Wegovy^® Side Effects U.K.: What to Expect

Reviewed by Claudia Berty, MBChB MRCGP DFSRH PGDipENT

Written by Our Editorial Team

Key Takeaways:

• Common Wegovy® side effects include nausea, diarrhoea, vomiting, and constipation. These usually ease over time.

• Serious but uncommon effects can include gallstones, pancreatitis, and diabetic eye complications.

• Most common side effects can be managed at home by eating small meals, staying hydrated, and taking OTC medicines.

• Speak with your GP if you’re experiencing persistent or severe side effects.

Wegovy® (semaglutide) can be an effective medication for weight management — and like all medicines, it can come with side effects.

The most common Wegovy® side effects are gastrointestinal. Nausea, diarrhoea, vomiting, constipation, stomach pain, bloating, and heartburn are all common, particularly when you start taking the medication or increase your dose.

We’ll cover the possible side effects of Wegovy®, when they tend to appear, how long they may last, and practical ways to feel better.

What Is Wegovy®?

Wegovy® is a once-weekly injection that contains semaglutide, a glucagon-like peptide-1 (GLP-1) receptor agonist.

Semaglutide acts on GLP-1 receptors in the brain, which are responsible for regulating appetite. The medicine helps by:

• Reducing hunger

• Increasing feelings of fullness (satiety)

• Slowing how quickly food moves through the gut (delayed gastric emptying)

• Regulating blood sugar (glucose) levels

In the United Kingdom, the Medicines and Healthcare products Regulatory Agency (MHRA) approved Wegovy® for treating obesity in adults. It’s also approved for preventing weight-related cardiovascular disease.

Semaglutide is also available under the brand name Ozempic®. But in the U.K., Ozempic® isn’t licensed as a weight loss medicine — only as a treatment for type 2 diabetes. Both Wegovy® and Ozempic® are manufactured by Novo Nordisk.

While Wegovy® is considered effective and safe for most people, it does have potential side effects and risks. Generally, higher doses are associated with an increased risk of side effects.

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Common Wegovy® Side Effects

The most common side effects of Wegovy® — that is, the side effects that may affect more than one in 10 people — include:

• Nausea

• Vomiting

• Diarrhoea

• Constipation

• Abdominal pain

• Headache

• Weakness

• Tiredness

Other common side effects, affecting up to one in 10 people, include:

• Feeling dizzy or lightheaded

• Indigestion (dyspepsia)

• Burping and flatulence

• Bloating

• Acid reflux or heartburn

• Hair loss (especially if you’re losing weight rapidly)

• Injection site reactions (like itching, redness, or irritation)

Most of these side effects are mild to moderate, and they tend to settle over time. Common side effects can often be managed with over-the-counter (OTC) medications and lifestyle adjustments, like eating smaller meals and getting enough water.

There are relatively common side effects that are more serious and require medical attention. These side effects, which also affect up to one in 10 people, include:

• Low blood sugar (hypoglycaemia) in patients with diabetes

• Gallstones

• Inflamed stomach (gastritis)

• Complications of diabetic eye disease (diabetic retinopathy)

If you have the symptoms of these side effects, it’s imperative that you go to hospital for emergency medical care.

Less Common Side Effects of Wegovy®

These side effects are less common — affecting up to one in 100 people — but they’re generally more serious:

• Fast heartbeat (tachycardia)

• Low blood sugar in patients without diabetes

• Increased levels of bilirubin and pancreatic enzymes in the blood

• Inflammation of the pancreas (acute pancreatitis)

• Bladder stones or other kidney problems

Another very rare side effect is a severe allergic reaction. Seek immediate medical help if you have the symptoms of anaphylactic shock, including:

• Breathing problems

• Swelling of the face, lips, tongue, or throat

• Difficulty swallowing

• Wheezing

• Fast heartbeat

• Pale and cold skin

• Feeling dizzy or weak

If you experience any side effects of Wegovy®, report them to the MHRA’s Yellow Card Scheme. This helps the MHRA identify safety issues with medications.

Wegovy® Side Effect Cheat Sheet

Many of the common side effects of Wegovy® can be managed with over-the-counter meds, changes to your diet, and small lifestyle tweaks.

Here’s a simple cheat sheet for coping with these side effects.

Wegovy® and Muscle Loss

Another potential long-term side effect of Wegovy® is muscle loss. Muscle loss is always a potential risk of quick weight loss, as your body may burn lean muscle for energy.

Muscle loss is bad news for your weight loss efforts and your overall health. It can:

• Affect your metabolism

• Lead to decreased strength

• Make it harder to do everyday tasks — like walking, opening jars, or moving furniture

To avoid muscle loss on Wegovy®:

• Eat a healthy, balanced diet. Wegovy® dampens your appetite, so you need to put in extra effort to ensure you’re getting enough nutrients. Try not to skip meals too often.

• Get enough protein. Research suggests weight‑loss seekers eat 1.2 to 1.6 grams (g) of protein per kilogram (kg) of bodyweight — up to 2.0 g/kg if you’re training hard.

• Engage in regular strength training. For example, lift weights, do bodyweight exercises, or use resistance bands. Aim to do at least two sessions a week.

If you’re concerned about muscle loss, speak with your general practitioner (GP) or private healthcare professional.

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Wegovy® Drug Interactions

Wegovy® can affect how other medications impact your body, and vice versa. Sometimes, certain drug combinations can increase your risk of side effects.

As such, Wegovy® shouldn’t be used with:

• Other GLP-1s, like Mounjaro® (tirzepatide) and Victoza® (liraglutide)

• Other diabetes drugs, like sulfonylureas and insulin, without a GP’s approval

Since Wegovy® delays gastric emptying, it may affect how oral medications are absorbed. For this reason, it’s essential to tell your GP or prescribing clinician about all the medications you use, from prescription pills to OTC drugs and supplements.

It’s not yet clear whether Wegovy® affects oral contraception. If you’re on oral contraception, it’s a good idea to use another form of contraception to be on the safe side — for example, condoms.

If you use any OTC or prescription medicines, ask your GP or prescribing healthcare provider about pregnancy risk and contraception options.

Who Shouldn’t Use Wegovy®

Some people are at particular risk for developing Wegovy® side effects. For this reason, it’s usually recommended that you avoid Wegovy® if you have a history of:

• Pancreatitis

• Gallbladder disease

• Kidney problems

• Diabetic retinopathy

• Eating disorders

• Allergic reactions to semaglutide

You should also avoid Wegovy® if you:

• Are pregnant, breastfeeding, or trying to conceive. It’s not clear whether Wegovy® is safe during pregnancy and breastfeeding, so it’s recommended that you avoid it if you’re pregnant or nursing.

• Have a personal or family history of medullary thyroid carcinoma (MTC) or multiple endocrine neoplasia (MEN 2). In some studies, mice on GLP-1s developed thyroid tumours. Although these findings haven’t been replicated in human studies, it’s best to avoid Wegovy® if you have a personal or family history of thyroid cancers.

If you’re unsure if Wegovy® is safe for you, speak with your prescribing clinician. They may be able to recommend a different weight loss approach that’s safer for you.

Alcohol and Wegovy®

Can you drink alcohol on Wegovy?® Yes, generally.

There’s no specific listed interaction with alcohol, but drinking can worsen gastrointestinal symptoms (like nausea and upset stomach). Drinking may affect blood sugar, especially if you’re eating less than usual.

Many alcoholic drinks can also be high in calories, which can slow down your weight loss efforts.

If you choose to drink, go slowly, avoid drinks that may trigger side effects, and prioritise hydration and food. Ask your GP or private prescriber if alcohol is suitable for you.

Wegovy® U.K. Side Effects: In Summary

Wegovy® is an effective weight loss treatment for many people, but as with all medications, it can have unpleasant side effects. Fortunately, most Wegovy® side effects are temporary and manageable.

Here’s the long and short of it:

• The most common side effects of Wegovy® include nausea, vomiting, constipation, headaches, tiredness, and injection site reactions. These can usually be managed at home or with OTC medications.

• More serious side effects include kidney problems, pancreatitis, low blood sugar, and gallstones. Seek immediate medical help if you think you’re experiencing one of these side effects.

• Small adjustments can help you cope with the milder side effects. Eating a healthy diet, drinking plenty of water, resting, and over-the-counter medication may help.

Keep your GP or private healthcare professional informed about your side effects, report them to the Yellow Card Scheme, and reach out for help if needed. If you have any red-flag symptoms, go to your nearest A&E.

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FAQs

See answers to common questions about Wegovy® side effects.

What are the most common side effects of Wegovy®?

The common side effects of Wegovy are mostly gastrointestinal symptoms, like nausea, vomiting, diarrhoea, constipation, stomach pain, headache, and tiredness. These symptoms are usually mild to moderate and tend to improve as your dose is titrated.

When do side effects of Wegovy® start?

In clinical trials, side effects most often appeared in the first few weeks after starting Wegovy® or after a dose increase. For many people, symptoms ease once the body adapts and the dose stabilises. That’s one reason the dosing schedule steps up gradually.

Can Wegovy® cause constipation — and how do I manage it?

Yes, Wegovy® can cause constipation. It’s a common side effect of GLP-1s. Hydration, eating foods with fibre, movement, and (if advised) a stool softener or fibre supplement can help. Let your prescriber know if symptoms persist.

Is Wegovy® available on the NHS?

Yes, Wegovy® is available on the NHS for eligible adults via specialist weight-management services. However, availability is very limited, and waiting lists are long — most people don’t end up being able to access it.

To qualify, you need to have at least one weight-related health condition, as well as a body mass index (BMI) of at least 35 or a BMI of 30 to 34.9 and meet the National Institute for Health Care and Excellence (NICE) criteria for referral to specialist overweight and obesity management services. If you’d rather skip the queues, Wegovy® is also available through regulated private telehealth platforms, like Hers U.K.

Are there serious risks of Wegovy® I should know about?

Rare but serious risks of Wegovy® include pancreatitis, gallbladder problems, severe allergic reactions, and diabetic retinopathy complications (in people with diabetes). Seek care promptly if warning symptoms appear.

Does Wegovy® interact with other medicines?

Wegovy® can delay stomach emptying, which may affect how some medicines are absorbed. Always share a full meds list (including OTC medicines and supplements) with your GP or private healthcare professional before taking Wegovy®. See the patient leaflet, and ask your clinician for personalised advice.

This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for and should never be relied upon for professional medical advice. Always talk to your GP about the risks and benefits of any treatment.