Knowing what to expect before you start makes the first weeks easier, and makes it easier to tell an ordinary side effect from one that needs help. Most Wegovy side effects are gut related, most often appear while your dose is going up, and settle as your body adjusts.
What are the most common side effects of Wegovy?
Most Wegovy side effects are gut related and settle as your body adjusts. Headache, nausea, vomiting, diarrhoea, constipation, stomach pain and tiredness affect more than 1 in 10 people. Indigestion, reflux, burping, wind, bloating, dizziness, altered skin sensation, hair loss, gallstones and injection site reactions are common. Altered skin sensation and hair loss may happen more often at the 7.2mg dose.
| How common | Side effects |
|---|---|
| Very common (more than 1 in 10) | Headache, nausea, vomiting, diarrhoea, constipation, stomach pain, tiredness |
| Common (up to 1 in 10) | Indigestion, reflux, burping, wind, bloating, dizziness, altered skin sensation, hair loss, gallstones, injection site reactions |
The full list is in the patient information leaflet in your pack.
How often do stomach side effects happen?
In the four main trials in the UK product information, over 68 weeks on Wegovy 2.4mg, nausea affected 43.9% of people compared with 16.1% on placebo, diarrhoea 29.7% compared with 15.9%, vomiting 24.5% compared with 6.3%, and constipation 24.2% compared with 11.1%. Most of these were mild to moderate and short-lived, and they were reported most often while the dose was being increased. Stomach side effects led 4.3% of people to stop treatment for good. Individual results vary.
Why does Wegovy cause nausea?
Wegovy slows how quickly your stomach empties. Food stays in your stomach for longer, which helps you feel full, but it can also feel like having eaten too much. Nausea is most likely in the weeks after a dose increase, which is why the dose starts low and goes up gradually: it makes stomach side effects less likely. Our Wegovy dose schedule explains each step.
How can you manage nausea and other stomach side effects?
- Eat smaller meals. Smaller portions are easier to manage while your stomach empties more slowly. Stop when you feel full.
- Avoid very fatty food. Rich, greasy meals stay in the stomach longest.
- Keep well hydrated. Sip fluids through the day, and more if you are being sick or have diarrhoea, as dehydration can affect your kidneys.
- Avoid alcohol where you can. The NHS advises that it is best not to drink alcohol on semaglutide, because it can make feeling or being sick worse.
- Do not rush a dose increase. If a step is hard, tell your pharmacist. The product information allows staying on your current dose for longer, or going back to the previous dose until symptoms improve.
What helps with constipation on Wegovy?
Constipation is very common and can last longer than the other stomach side effects. The NHS advice is to drink plenty of water and other fluids, gradually add more fibre to your diet, and be more active: a daily walk can help. If it does not improve, speak to your pharmacist about a suitable laxative. The leaflet also lists bowel obstruction, a severe form of constipation with other symptoms: get medical help promptly if constipation is severe or comes with stomach pain, bloating or vomiting.
Can Wegovy make you tired or dizzy?
Yes. Tiredness affects more than 1 in 10 people, and dizziness is common. They usually ease with time. If you feel dizzy or have problems with your vision, do not drive, ride a bike or use machinery until it has passed. If you have type 2 diabetes and use insulin or a sulfonylurea, know the signs of low blood sugar (sweating, shaking, sudden hunger, confusion) and treat it promptly.
Does Wegovy cause hair loss or tingling skin?
Both are common. Hair loss and altered skin sensation, such as tingling or a mild burning feeling, may happen more often at the 7.2mg dose, and the change in skin sensation usually goes away over time. Tell your pharmacist about either, especially before a dose increase. Our guide to Wegovy 7.2mg covers the higher dose in more detail.
What about injection site reactions?
Redness, itching or bruising where you inject is common. Use a different spot each week: you can use the same general area, but not the exact spot you used last time. Our guide on how to inject Wegovy covers the injection sites and technique.
What are the serious side effects of Wegovy?
These are less common, but you should know the signs. The "When to see your pharmacist or doctor" box below says exactly what to do.
- Pancreatitis (inflamed pancreas), uncommon, up to 1 in 100 people: severe stomach pain that does not go away, sometimes spreading to your back, with or without being sick. Stop Wegovy and get urgent medical help.
- Gallstones, common, up to 1 in 10 people: pain in the upper right of your tummy, fever, or yellowing of the skin or eyes.
- Kidney or bladder stones, uncommon: pain in your back or lower tummy, difficulty passing urine, or a change in the colour of your urine.
- Dehydration from vomiting or diarrhoea, which can affect your kidneys.
- Diabetic eye disease, common in people with diabetes: tell us or your doctor about any change in your vision.
- A sudden loss of vision from a problem with the optic nerve (NAION), very rare, up to 1 in 10,000 people: get your eyes checked the same day.
- A severe allergic reaction, rare: swelling of the face or throat, or difficulty breathing. Call 999.
Is it safe to have an operation while on Wegovy?
Before any operation: tell your surgical or anaesthetic team you take a GLP-1 medicine. It slows stomach emptying, which matters for anaesthesia.
What about pregnancy?
Pregnancy: these medicines must not be used in pregnancy. Stop and contact us or your GP immediately if you become pregnant. If planning pregnancy: stop Mounjaro at least 1 month before, Wegovy at least 2 months before.
How do you report a side effect?
Tell your pharmacist about any side effect that worries you, and report suspected side effects to the MHRA through the Yellow Card scheme. For how to store your pens safely, see Mounjaro and Wegovy storage. If you are moving between medicines, read switching between Mounjaro and Wegovy.