Written and medically reviewed by W. van Donselaar, doctor, BIG 79020681301, on 16 June 2026.
Wegovy often causes side effects, particularly in the first few weeks and whenever the dose is increased. Most are mild and resolve on their own. Stomach and gut complaints are the most common. A small number of people experience these for longer. An even smaller number experience a rare, serious side effect requiring urgent medical attention. You can read below about what symptoms there are, how often they occur, what you can do about them yourself, and when to contact your doctor.
What side effects occur?
The patient information leaflet categorises side effects according to how common they are. For Wegovy, this is as follows:
| How often | Update |
|---|---|
| Very often (more than 1 in 10) | Nausea, diarrhoea, vomiting, constipation, abdominal pain, headache, fatigue |
| Frequent (1 in 100 to 1 in 10) | Dizziness, gastroenteritis, heartburn, belching, flatulence, changes in taste, hair loss, reactions at the injection site |
| Sometimes (1 in 1,000 to 1 in 100) | Inflammation of the pancreas, gallstones, kidney complications, increased heart rate, worsening of diabetic retinopathy |
| Rarely | Severe allergic reaction |
| Very rarely | Specific eye condition (NAION) in recent reports; link still under investigation |
Gastrointestinal symptoms are therefore by far the most common. Nausea tops the list. In clinical trials, around four in ten participants reported nausea during the build-up phase. The rest did not, or experienced it in a milder form.
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Why exactly stomach and intestines?
Semaglutide, the active ingredient in Wegovy, slows down gastric emptying. Food leaves your stomach more slowly than you are used to. This helps you feel full, but it can also cause nausea and stomach ache. You will notice this particularly after large or fatty meals.
In the build-up phase, your body is not yet used to that new rhythm. This is why symptoms are strongest in the first weeks. And again when the dose goes up. For most people, the symptoms diminish within two to four weeks on a stable dose.
Wegovy has a long titration schedule, increasing in steps from 0.25 mg to 2.4 mg per week. Each step lasts at least four weeks. This is deliberately gradual. Increasing the dose too quickly increases the risk of side effects before your tolerance has had a chance to build up.
What can you do yourself?
A few practical adjustments help a lot:
- Eat smaller portions, more often a day.
- Avoid fatty, heavy or highly spiced meals in the first weeks.
- Stop eating as soon as you feel full, even if your plate is not yet empty.
- Drink small sips of water, spread throughout the day.
- Take a short walk after dinner.
Specifically for nausea, ginger tea, dry crackers and light meals work well. Avoid alcohol in the build-up phase; it intensifies symptoms.
If you have persistent diarrhoea, make sure you drink plenty of fluids and eat easily digestible foods (rice, bananas, toast). Avoid dairy products and strongly spiced dishes for one to two days. If you are constipated, fibre, water and regular exercise can help.
When do you call your doctor?
Most side effects are unpleasant but not dangerous. If you experience any of the following symptoms, you should contact your doctor or the out-of-hours GP service immediately:
- Persistent, severe abdominal pain, possibly radiating to your back. This may indicate inflammation of the pancreas.
- Signs of gallstones: severe pain in the upper right of your abdomen, especially after eating fatty foods, sometimes with yellowing of skin or eyes.
- Suddenly seeing worse, or a loss of part of your field of vision. This could be a sign of the rare eye condition known as NAION.
- Signs of a severe allergic reaction: swelling of face, lips, tongue or throat, difficulty breathing, severe rash.
- Signs of dehydration due to persistent vomiting or diarrhoea: little urination, dry mouth, dizzy when standing up.
When in doubt: better to call than escalate a complaint.
When combined with other medications
Taking Wegovy alongside other medicines changes the side-effect profile. Two combinations require particular attention. When taken with insulin or other blood-sugar-lowering medicines, the risk of low blood sugar increases. Your doctor will often reduce the dose of the other medicine. Never adjust your insulin dose yourself when starting Wegovy. If you are taking medicines that affect your kidneys or cause fluid loss, your doctor will monitor your kidney function more closely, especially if you lose a significant amount of weight.
During an intake, we map out all your medication and assess where adjustment or additional monitoring is needed. Do you use oral contraception? Due to slower gastric emptying, intake may change slightly, although this is rarely clinically relevant.
Do the check if you’d like to find out whether a guided programme with Wegovy is right for you and how we’ll monitor your progress together during the first few weeks.
Do the side effects outweigh the effect?
For most people, this is the case, as the symptoms subside after a few weeks and the desired effect is achieved. For a minority, however, the symptoms remain too burdensome. In clinical trials, some participants drop out early, often due to side effects or a lack of efficacy.
A few questions can help you weigh up the options. On a scale of one to ten, how severe are your symptoms? How much do they affect your daily life? What alternatives have not yet been tried? Consider a lower maintenance dose (1.7 mg instead of 2.4 mg), a slower titration, or a different medication. And which lifestyle changes are you already making, and which not yet? We discuss this during the review appointments. Anyone experiencing persistent severe symptoms may, in consultation with the doctor, remain on a lower maintenance dose. A permanently lower dose is less effective, but if well tolerated, this is sometimes better than stopping.
For product information such as composition, contraindications and storage see the Wegovy page in our medication guide. For a guided route with Wegovy injections which includes routine monitoring for side effects, you can book an initial consultation.
Key points blog
How common are the side effects of Wegovy?
How common are the side effects of Wegovy?
Gastrointestinal complaints are the most common. Nausea, diarrhoea, vomiting and constipation are very common: in more than one in 10 users, according to the package leaflet. They occur mainly in the first two to four weeks and around each dose increase.
What is NAION, and is it a cause for concern?
What is NAION, and is it a cause for concern?
NAION is a specific eye condition characterised by a sudden loss of vision. In 2025, the European Medicines Agency confirmed this as a very rare side effect of Wegovy and other semaglutide-based medicines. If you experience sudden vision problems, contact a doctor immediately.
Do side effects disappear on their own?
Do side effects disappear on their own?
Usually, yes – within two to four weeks, once your body has adjusted. After each increase in dose, you may experience another mild bout of symptoms, though this is also temporary. If it persists, discuss it with your doctor. Increasing the dose more gradually or staying on a lower maintenance dose may help.