The real risks of Wegovy — what patients are told, and what they aren't

The moment most people actually Google 'Wegovy risks'

You've probably just been told you're suitable for Wegovy, or you're a week or two into treatment and your stomach is reminding you loudly that something has changed. That's the honest picture of when most people search this. Feeling unsettled about it is reasonable. These are real medicines that work on gut-hormone pathways, and your body notices.

The NHS semaglutide medicines page lists the common side effects as nausea, vomiting, diarrhoea, constipation, indigestion, reflux, burping, fatigue and headache. None of that is small print. In the STEP 1 clinical trial, most participants on semaglutide 2.4mg reported at least one gastrointestinal symptom during the 68-week study, and this is the pattern in real-world use too. The symptoms are usually worst in the first weeks and after each dose step up, then they settle. Eating smaller portions, staying hydrated and not eating right before your injection can help. Your prescriber and the Patient Information Leaflet in the box both carry specific guidance on managing this, that's the right place to go, not a forum.

Our prescribers at nume, sorry. Our prescribers at nume hear this question most weeks: 'Is it supposed to feel this rough at the start?' Usually, yes. That doesn't make it comfortable, but it does usually pass.

The risks that need proper clinical attention

Beyond the expected GI discomfort, the risks with Wegovy that require genuine medical attention fall into a smaller category. The most clinically significant is acute pancreatitis. In January 2026 the MHRA published a Drug Safety Update for GLP-1 medicines confirming pancreatitis as a known, though infrequent, risk. The warning sign is severe stomach pain that comes on persistently and may spread to your back, with or without vomiting. If that happens, stop the injection and seek urgent medical help. Do not wait to see if it settles.

Other side effects worth knowing: gallbladder problems (gallstones, cholecystitis) have been reported in people on semaglutide. Dehydration from persistent vomiting or diarrhoea can strain the kidneys. A small number of people experience mood changes or low mood, if thoughts of self-harm arise, treat this as urgent and contact a healthcare professional or crisis service immediately. Allergic reactions, including swelling of the face or throat, are rare but serious and need 999.

People with a personal or family history of medullary thyroid carcinoma or MEN2 syndrome should not take semaglutide, this is a firm contraindication. Our page on the risks of taking Wegovy covers how these considerations differ in people with a history of pancreatitis or significant gastrointestinal disease, since your prescriber weighs these individually. For a fuller picture of how the medicine works and who it suits, our Wegovy overview covers the licensed basis in detail.

Risks specific to contraception, pregnancy and certain life situations

The MHRA advises using contraception while on Wegovy and for a wash-out period after stopping before trying to conceive. Wegovy is not recommended during pregnancy or while breastfeeding, and is not licensed for anyone under 18. If you want to understand semaglutide risks and side effects around contraception more fully, it is worth noting that the injectable form does not carry the same theoretical concern about oral contraceptive absorption as tirzepatide does, but MHRA guidance still recommends reliable contraception throughout treatment. If you become pregnant while taking Wegovy, stop the medicine and speak to your GP or midwife promptly.

Surgery is another situation that warrants care. Tell the anaesthetist and surgical team that you are on Wegovy before any procedure, GLP-1 medicines slow gastric emptying, which can affect anaesthetic safety. NHS England's guidance on weight-management injections covers this and the contraception advice clearly, and is worth reading alongside your Patient Information Leaflet.

The long-term risk profile of semaglutide for weight management is an area of ongoing research, and our dedicated page on semaglutide risks covers both the established evidence and the questions that researchers are still working to answer. What we know from the STEP trials and post-marketing data is reassuring on cardiovascular outcomes for eligible patients, but the long-term risks of Wegovy page goes into more depth on that evidence as it develops.

When to get medical help, and how to report a side effect

This is worth being direct about. Seek urgent medical help if you develop: severe persistent abdominal pain, especially radiating to the back (possible pancreatitis); signs of a serious allergic reaction such as face or throat swelling or difficulty breathing; severe dehydration from vomiting or diarrhoea that you cannot manage at home; sudden changes in vision; or thoughts of self-harm. These are not common, but they are the risks where delay has real consequences.

For side effects that are uncomfortable but not urgent, your prescriber is the right first call. At nume, priority aftercare is available seven days a week, you're not left to manage things alone after your prescription is issued.

You can also report any suspected side effect from Wegovy directly to the MHRA through the Yellow Card scheme at yellowcard.mhra.gov.uk. Patient reports are how regulators identify patterns that clinical trials miss, so it genuinely matters. The same reporting route is available if you suspect a counterfeit or substandard medicine.

If you're still weighing up whether Wegovy is right for you, our page on Wegovy risks and side effects has more detail, and our prescribers discuss individual suitability and these risks as a standard part of the free consultation. You can start that consultation here.