Comprehensive Guide To Understanding Wegovy Side Effects

Whether you’ve just started taking Wegovy or you’re considering starting weight loss treatment, it’s important to understand side effects and how to manage them. Here, our clinical team has put together a comprehensive guide to some of the known side effects of both oral and injectable Wegovy, and what to do if you experience them.

Article summary:

• Wegovy is a GLP-1 medication that works by mimicking a gut hormone involved in digestion to increase feelings of fullness.
• Wegovy contains semaglutide as an active ingredient, and because it works on your digestive system, the most common side effects are stomach-related symptoms, such as nausea, diarrhoea and constipation.
• Like all medicines, Wegovy can cause side effects and they can be mild to moderate. Side effects most likely occur when you first start treatment or move up a dose.

Wegovy side effects summary

Starting a new medication can bring up a lot of questions, and it's completely natural to wonder how your body might respond. If you've been prescribed Wegovy, or you're thinking about it, you might have heard about side effects like nausea or constipation and feel unsure about what to expect.

The good news is that for many people, side effects are mild, tend to be most noticeable in the first few weeks or after a dose increase, and often ease as your body adjusts.

In this guide, we'll take you through the most common side effects, what you can do to manage them, and when it's important to seek medical attention, so you can feel informed and supported every step of the way.

Wegovy Pill side effects

Wegovy (the tablet and the injection) contain the exact same active ingredient: semaglutide. As a result, side effects of both are very similar. The most common side effects when taking oral semaglutide are very similar to the Wegovy pen, and include nausea, vomiting, diarrhoea, constipation, abdominal pain and indigestion.

The injection and oral Wegovy tablet have different dosing schedules: the injection is taken weekly and the tablet is taken daily. Although they share similar ingredients, these treatments could result in different side effects.

Is Wegovy safe?

Wegovy is considered safe and effective for people who meet the prescribing criteria and have been assessed as suitable by a healthcare professional. Before prescribing, your clinician will review your medical history, any medication you’re currently taking and your body mass index (BMI).

Wegovy should not be taken during pregnancy or while breastfeeding. If you're planning to become pregnant, you should stop taking Wegovy at least 2 months beforehand.

What are the serious side effects of taking Wegovy?

Serious side effects are uncommon, but it's important to know what to look out for. Serious side effects include:

• Acute pancreatitis (inflammation of the pancreas)
• Gallbladder problems, including gallstones and an inflamed gallbladder
• Severe allergic reaction (anaphylaxis)

We explain the warning signs of each below.

There are some other risks to be aware of, including:

• Dehydration: Losing fluids through vomiting or diarrhoea can, in some cases, affect your kidneys. Keep sipping fluids and seek medical attention if you can't keep them down.
• Low blood sugar: This is more likely if you also take medications for diabetes, such as insulin or sulfonylureas.

Common Wegovy side effects

The most common side effects associated with Wegovy (semaglutide) affect your digestive system. The good news is there are simple things you can do to feel more comfortable.

Short term side effects

Nausea (feeling sick)

What is it?

Nausea is a queasy, unsettled feeling that can make you feel like you might be sick. You may also notice a smaller appetite, bloating or stomach discomfort.

How long does it last?

Nausea is most common when you first start taking Wegovy or after a dose increase. It usually improves as your body adjusts, but how long this takes varies from person to person. Please contact us if your nausea is severe, doesn’t improve or makes it hard to eat and drink. [1]

Why does this happen?

Wegovy slows how quickly food leaves your stomach, so you stay fuller for longer. This stretches the stomach and sends signals to your brain that can trigger the sensation.

Here’s what we recommend to manage nausea:

• Drink plenty of fluids (cold water, herbal teas)
• Get lots of fresh air
• Eat small and frequent meals
• Reduce intake of foods high in sugar and fat
• Avoid cooking or eating spicy or strong smelling foods

Constipation

What is it?

Constipation means pooing less often than usual, or passing poo that’s hard, dry or difficult to pass. You may also experience bloating, stomach discomfort or a feeling that your bowel has not fully emptied.

How long does it last?

Constipation may occur when you start treatment or increase your dose. It may improve as your body adjusts, but contact us or your pharmacist if it's ongoing, painful or you haven't been for several days.

Why does this happen?

Wegovy slows digestion. Eating and drinking less overall may also make poo harder to pass.

Here's what we recommend to manage constipation:

• Drink plenty of fluids (water, herbal teas), aiming for around 6-8 glasses a day
• Gradually add more high-fibre foods to your diet, such as prunes, figs, and oats
• Take regular walks, as gentle movement can stimulate bowel movements
• Ask a pharmacist about a suitable laxative if lifestyle changes aren’t enough. At MedExpress we offer Psyllium Husk as an option.

Contact your GP if:

• Your constipation does not improve even after following the advice above
• You notice blood in your stool

Indigestion

What is it?

Indigestion is discomfort in the upper abdomen. It can cause heartburn, bloating, burping, nausea or a sour taste in your mouth. You may notice symptoms are worse after eating or when lying down.

Why does this happen?

Because food stays in your stomach for longer, stomach acid is more likely to rise into your food pipe (acid reflux). This can cause a burning feeling in your chest or throat.

How long does it last?

Indigestion is often temporary, particularly after starting Wegovy or increasing your dose. It may come back after certain meals. Contact us if it's frequent, severe or not improving.

Here's what we recommend to manage indigestion:

• Reducing your caffeine intake
• Don’t eat right before you go to bed
• Avoid rich, spicy, or fatty foods
• Try heartburn medication if necessary

Diarrhoea

What is it?

Diarrhoea means passing loose or watery poo more often than usual. You may also have stomach cramps, bloating or a sudden need to go to the toilet.

Why does this happen?

Wegovy changes how food moves through your gut, which may affect how well your bowel absorbs water.

How long does it last?

Diarrhoea often settles within a few days, but it can last longer or return after a dose increase. Contact us if it’s severe or lasts more than a few days.

Here's what we recommend to manage diarrhoea:

• Drink plenty of fluids (water, herbal teas)
• Eat small and frequent meals
• Prioritise rest and recovery
• Consider taking oral rehydration salts from a pharmacist to replace lost fluids and electrolytes
• Paracetamol for pain relief

Contact your GP or call 111 if:

• You have been vomiting for more than a couple of days.
• You have signs of dehydration, such as dark urine or urinating less than usual.
• You take oral contraception and have vomited within 3 hours of taking your contraceptive pill. You may need to take another dose to help prevent an unwanted pregnancy.

Important: Call 999 or go to A&E if:

• Your vomit contains something that looks like coffee granules.
• Your vomit contains blood.
• You have a fever alongside your vomiting.
• You have sudden or severe stomach pain alongside your vomiting.
• You are vomiting three or more times a day.

Vomiting

What is it?

Vomiting, or being sick, is the forceful emptying of the stomach through the mouth. It may be accompanied by nausea, stomach discomfort, bloating or a feeling of fullness.

Why does this happen?

Wegovy slows stomach emptying to help you feel fuller for longer. However, because food stays in the stomach longer and causes it to stretch, it can trigger signals to the brain that may lead to vomiting.

How long does it last?

Vomiting is often short-lived, but it can recur after starting treatment or increasing the dose. If you cannot keep fluids down, contact your prescriber promptly because vomiting can lead to dehydration.

Here's what we recommend to manage vomiting:

• Stay hydrated with water, or herbal teas like ginger or peppermint
• Eat small and frequent meals to keep your energy levels up

Contact your GP or call 111 if:

• You have been vomiting for more than a couple of days.
• You have signs of dehydration, such as dark urine or urinating less than usual.
• You take oral contraception and have vomited within 3 hours of taking your contraceptive pill. You may need to take another dose to help prevent an unwanted pregnancy.

Important: Call 999 or go to A&E if:

• Your vomit contains something that looks like coffee granules.
• Your vomit contains blood.
• You have a fever alongside your vomiting.
• You have sudden or severe stomach pain alongside your vomiting.
• You are vomiting three or more times a day.

Serious side effects

Serious side effects of Wegovy are uncommon or rare, but it’s important that you know what to look out for. If you notice any of the symptoms below, don't take your next dose, and get medical help as described in each section.

Pancreatitis

What is it?

Acute pancreatitis is a serious condition where your pancreas suddenly becomes swollen and painful (inflamed). It needs urgent treatment in hospital. [2]

The main symptom of acute pancreatitis is pain in your tummy (abdomen). You may also have a high temperature and feel sick or be sick (nausea and vomiting).

Tummy pain may:

• Come on suddenly and not go away
• Feel severe, sharp or knife-like
• Affect the upper tummy, between the ribs, one side or the entire tummy
• Spread to your sides and back
• Get worse after eating, moving around or lying down.

Severe, persistent stomach pain means:

• It’s so intense (around 8 or more out of 10) that you can’t focus on anything else
• It makes it nearly impossible to handle normal daily tasks (like walking, getting dressed, or eating)
• It doesn’t improve with over-the-counter pain relief or rest
• It radiates to your back or underneath your right ribcage or your right shoulder
• You also have severe vomiting (3 or more times a day, or having blood or something that looks like coffee grounds in vomit)

If you notice any of these symptoms, call 999 or head to A&E right away.

Why does this happen?

It's not fully understood why Wegovy causes acute pancreatitis. It may involve direct effects on the pancreas, or gallstones, which can occur with treatment and rapid weight loss.

How long does it last?

Acute pancreatitis is usually diagnosed using blood tests and sometimes a CT scan. It's a serious condition that needs treatment in the hospital straight away.

You'll be monitored to see how serious your condition is and if it's causing any other problems, such as an infection.

Most people with acute pancreatitis start to get better within a week and can leave hospital in 5 to 10 days. If you have severe pancreatitis or it's causing other problems, you may need to stay in hospital for longer. [3]

Gallstones

What is it?

Gallstones can occur during weight loss treatment, particularly with rapid weight loss. This is a common side effect while taking Wegovy, affecting approximately 1 in 10 people.

Why does this happen?

Rapid or significant weight loss can increase the risk of gallstones. Inflammation of the gallbladder usually happens when a gallstone blocks to the cystic duct. [4]

Here’s what we recommend to manage gallbladder problems:

If you develop symptoms of gallstones, such as severe or constant stomach pain, seek medical attention promptly. The stomach pain can:

• Feel severe, constant and last longer than 30 minutes.
• Spread from the middle of your stomach to under your right ribcage.
• Make you feel sick or vomit.

See a GP as soon as possible if you develop sudden and severe abdominal pain, particularly if it lasts longer than a few hours or is accompanied by other symptoms, such as jaundice and a high temperature.

Anaphylaxis or a severe allergic reaction

Anaphylaxis is a rare but life-threatening allergic reaction that happens very quickly. Call 999 if you think you or someone else is having an anaphylactic reaction. Signs can include:

• Difficulty breathing, fast breathing or wheezing
• Tightness in the throat, or trouble swallowing
• Feeling faint, dizzy or confused, or collapsing
• Swelling of the lips, mouth, tongue, or throat

These symptoms may be accompanied by vomiting, or a rapid heartbeat.

Understanding side effects

Why side effects change from week to week

It's normal for side effects to vary from week to week. Your body may still be adjusting to treatment, and your dose may be increasing. Everyday things like what you eat, alcohol, illness, how much you drink and stress can also affect how you feel.

How do I know whether it’s the GLP-1 medication causing the side effect?

It can be difficult to tell from symptoms alone. A side effect may be more likely to be linked to Wegovy if it began soon after starting treatment, appeared after a dose increase, or is a recognised side effect such as nausea, vomiting, diarrhoea, constipation, abdominal pain or indigestion.

Wegovy side effect FAQs

Are Wegovy side effects affected by alcohol?

Some people find that alcohol can worsen side effects including nausea and vomiting, particularly in the early weeks of treatment or during dose increases. It's worth paying attention to how your body responds, and if you notice side effects are worse after drinking alcohol, cutting back may help. [5]

Do Wegovy injection and Wegovy Pill side effects differ?

Both forms of Wegovy contain semaglutide and can cause similar side effects, specifically nausea, vomiting, diarrhoea, constipation and other symptoms including headaches and fatigue.

Are there different side effects in women and men?

No. Current evidence from clinical trials suggests that the known side effects of Wegovy, and how often they happen, apply to all adults. [6]

Do side effects change depending on dose strength?

Yes, Wegovy side effects can change as you adjust your dose. Digestive symptoms like nausea, diarrhoea or indigestion for example could temporarily feel more intense when you first move up, until your body gets used to a higher dose. That’s why Wegovy is started at a low dose and increased gradually. If you’re struggling with side effects after a dose increase, you could consider remaining at your current dose for longer.

Medication timing and routines

Wegovy is administered once a week, and staying consistent with your injection routine helps your body adjust and prevent side effects. [7]

There's no single best day to inject. The most important thing is to pick a day that fits your life and routine. These ideas may help:

Friday or Saturday: Gives you time to manage any side effects (like nausea or fatigue) over the weekend, without the pressure of a workday.

Thursday: If you tend to eat more at weekends, injecting towards the end of the week may help you feel fuller and more in control of your appetite. Injecting towards the end of the week may also help reduce cravings and encourage more mindful eating.

Sunday or Monday: Can help you start the week feeling organised and set up healthy habits for the days ahead.

For the Wegovy tablet, you should:

Take one pill every morning on an empty stomach with a small sip of plain water. Then, wait 30 minutes before eating, drinking or taking any other medications.

What to do if you miss a dose

If you miss a dose of injectable Wegovy, it should be administered as soon as possible and within 5 days after the missed dose. If more than 5 days have passed, the missed dose should be skipped, and the next dose should be administered on the regularly scheduled day.

If you miss a dose of Wegovy Pill, skip that day and take the next tablet on the following day as normal. Do not take 2 tablets in 1 day.

If you have any questions about how to proceed after missing a dose, contact our clinical team for advice.

A note from our experts

“Your goals might be a priority, but it’s important to listen to your body as it adapts to the medication. Wegovy can be an effective treatment for those who are eligible , but like any medicine, it can cause side effects. The most common are digestive symptoms such as nausea, constipation, diarrhoea, vomiting and indigestion, particularly when treatment begins or the dose increases. These effects often improve as your body adjusts, and starting treatment gradually can help with tolerability.”

- Sophie Dix, Head of Medical Affairs

Ready to start your weight loss journey?

At MedExpress, we offer online consultations with regular clinical check-ins, and a range of weight loss treatments including Mounjaro, Wegovy Pen, Wegovy Pill and Foundayo and our team can help you find the right treatment for you.

References

1. Wilding JPH, Batterham RL, Calanna S. Once-Weekly Semaglutide in Adults with Overweight or Obesity. The New England Journal of Medicine [Internet]. 2021 Feb 10;384(11):989–1002. Available from: https://www.nejm.org/doi/full/10.1056/NEJMoa2032183
2. NHS. Acute pancreatitis [Internet]. nhs.uk. 2022 [cited 2026 Sept 21]. Available from: https://www.nhs.uk/conditions/acute-pancreatitis/
3. NHS. Acute pancreatitis [Internet]. nhs.uk. 2022 [cited 2026 Oct 1]. Available from: https://www.nhs.uk/conditions/acute-pancreatitis/
4. Ramírez-Mejía MM, Ponciano-Rodriguez G, Eslam M, Méndez-Sánchez N. GLP-1 receptor agonists and gallbladder disease risk: insights into molecular mechanisms and clinical implications. Therapeutic Advances in Endocrinology and Metabolism [Internet]. 2025 Dec [cited 2026 Sept 22];16. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC12739101/
5. NHS website. Semaglutide [Internet]. nhs.uk. 2026. Available from: https://www.nhs.uk/medicines/semaglutide/
6. Committee for Medicinal Products for Human Use (CHMP) Assessment report Wegovy [Internet]. 2021 [cited 2026 Sept 23]. Available from: https://www.ema.europa.eu/en/documents/assessment-report/wegovy-epar-public-assessment-report_en.pdf
7. Wegovy 0.25 mg, FlexTouch solution for injection in pre-filled pen - Summary of Product Characteristics (SmPC) - (emc) [Internet]. www.medicines.org.uk. Available from: https://www.medicines.org.uk/emc/product/13799/smpc#gref