What are the main side effects of Wegovy?

Wednesday, September 30, 2026

Wegovy can cause side effects, particularly when you start treatment or increase your dose. The most common are nausea, diarrhoea, vomiting, constipation, stomach pain, headaches and tiredness (1-3).

In clinical trials, most digestive side effects were mild to moderate and short-lived, although constipation tended to last longer (4-6). There are also some less common but potentially serious side effects to know about, including pancreatitis and severe allergic reactions (2,3,7).

This guide explains what Wegovy side effects you might experience with the injection or pill, what you can do to make them more manageable, and when a symptom may need medical attention.

Learn more about Wegovy injections or the Wegovy Pill from Oxford Online Pharmacy.

In this article:

What are the most common side effects of Wegovy?
What are the worst side effects of Wegovy?
When do Wegovy side effects start?
How long do the side effects of Wegovy last?
Do Wegovy injection side effects differ from the Wegovy pill?
How can you avoid Wegovy side effects?
Most common Wegovy side effects and how to manage them
Less common Wegovy side effects and how to manage them
Serious Wegovy side effects and how to manage them
What are Wegovy alternatives if side effects are difficult to manage?

What are the most common side effects of Wegovy?

The most common Wegovy side effects happen in the digestive system, including (1-6):

Feeling sick (nausea)
Being sick (vomiting)
Diarrhoea
Constipation
Stomach or abdominal pain

Headaches and tiredness are also very common. These symptoms are particularly common when your Wegovy dose is increased, but usually improve as your body gets used to the medication (2-4).

All the above side effects are classed as “very common,” meaning they affect more than 1 in 10 people (2,3). But medical studies give us even more insight. In the STEP-1 trial on Wegovy 2.4mg injections, 74.2% experienced at least one digestive side effect (4). More specifically:

44.2% experienced nausea
31.5% experienced diarrhoea
24.8% experienced vomiting
23.4% experienced constipation
15.2% experienced headaches
10.0% had stomach pain (5).

A similar pattern was seen with oral Semaglutide in the OASIS 1 trial, where digestive side effects were also very common and were mostly mild to moderate (6).

Not everyone will experience these symptoms. Some people have few or no troublesome side effects on Wegovy, as everyone responds differently to medication.

What are the worst side effects of Wegovy?

What counts as the “worst” Wegovy side effect will differ from person to person.

For some people, persistent nausea, vomiting, diarrhoea or constipation can be the most difficult because they affect everyday life. Severe vomiting or diarrhoea can also cause dehydration, which may worsen kidney function, particularly if you already have kidney problems (2,3,8).

Others may be more concerned about less common side effects such as hair loss, which can be distressing, or gallstones, which can be painful and may need medical treatment (2,3,9).

There are also much rarer but serious side effects that need urgent medical attention, including:

Acute pancreatitis
A serious allergic reaction
Bowel obstruction
A rare eye condition called non-arteritic anterior ischaemic optic neuropathy (NAION) (2,3,7).

When do Wegovy side effects start?

There is no set number of hours or days after starting Wegovy you will get side effects. Some people notice symptoms very early in treatment, while others may only experience them after their Wegovy dose is increased – or not at all.

What we do know is that Wegovy side effects are particularly likely during dose escalation, meaning:

When you first start treatment
While your dose is being increased (3).

Wegovy dosage is always started low and slowly increased for this reason. Giving your body time to adjust helps reduce the likelihood of common side effects (2,3).

Serious side effects are not limited to when your dose is being increased. Symptoms such as severe, persistent abdominal pain or signs of a serious allergic reaction should always be taken seriously, even if you have been taking the same Wegovy dose for some time (2,3,7).

How long do the side effects of Wegovy last?

Most Wegovy side effects do go away or improve as your body gets used to treatment.

Nausea, vomiting and diarrhoea usually settles within days, while constipation tends to last several weeks (4,5). In the STEP-1 clinical trial of the 2.4mg Wegovy injection (5):

Nausea typically lasted around 8 days
Diarrhoea typically lasted around 3 days
Vomiting typically lasted around 2 days
Constipation typically lasted around 47 days

These figures are based on the median duration of each side effect, so some people’s symptoms last for less time and others last longer (5).

Most people find the side effects often improve by the time their next dose increase is due (4,5). But because side effects are more likely when increasing your dose, they may return temporarily when you move to a higher strength injection or tablet.

If you're still experiencing side effects when it's time to increase your dose, your prescriber may delay the increase until your symptoms have settled (2).

Do Wegovy injection side effects differ from the Wegovy pill?

Everything we’ve covered so far applies to both Wegovy injections and Wegovy tablets. Both contain the same active ingredient, Semaglutide, so share almost identical side effect profiles (2,3).

There are, however, a couple of differences when comparing the Wegovy pill vs injection (2,3):

Indigestion is more common with Wegovy tablets. It is classed as a very common side effect of the tablets, compared with common for the injection.
Injection-site reactions only happen with Wegovy injections. These are reactions such as redness or irritation in the area where you inject the medicine.

Switching from the Wegovy injection to the pill may change these two side effects, but it won’t necessarily stop side effects such as nausea, diarrhoea, vomiting or constipation. Both ways of taking Semaglutide can cause these symptoms, particularly while your dose is being increased (2-6).

If you're considering switching because of side effects, speak to your prescriber first. They can help you work out whether changing how you take Wegovy is likely to help.

How can you avoid Wegovy side effects?

There is no way to avoid Wegovy side effects completely. People respond differently to Semaglutide, and you cannot know exactly which side effects you will experience, if any, until you start treatment.

However, there are ways you can reduce your risk of side effects while taking Wegovy:

Take Wegovy exactly as prescribed. Stick to the Wegovy dose that’s right for you and do not use it more often than prescribed. Taking extra Wegovy will not make you lose weight faster and could increase your risk of side effects (2,3).
Don't rush to increase your dose. Both Wegovy injections and Wegovy pills use a gradual dosing guide. If your prescriber delays your next dose increase because you are struggling with side effects, don’t see this as a failure. The aim is to find a dose you can manage, not to reach the highest dose as quickly as possible (2,3).
Follow the instructions for your form of Wegovy. Wegovy injections are taken once weekly, while tablets are taken once daily and have specific instructions on how to take the Wegovy pill correctly. Follow the directions supplied with your treatment (2,3).
Make sure your prescriber knows your medical history and other medicines. Some health conditions and medicines can make Wegovy unsuitable or increase particular risks. For example, taking insulin or a sulfonylurea alongside Wegovy can increase the risk of low blood sugar, so your diabetes treatment may need adjusting (2,3).

Most common Wegovy side effects and how to manage them

You cannot prevent every side effect, but many of the common Wegovy side effects can be successfully managed if they do happen to you.

Sickness and nausea

If Wegovy makes you feel sick, try:

Eating smaller meals
Eating slowly and stopping when you feel full
Choosing plain, lower-fat foods such as crackers, toast or rice
Avoiding fatty, fried or spicy foods, which can make nausea worse for some people
Taking small, regular sips of fluid if you are struggling to drink normally (10)

Important: Contact your prescriber if you are repeatedly vomiting or cannot keep fluids down. Vomiting can cause dehydration, which can sometimes affect kidney function (2,3,8).

Tiredness and fatigue

Tiredness is a common side effect of taking Wegovy. If you’re feeling more tired than usual after starting Semaglutide treatment, try:

Eating regular meals, even if your appetite is low
Eating at set times if reduced appetite means you forget or skip meals
Choosing nutritious foods high in protein
Drinking enough fluids, particularly if you have vomiting or diarrhoea
Getting enough sleep and keeping a regular sleep routine

Diarrhoea

If you have diarrhoea while taking Wegovy, the main priority is replacing the fluids and salts you lose. Make sure you (8,10):

Drink water regularly throughout the day

Sip water if you feel sick to help keep fluids down

Choose drinks that contain electrolytes to replace salts lost

Avoid coffee, alcohol, dairy, or sugary drinks, which can make diarrhoea worse

Eat plain foods until your stomach settles

Important: Speak to your prescriber if diarrhoea is severe or persistent, or you develop signs of dehydration such as a very dry mouth, dizziness or needing to pee less often than usual (8,10).

Headaches

If you get a headache while taking Wegovy, try:

Drinking regularly, particularly if you have vomiting or diarrhoea
Eating regular meals, even if Wegovy has lowered your appetite
Don’t go long periods without eating because you don't feel hungry
Taking over-the-counter painkillers, if needed.
Low blood sugar can cause headaches, particularly if you have diabetes and take insulin or a sulfonylurea. If you’re diabetic, make sure to follow your usual advice for monitoring and managing low blood sugar (2,3).

Constipation

If Wegovy makes you constipated, try:

Drinking plenty of fluids
Gradually increasing the amount of fibre in your diet
Going for a brisk walk or doing another type of exercise to “wake up” your bowels
Going to the toilet when you feel the urge (11).
Ask your pharmacist about a constipation treatment (laxative) if these changes are not enough

Important: Seek urgent medical advice if you have severe constipation with significant stomach pain, bloating or vomiting, as these can be symptoms of a bowel obstruction (2,3).

Stomach or abdominal pain

Mild discomfort can occur alongside other digestive symptoms and can be managed similarly:
Eating smaller meals
Eating slowly and stopping when you feel full
Avoiding foods that seem to trigger your symptoms
Keep drinking enough fluids
Manage constipation, diarrhoea or indigestion if these are adding to your discomfort

Important: Severe stomach pain should not be managed at home. Seek medical attention if the pain does not go away, particularly if it spreads to your back, as this can be a sign of pancreatitis (2,3,7).

Less common Wegovy side effects and how to manage them

Wegovy can also cause several side effects that are reported less frequently than nausea, diarrhoea, constipation and other very common symptoms (2,3).

Bloating

Bloating is less common than other digestive side effects. If Wegovy makes you bloated, try (12):

Eating smaller meals
Eating slowly and chewing your food thoroughly
Stopping eating when you feel comfortably full
Avoiding fizzy drinks if they make your bloating worse
Keeping track of foods that seem to trigger your symptoms

Indigestion and heartburn

Heartburn from Wegovy can be managed by taking indigestion treatments like an antacid or alginate for short-term relief – your pharmacist can help you choose one that's suitable (13).

You can also help improve symptoms by:

Eating smaller meals
Eating slowly
Avoiding lying down soon after eating
Elevating your head when sleeping if you still have indigestion at night
Cutting down on foods or drinks that you notice trigger your symptoms (13)

Dizziness

If Wegovy makes you feel dizzy, try sitting or lying down until the feeling passes. Do not drive or use machinery while you feel dizzy on Wegovy (2,3).

You can reduce the chance of feeling dizzy by:

Getting up slowly from sitting or lying down
Drinking regularly throughout the day, especially if you are vomiting or have diarrhoea
Eating regularly, even if you don’t have much of an appetite

Excessive gas and burping

Gas (flatulence) and burping can be managed by:
Eating slowly to help reduce how much air you swallow with food
Chewing your food thoroughly with your mouth closed
Gently massaging the stomach to help release trapped air
Avoiding fizzy drinks, which add extra air into your gut
Cutting back on foods high in sulphur like cabbage and beans (12)

You may also want to ask your pharmacist about simeticone, an over-the-counter medicine that can help relieve trapped wind and bloating (12).

Changes in skin sensation

Wegovy can sometimes cause altered skin sensations (dysaesthesia), such as unusually sensitive skin, tingling, burning sensations or pain from something that would not normally hurt (2,3).

If this happens, try:

Keeping track of where and when the sensation occurs
Wearing loose clothing if your skin feels sensitive to touch
Avoiding skincare products or other things that irritate the affected area
Monitoring whether the sensation improves over time

Dysaesthesia generally tends to be mild to moderate and most people recover while continuing Wegovy (2,3). Speak to your prescriber if the sensation is painful or difficult to manage.

Gallstones

Gallstones do not always cause symptoms, so you may not know you have them. If they do cause problems, pain is usually the main thing to look out for (9).

Treatment depends on how troublesome they are and may include:

Pain relief for symptoms, or
Surgery to remove the gallbladder if gallstones are causing repeated or serious problems (9).

Speak to a healthcare professional if you develop persistent or recurring pain in the upper part of your stomach, particularly on the right-hand side.

Important: Get urgent medical advice if the pain is severe or you also have vomiting, a temperature or yellowing of your skin or the whites of your eyes. These can be signs of a complication (9).

Hair loss

Hair loss with Wegovy may be linked to substantial weight loss, as it was reported more frequently in trials by people who lost at least 20% of their weight (2).

There is no specific treatment for Wegovy-related hair loss. If you notice increased hair shedding, try:

Eating a balanced diet even though your appetite is lower
Making sure you're getting enough protein, iron and other essential nutrients
Avoiding very restrictive diets or losing weight faster than advised
Treating your hair gently and avoiding tight hairstyles or excessive heat while it is shedding

Speak to your GP if hair loss is significant, continues for several months or you notice other changes such as bald patches or scalp problems. They can check for other possible causes, including nutritional deficiencies.

Serious Wegovy side effects and how to manage them

Serious side effects of Wegovy are much less common, but they need medical attention rather than trying to manage them yourself at home (2,3,7).

Pancreatitis

Pancreatitis is inflammation of the pancreas and can become serious if it is not treated. The MHRA strengthened its warnings about pancreatitis with GLP-1 medicines in January 2026 following rare reports of severe and fatal cases (7).

Look out for severe, persistent stomach pain that does not go away, particularly if it spreads to your back. You may also feel or be sick (2,3,7).

What to do: Stop taking Wegovy and seek urgent medical attention if you think you may have pancreatitis. If pancreatitis is confirmed, Wegovy should not be restarted (2,3,7).

Kidney problems and dehydration

Severe or ongoing vomiting and diarrhoea can cause dehydration, which may worsen kidney function,especially if you already have kidney problems (2,3).

Look out for signs of significant dehydration, such as:

Peeing much less than usual
Feeling very thirsty or having a very dry mouth
Persistent dizziness or weakness
Being unable to keep fluids down (8)

What to do: Contact a healthcare professional if you develop signs of dehydration. You may need treatment to replace fluids and salts and, in some cases, kidney function may need checking (2,3,8).

Serious allergic reactions

Rarely, Wegovy can cause a serious allergic reaction (2,3). Look out for:

Difficulty breathing or swallowing
Swelling of your face, lips, tongue or throat
Feeling very dizzy or faint

What to do: Get emergency medical help immediately if you develop signs of a serious allergic reaction (2,3). Do not wait to see if these signs improve by themselves.

Bowel obstruction

A bowel obstruction is a blockage that prevents waste from moving normally through your bowel. It has been reported in people taking Wegovy, although it is not known how often it occurs (2,3).

Look out for:

Severe constipation
Significant or worsening stomach pain
A swollen or bloated stomach
Vomiting

What to do: Seek urgent medical attention if you develop symptoms that could indicate a bowel obstruction. Do not continue treating severe constipation at home if you have other signs.

Serious eye problems

Wegovy has been linked to a very rare eye condition called non-arteritic anterior ischaemic optic neuropathy (NAION), which can cause sudden loss of vision (2,3).

If you have type 2 diabetes, Wegovy can also worsen diabetic retinopathy in some people. Tell your prescriber if you notice new or worsening changes to your vision.

What to do: Get urgent medical attention if you lose some or all of your vision while taking Wegovy.

Low blood sugar

Low blood sugar is particularly relevant if you have diabetes and take insulin or a sulfonylurea alongside Wegovy (2,3). Symptoms can include:

Sweating or shaking
Feeling hungry, weak or dizzy
A fast heartbeat
Difficulty concentrating or feeling confused

What to do: Follow the advice you have been given for treating low blood sugar. If you are having repeated episodes, contact your diabetes team or prescriber.

What are Wegovy alternatives if side effects are difficult to manage?

Bad Wegovy side effects do not necessarily mean treatment needs to stop. Sometimes, staying on the same dose for longer or treating the side effect can make treatment more manageable.

When side effects continue to cause problems, switching to a different treatment may be an option. Different medicines have different side-effect profiles, so experiencing side effects with Wegovy does not automatically mean you will have the same experience with another treatment.

Below are some alternatives you may wish to consider:

Mounjaro – If you still want a weekly injection, Mounjaro is another option. It contains Tirzepatide rather than Semaglutide. Digestive problems are still among the most common Mounjaro side effects, but there is a difference in side effects between GLP-1 treatments (14).
Foundayo – If you would prefer a daily tablet for weight loss, Foundayo is similar to the Wegovy Pill but contains a different GLP-1 medicine called Orforglipron. Digestive side effects are also common, but it does not contain Semaglutide (15).
Orlistat – Orlistat works differently from Wegovy by reducing how much fat your body absorbs from food, so its side effects are different too. Oily stools, wind and needing to open your bowels urgently are among the most common (16).
Mysimba – Mysimba for weight loss works on areas of the brain involved in appetite and reward rather than acting like a GLP-1 medicine. It has a different side-effect profile, although nausea, constipation, vomiting and headaches can still happen (17).

Do not stop Wegovy or switch weight loss medicines without speaking to your prescriber first. The most suitable alternative depends on the side effects causing problems, medical history, other medicines and your goals from treatment, which your prescriber can help you figure out.

If you are considering changing treatment, contact our team. We can help you weigh up the side effects you are experiencing against the benefits from Wegovy and discuss suitable alternatives.