qualify. Waiting lists vary by area. Wegovy is also used, without the two-year limit, to reduce the risk of a further heart attack or stroke in people who qualify.
What are the side effects of Wegovy?
The most common are nausea, vomiting, diarrhoea, constipation and reduced appetite, especially when the dose is being increased. These usually ease over a few weeks — smaller meals and less fatty food help. Rare but serious risks include pancreatitis and gallbladder problems. Contact your GP or 111 for severe or persistent symptoms, and seek urgent help for severe tummy pain.

Sources

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