Wegovy12 min read11 September 2026

Wegovy side effects: is it dangerous and what can you expect?

You are considering Wegovy or have just started, and online you read everything from "mild" to "life-threatening". You want to know what is really going on: how often do side effects occur, how long do they last and when is something wrong?

By Nagita Grover-Khatri

Medically reviewed by Nazanin Ahmadi Mozafari

White injection pen with a grey cap on a wooden table next to a sheet of paper with a graph

Consult

Is Wegovy dangerous? The short answer

Wegovy (semaglutide 2.4 mg) is a registered medicine that has been followed in studies in tens of thousands of people for up to more than four years. When used correctly, it is safe for most adults with overweight; the risks lie in rare side effects that a doctor needs to monitor, and in incorrect use: increasing the dose too quickly, without checks of the kidneys and pancreas, or with pens of unknown origin.

That is no reassurance to skip the patient information leaflet. The medication slows your stomach, changes your appetite and lowers your blood sugar. If you know that, you will recognise the complaints that come with it and the signals that are not normal. Read more about Wegovy vs Saxenda. Read more about Wegovy.

The most common side effects of Wegovy

The most common side effects of Wegovy are nausea, vomiting, diarrhoea, constipation, abdominal pain, headache and tiredness. They occur in more than 1 in 10 users, especially in the weeks when the dosage goes up. The Wegovy product information from the European Medicines Agency gives the figures from the registration studies (68 weeks) and the median duration per complaint.

Side effect	How often (leaflet)	In the studies (semaglutide vs placebo)	Median duration	What you do yourself	When to call the doctor
Nausea	Very common	43.9% vs 16.1%	8 days	Small portions, limit fatty and fried food, do not inject on an empty stomach	If you cannot keep anything down for more than a day
Diarrhoea	Very common	29.7% vs 15.9%	3 days	Drink enough, a little salt, rice and banana	With signs of dehydration or if it lasts longer than a few days
Vomiting	Very common	24.5% vs 6.3%	2 days	Small sips of water, rest, light food	With persistent vomiting or severe abdominal pain
Constipation	Very common	24.2% vs 11.1%	47 days	1.5 to 2 litres of water, fibre, daily exercise	If it does not improve after a week or with abdominal pain
Abdominal pain	Very common	19.7% vs 10%	Varies	Small meals, warmth	With severe, persistent pain that radiates to the back
Headache, tiredness	Very common	Mainly when the dose is increased	Days to weeks	Drink, eat regularly, sleep	If it lasts for weeks
Heartburn, belching, bloated feeling	Common	Mainly when the dose is increased	Days to weeks	Do not eat just before bed, avoid fizzy drinks	If antacids do not help
Dizziness, low blood pressure	Common		Short	Get up slowly, drink enough	If you faint
Faster heart rate	Common	On average 3 beats per minute higher	During use	Limit caffeine	With persistent palpitations at rest
Hair loss	Common	2.5% vs 1.0%	Usually recovers during use	Keep protein and nutrients up to level	If it does not stop
Gallstones	Common	1.6% vs 1.1%		Lose weight gradually	With pain in the upper right abdomen, fever or yellow skin
Injection site reactions	Common		Days	Rotate injection sites	If the area becomes warm, hard or painful
Pancreatitis	Uncommon	0.2% vs less than 0.1%		Nothing yourself: red flag	Immediately, with severe abdominal pain radiating to the back
Allergic reaction, angioedema	Rare			Nothing yourself: red flag	Immediately; if you are short of breath, call 112
Eye condition NAION	Very rare	About 1 extra case per 10,000 person-years of use		Nothing yourself: red flag	Immediately, if your vision suddenly gets worse

Very common means more than 1 in 10, common 1 to 10 in 100, uncommon 1 to 10 in 1,000, rare 1 to 10 in 10,000 and very rare less than 1 in 10,000. In the studies, the stomach and bowel complaints led 4.3 percent of users to stop. What you eat makes a big difference; the practical tips are in our article on an Ozempic diet plan, and they apply just as much to Wegovy.

Side effects per dose step: from 0.25 to 2.4 mg

The side effects follow the dosing schedule: each increase can temporarily bring back the nausea. You build up Wegovy over 16 weeks: 0.25 mg, 0.5 mg, 1 mg, 1.7 mg (4 weeks each) and then 2.4 mg as the maintenance dose.

0.25 mg (weeks 1 to 4): mild nausea and a full feeling after eating. Many users notice little yet; this is the dose for getting used to the medication, not the working dose.
0.5 mg (weeks 5 to 8): the nausea increases, often with belching. Diarrhoea or constipation may start.
1 mg (weeks 9 to 12): for many users, the peak of the stomach and bowel complaints and the point at which appetite clearly decreases. If you search for "Wegovy 1 mg side effects", this is the step most questions are about.
1.7 mg (weeks 13 to 16): the complaints usually level off; tiredness stands out because you eat less.
2.4 mg (from week 17): maintenance dose. In most users, the complaints have largely disappeared after 2 to 4 weeks on this dose.

If a step causes you a lot of trouble, the doctor can postpone the increase or go back a step until the complaints have eased; the product information explicitly allows for this. The full schedule is in Wegovy dosage.

How long do the side effects last?

Most side effects of Wegovy last days, not months. In the registration studies, the median duration of nausea was 8 days, of vomiting 2 days and of diarrhoea 3 days; constipation lasted longer, a median of 47 days. According to apotheek.nl (the patient information website of the Dutch pharmacists' organisation), nausea, diarrhoea, constipation and abdominal pain usually disappear within 4 weeks after a dose increase.

Because you increase the dose five times, the complaints can come back several times during the 16-week build-up phase. On the maintenance dose, the picture stabilises. If complaints persist after that, it is a reason to discuss the dosage or your eating pattern with the doctor, not to grit your teeth and carry on.

Tiredness, headache and eye complaints

Tiredness is listed in the product information as very common, especially in the build-up phase. It is usually caused by eating less and drinking less, sometimes by sleeping worse because of stomach complaints. Regular meals, protein and water help; if it lasts for weeks, have the doctor check your blood sugar and blood pressure.

Headache is also very common and is often linked to drinking too little. You can take paracetamol; if the headache persists or is unusually severe, call the doctor. On mood and low mood, the EMA concluded in April 2024 that the evidence does not support a causal link between GLP-1 medications and suicidal thoughts; still report any changes in your mood. There is more about this in Ozempic and depression.

Eyes: the European Medicines Agency (EMA) concluded in June 2025 that the eye condition NAION (a disorder of the blood supply to the optic nerve) is a very rare side effect of semaglutide: up to 1 in 10,000 users, about one extra case per 10,000 person-years of use. The advice: if your vision suddenly gets worse or deteriorates quickly, call the doctor immediately; if NAION is confirmed, you stop semaglutide. In people with diabetes, a rapidly falling blood sugar can also temporarily worsen an existing retinal condition. You can read what else is known in Ozempic eye problems.

Want to lose weight with medication, but worried about the side effects? With medical weight loss with injections, your own doctor builds up the dosage at your pace and is available if you have complaints →

Serious side effects: when do you call the doctor?

Call immediately if you have severe, persistent abdominal pain that radiates to your back, possibly with vomiting. That can be pancreatitis: 0.2 percent of users in the studies, rare but serious. Stop injecting until you have spoken to the doctor.

These signals are also a reason to get in touch the same day:

Pain in the upper right abdomen, especially after eating, with fever or yellow skin: gallstones or inflammation of the gallbladder (1.6 percent in the studies).
Persistent vomiting or diarrhoea with little urine, a dry mouth or dizziness: dehydration, with a risk to the kidneys.
Swelling of the face, lips or throat, shortness of breath or a rash: allergic reaction or angioedema. If you are short of breath, call 112.
Suddenly worse vision or a dark spot in your field of vision: have your eyes checked the same day.
Trembling, sweating, palpitations and hunger if you also use diabetes medication: low blood sugar.
Severe abdominal pain with a swollen abdomen and being unable to pass stools: a bowel obstruction, reported after registration, very rare.

Wegovy must not be used during pregnancy, when you are trying to conceive or while breastfeeding; how that works is explained in Ozempic and pregnancy. With a previous pancreatitis, severe kidney or liver problems, an eating disorder or medullary thyroid cancer in the family, the doctor also assesses whether the medication is suitable.

Long-term side effects: what do we know now?

More is known about the long term with semaglutide than with most new medications, because the substance has been on the market since 2018 and has been studied in large heart studies. In the SELECT trial (New England Journal of Medicine, 2023), 17,604 people with overweight and existing cardiovascular disease received semaglutide 2.4 mg or placebo for an average of more than three years. Serious cardiovascular events occurred in 6.5 percent of the semaglutide group and 8.0 percent of the placebo group. However, 16.6 percent of semaglutide users stopped because of side effects, compared with 8.2 percent on placebo, mainly because of stomach and bowel complaints.

No new types of side effects came to light during those years. Points of attention that the regulators continue to monitor are the very rare eye condition NAION (added in 2025), gallstones with rapid weight loss, muscle loss with too little protein and weight regain after stopping. The earlier concern about thyroid tumours comes from animal studies with much higher doses; in humans that link has not been demonstrated, but the doctor does not prescribe the medication if there is medullary thyroid cancer in the family.

You can read how the risks of the whole group of medications compare in our overview of GLP-1 side effects.

Side effects versus the risks of illegal products

Side effects with correct use are something different from the poisonings that make the news. The Nationaal Vergiftigingen Informatie Centrum (NVIC) (the Dutch Poisons Information Centre) of UMC Utrecht reported in June 2026 that the number of poisonings with weight loss medication doubled to 149 in 2025. In 40 percent of the reports about GLP-1 medications, no doctor was involved; there were also reports about retatrutide, a substance that is not registered in the Netherlands and is sold via social media.

The patterns behind those reports: pens or vials of unknown origin, self-dosing without a dosing schedule, and products that turn out to contain no semaglutide at all. These are not side effects of Wegovy, but risks of the illegal route. Legally, you can only get Wegovy on prescription from a doctor through a recognised Dutch pharmacy; our article on how to buy Wegovy explains how that works. With a medical weight loss with injections programme, the medication comes through a recognised pharmacy and if you have complaints you are in direct contact with your own doctor.

Want to know whether medical weight loss is right for you? Complete the eligibility check and the doctor will assess your situation →

Frequently asked questions about Wegovy side effects

How safe is Wegovy?

When used correctly under a doctor's supervision, Wegovy is safe for most adults with overweight. It has been followed in studies in tens of thousands of people for up to more than four years. Most side effects are short-lived stomach and bowel complaints; serious side effects such as pancreatitis are rare.

What are the serious side effects of Wegovy?

Pancreatitis (0.2 percent in the studies), gallstones and inflammation of the gallbladder, dehydration with kidney problems, allergic reactions, a very rare eye condition (NAION) and low blood sugar when combined with diabetes medication. Call immediately if you have severe abdominal pain radiating to the back, swelling of the face or throat, or suddenly worse vision.

What are the long-term effects of Wegovy?

In the SELECT trial (more than three years, 17,604 participants), no new types of side effects came to light and the number of serious cardiovascular events decreased. Points of attention remain gallstones, muscle loss with too little protein, the very rare eye condition NAION and weight gain after stopping.

Can Wegovy cause tiredness?

Yes, tiredness is very common, especially in the build-up phase. It is usually because you eat and drink less. Regular meals, protein and water help; if it lasts for weeks, have the doctor take a look.

How long can you use Wegovy?

No maximum duration of use has been set; Wegovy is registered for long-term use and has been studied for up to more than four years. The doctor periodically evaluates whether continuing makes sense, based on results and side effects.

What does Wegovy do to your body?

Semaglutide mimics the gut hormone GLP-1: it suppresses appetite, slows gastric emptying and lowers blood sugar when it is too high. Resting heart rate rises by an average of 3 beats per minute. You can read what users notice in Wegovy reviews.

Are the side effects of Wegovy different from those of Ozempic?

No, it is the same substance. Because Wegovy has a higher dose (2.4 mg compared with a maximum of 2 mg), stomach and bowel complaints occur slightly more often on the maintenance dose. The differences are set out in Wegovy vs Ozempic.

Responsible for this information: Qlinic B.V., Markenhaven 25A, Amersfoort. Published: 11 September 2026. This article is general information and does not replace personal medical advice.

About the author

Nagita Grover-Khatri

Doctor · BIG 39912467601

Focuses on medical programmes for overweight, with attention to the person behind the numbers.

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