Most people who take the Wegovy injection get some side effects, but for the majority they are mild, digestive, and settle as the body adjusts. Knowing what is normal, what helps, and what needs attention takes a lot of the worry out of starting. This guide walks through all three. For the treatment overview, see our Wegovy treatment page.
The most common Wegovy side effects are digestive: nausea, diarrhoea, constipation and sometimes being sick. They are usually mild, tend to be worst in the first weeks and each time your dose steps up, and ease as your body adapts. Simple food and fluid habits help a great deal. Serious reactions are uncommon, but a few warning signs are worth knowing.
The common side effects
Wegovy is semaglutide, a GLP-1 medicine, and its side effects are typical of that group. The great majority are to do with digestion and are mild to moderate.
Why they happen
Semaglutide works partly by slowing down how quickly your stomach empties, which is exactly what helps you feel full for longer. The trade-off is that this same effect can leave you feeling queasy, bloated or off your food while your digestive system gets used to the new pace. That is why the effects are mostly in the gut, and why they tend to fade as your body adapts.
When side effects are most likely
There is a clear pattern to when they show up. They are usually at their strongest in the first few weeks of treatment, and again for a short spell each time your dose is increased, often peaking within the first two to four weeks of a new dose before settling. Wegovy is deliberately started low and stepped up slowly for this reason: the gradual build-up gives your body time to adjust and keeps the effects as manageable as possible. For most people they become much easier after the first couple of months.
How to manage them
Simple habits make a real difference, and most people find the early weeks very manageable with a few adjustments.
Serious side effects to watch for
These are uncommon, but it is worth knowing the signs so you can act quickly. Seek urgent medical advice if you have severe or persistent stomach pain, particularly if it spreads through to your back, as this can be a sign of pancreatitis. Ongoing vomiting that stops you keeping fluids down can lead to dehydration and needs attention. Signs of gallbladder problems, such as pain in the upper right abdomen, fever or yellowing of the skin or eyes, and any signs of a serious allergic reaction, also need prompt help. If you also take medicines for type 2 diabetes, be alert to low blood sugar. When in doubt, contact your prescriber, GP, NHS 111, or in an emergency call 999.
Side effects that are severe, persistent, or simply not improving are a reason to check in rather than push through. Often the answer is a small adjustment, such as holding a dose a little longer before stepping up, and that is a conversation your prescriber is there to have.
How we support you through them
You are not left to manage this alone. Our prescribers and pharmacists review how you are getting on at every refill, so if side effects are troubling you, we can talk through what helps and, where needed, adjust the pace of your dose increases. For a broader look at both treatments, our guide to Wegovy pill side effects covers the tablet version, and our Mounjaro side effects guide is useful if you are comparing options.
Frequently asked questions
What are the most common Wegovy side effects?
Nausea is the most common, along with diarrhoea, constipation, vomiting, indigestion and bloating. Headache, tiredness and dizziness can also occur. Most are mild and improve with time.
How long do Wegovy side effects last?
They are usually worst in the first few weeks and for a short period after each dose increase, often easing within the first couple of months as your body adapts. Everyone is different, so some settle sooner and some take a little longer.
Does Wegovy cause hair loss?
Some people notice temporary hair thinning, but this is usually linked to losing weight quickly rather than to the medicine directly. Keeping your protein intake up and avoiding very rapid weight loss helps, and it typically recovers.
Can I drink alcohol on Wegovy?
There is no absolute ban, but alcohol can worsen nausea and other digestive effects, and it adds empty calories. Many people find it best to limit it, especially in the early weeks. Ask your prescriber about your own situation.
What helps most with the nausea?
Smaller meals, eating slowly and stopping when full, going easy on rich or greasy food, staying hydrated, and not lying down straight after eating all help. Some people find ginger useful. If nausea is severe or stops you eating, speak to your prescriber.
When should I seek medical help?
Seek urgent advice for severe or persistent stomach pain, especially if it spreads to your back, for vomiting that stops you keeping fluids down, or for signs of an allergic reaction. Contact your prescriber or GP, call NHS 111, or in an emergency call 999.
Do side effects mean Wegovy is working?
Not necessarily. Side effects show your body is responding to the medicine, but they are not a measure of weight loss, and plenty of people lose weight with few side effects. The two do not reliably go together.
This guide is general information and not a substitute for personal medical advice. Wegovy (semaglutide) is a prescription-only medicine supplied after an online assessment and approval by a UK-registered independent prescriber. Always read the patient information leaflet and speak to your prescriber or pharmacist about any side effects.