Wegovy Side Effects UK
If you use Wegovy (semaglutide), expect most of the effects to sit in your stomach and gut: sickness, loose or hard stools and tummy pain, often with a headache and a tired feeling. They tend to show up soon after you start and again when the dose steps up, then fade for most people. Rarer problems do happen, and some need help the same day.
Get help now
Read this part first if you feel unwell after an injection.
999 now. Strong tummy pain that keeps going, particularly if it moves to your back, with or without being sick, can mean an inflamed pancreas. Also dial 999 if your lips, tongue, face or throat swell, you struggle to breathe or swallow, a rash spreads quickly, or you feel you may faint.
111 or your GP today. Pain high on the right side of your tummy with a temperature, yellow skin or eyes, or pale poo can point to the gallbladder. Call too if you cannot keep any drink down, you pass very little urine, or your sight suddenly changes.
Do not sit waiting on a chat message. If your provider only offers an online form or message, use 111 or 999 instead.
Is what I feel normal?
1 Mild and settling? A bit of sickness, loose stools or constipation in the first weeks, or after a dose increase, is expected. Tell your prescriber at your next check in. Keep injecting as planned unless they tell you otherwise.
2 Hanging around or stopping you eating or drinking? Speak to your prescriber or pharmacist. They can adjust things. If you are not sure how urgent it is, NHS 111 can help.
3 Severe, sudden or frightening? Treat it as an emergency. Use the section above.
Common side effects of Wegovy
The UK leaflet sorts side effects by how many people notice them. Here is that scale, matched to what you may feel.
|
How often |
In plain terms |
What the leaflet lists |
|---|---|---|
|
Very common |
More than 1 person in 10 |
Nausea, vomiting, diarrhoea, constipation, tummy pain, headache, tiredness |
|
Common |
Up to 1 in 10 |
Dizziness, hair loss, gallstones, soreness or redness at the injection site, indigestion, burping, wind, bloating, reflux, gastritis |
|
Uncommon |
Up to 1 in 100 |
Faster heartbeat, slower stomach emptying, kidney or bladder stones, inflamed pancreas |
|
Rare |
Up to 1 in 1,000 |
Severe allergic reaction |
Low blood sugar is more likely if you also have diabetes. Some bands depend on whether the medicine is used for diabetes or weight management, so read the current leaflet for your own case.
Stomach and gut
Sickness, diarrhoea, constipation, bloating, wind and burping all come from slower digestion. Small plain meals, eating slowly and steady sips of water help most people. Diarrhoea or sickness that stops you drinking needs a call to your prescriber, as you can dry out quickly.
Head and energy
Headache and tiredness are both in the very common group. They are not always caused by the medicine. Regular meals and enough fluid can ease them. Mention strong or lasting ones.
Hair, skin and injection site
Hair loss is on the common list and is often noticed during weight loss. Soreness, redness or itch where you inject is common and usually mild. Change the spot each week as the leaflet shows.
Gallbladder and kidneys
Gallstones are common and kidney or bladder stones are uncommon. Back or lower tummy pain, pain on passing urine, or dark urine are worth a same day call.
These tips are general. Your pharmacist or prescriber can tailor them. The leaflet is the final word on the medicine.
When do Wegovy side effects start, and how long do they last?
The dose goes up in steps, and side effects tend to follow the steps. Many people first notice something on day 1 or in the first week. Most stomach effects then calm down over the following weeks.
|
Stage |
What people tend to notice |
|---|---|
|
Day 1 and week 1 (0.25mg) |
A queasy or full feeling, some loose stools or a hard stool. Dizziness and headache can show up too. Mostly mild. |
|
Next steps (0.5mg and 1mg) |
The same effects can come back for a while after each increase, then ease. |
|
Higher steps (1.7mg and 2.4mg) |
Many people have settled by now. A repeat bout after a step is still possible. |
|
When it feels worst |
Usually in the weeks after starting and after a step up. |
|
If you miss an injection |
Follow the leaflet. Do not double up to make up for it. |
A rough week after a step up is not always a reason to give up. Your prescriber can pause on the same dose or go back a step. Do not alter the dose yourself.
Serious side effects of Wegovy
When people ask about the worst side effects, these are the ones. They are uncommon or rare, and the list is here so you can spot them, not because you should expect them.
Inflamed pancreas (uncommon)
Signs: Strong tummy pain that will not ease, often reaching the back, with or without sickness.
What to do: Stop using Wegovy and get urgent medical help.
Severe allergic reaction (rare)
Signs: Swelling of the face, lips, tongue or throat, difficulty breathing, a fast spreading rash.
What to do: Call 999.
This is not everything the leaflet lists, so read it in full.
Common worries about Wegovy side effects
Cancer. Thyroid tumours appeared in rats given semaglutide in studies. Nobody knows if the same happens in people. If you have had thyroid problems, or find a lump or swelling in your neck, tell your prescriber.
Eyes. People with diabetic eye disease should say so before starting. Painless sudden loss of vision is very rare, but needs a doctor straight away.
Liver. The leaflet does not list liver damage among the main side effects. Yellow skin or eyes with pale poo can come from the gallbladder, so ask for advice the same day.
Low mood. The leaflet does not list depression as a side effect. If your mood drops or you feel anxious, tell your GP or prescriber. If you think about harming yourself, call 999 or ring Samaritans free on 116 123.
Heart and blood pressure. The leaflet mentions a faster heartbeat and dizziness when you stand up quickly, both uncommon. Rise slowly, keep drinking, and report any fainting.
Alcohol. There is no alcohol rule in the leaflet. A drink can worsen sickness, dizziness and dehydration, so ask your prescriber what suits you.
Long term side effects of Wegovy
Wegovy is newer than many medicines, so the record over many years is still being built. Gallstones and hair thinning can turn up during treatment as weight falls. If something new starts or does not go away, tell your prescriber and file a Yellow Card report.
Side effects in different people
Wegovy side effects in women
The leaflet lists the same side effects for everyone, but adds advice on pregnancy. Use contraception while on Wegovy, and stop it at least two months before trying for a baby. Tell your prescriber if you are pregnant or breastfeeding.
Wegovy side effects in men
The leaflet gives men no separate list. What is on this page applies to men too.
Side effects linked to weight loss
Losing weight itself raises the chance of gallstones, and hair thinning is often noticed as weight comes off. Pain high on the right of your tummy is worth a call to your prescriber.
Wegovy side effects on the skin
Itching or redness at the injection site is common and mild for most people. Hair loss is also common. A fast spreading rash with swelling or breathing trouble is an emergency, so dial 999.
Report a side effect
Anyone can report a suspected side effect to the MHRA through the Yellow Card scheme, including patients and carers. Get well first, then report.
FAQs
Sources
- Wegovy summary of product characteristics and patient information leaflet, electronic medicines compendium
- NHS 111 — when to use it, and how
- MHRA Yellow Card scheme — reporting a suspected side effect
- Background on the medicine itself: What is Wegovy (Semaglutide)?
- Compare with Mounjaro side effects