Wegovy Side Effects: Common, Serious, and Long-Term Risks Explained

Wegovy, like any other medication, will cause side effects. It happens because the medicine changes your appetite and slows your digestive process. Most people experience symptoms like nausea, diarrhoea, constipation, and stomach pain. These are often mild and settle after a few weeks as your body adjusts.

Other people may experience severe side effects from Wegovy use that require immediate medical attention. There's also the question of the long-term side effects of this weight-loss injection, since it officially became available on the NHS and in the private market only recently, in 2023.

This guide explains everything you need to know about the side effects of Wegovy, including what’s common and which symptoms require medical attention.

What Is Wegovy and Why Does It Cause Side Effects?

Wegovy is a weekly weight loss injection containing the active ingredient semaglutide. This ingredient mimics a natural hormone called GLP-1, which helps control appetite, blood sugar, and how quickly food leaves your stomach.

UK patients must use Wegovy injection with a healthy diet and physical activity for weight management. Like other GLP-1 weight-loss injections, Wegovy helps you feel fuller for longer. You will eat less, which will help you lose weight.

According to recent results from the STEP UP trial, people taking the 7.2 mg dose of Wegovy lost 20.7% of their total body weight.

Why Do Side Effects Happen?

Wegovy side effects happen because your digestive system has to adjust. Food stays in your stomach longer, so when you eat a standard-sized, heavy, or fatty meal, you may feel overly full, which can lead to mild nausea, constipation, diarrhoea, an upset stomach, and other gastrointestinal symptoms.

Side effects may be more noticeable when you move to a higher dose. This doesn’t always mean Wegovy treatment is wrong for you. Instead, your body could need more time to adjust to the medication.

According to clinical trials published in the New England Journal of Medicine, nausea and diarrhoea were found to be among the most common side effects of Wegovy.

It's important to note that everyone responds differently to Wegovy. Your symptoms may be more severe or milder than someone else's.

The Most Common Wegovy Side Effects

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Most Wegovy side effects affect the stomach and gut. These common symptoms are usually easier to manage when you know what is causing them.

Nausea

Nausea may happen because food stays in your stomach for longer. This can stretch the stomach wall and send strong signals of nausea directly to your brain. You may feel worse after eating spicy or fatty foods because they naturally slow stomach emptying. It also happens when you eat large meals.

Quick Remedies

• Eat small, frequent meals.
• Stop eating before you're full.
• Eat bland foods such as plain biscuits.
• Sip peppermint tea.
• Drink plenty of fluids slowly.
• Get some fresh air.
• Avoid fatty or spicy foods.

Vomiting and Diarrhoea

Vomiting is the result of food staying in your stomach for too long. When you eat large meals or foods high in fat, your stomach stretches and sends an overload signal to the brain, triggering vomiting.

When food moves out of your stomach at a slower pace, the small intestine may sometimes receive a clump of poorly digested food. The intestines rapidly draw extra water from your bloodstream into the bowel to break down the stool, but this often leads to diarrhoea.

Vomiting and diarrhoea can lead to dehydration. Also, because Wegovy suppresses your appetite and thirst drives, you're less likely to drink water. This state of dehydration can cause serious complications such as kidney injury.

Quick Remedies

• Drink enough fluids throughout the day.
• Take tiny, frequent sips to avoid triggering vomiting.
• Use an oral rehydration solution (such as Dioralyte) from your local pharmacist.
• Watch out for warning symptoms such as feeling dizzy, dark urine, vomiting every time you take a sip of water, and passing very little urine.
• Speak to a doctor straight away if you notice any warning signs or severe stomach pain.

Constipation and Bloating

Constipation can happen because Wegovy slows digestion. Because waste is moving through your large intestine at a slower pace, the colon has more time to absorb water. The longer the waste sits there, the drier it becomes, making it more difficult to pass.

When you're constipated, food and gas from higher up in the digestive tract get trapped, leading to bloating. Also, as food stays in your stomach for longer, it starts to ferment, producing extra gas and causing a bloated feeling.

Quick Remedies

• Increase fibre intake gradually to give your gut time to adjust.
• Drink plenty of water and herbal teas.
• Eat less food.
• Avoid chewing gum.
• Do gentle exercises, such as a 20-minute walk, to stimulate the muscles in your intestines.

Headaches, Tiredness, and Dizziness

Headaches and fatigue can happen when you’re eating less, are dehydrated, or adjusting to lower blood sugar levels.

Because you're eating less, the sudden energy deficiency affects your brain and body, causing brain fog and tension headaches.

Also, Wegovy prevents blood sugar spikes, which can cause mild lightheadedness as your brain adapts. Note that low blood sugar is more likely if you take Wegovy with diabetes medicines such as insulin or sulphonylureas.

Quick Remedies

• Drink water throughout the day.
• Sip an electrolyte drink when you feel dizzy or get a headache.
• Eat protein first to keep energy levels stable.
• Speak to your prescriber before taking Wegovy if you use other medications for diabetes.

Less Common But Mild Symptoms

• Burping: Fermentation of food in the stomach produces gas, causing you to burp. You can manage it by avoiding heavy proteins right before bed and sipping peppermint tea to break up gas bubbles.
• Acid Reflux: Your stomach produces acid for a longer duration to try to break down food. This acid can climb up into your throat, causing reflux. Avoid eating within two to three hours of lying down. Also, you can use over-the-counter antacids to manage the symptoms.
• Skin Sensations: Some people experience a patch of skin that feels tender, tingly, numb, or hypersensitive because Wegovy can temporarily change how nerves send sensory signals to the brain. This is harmless and usually resolves on its own. Wear loose-fitting clothes to prevent discomfort.
• Injection Site Reactions: You may experience redness or itching as a localised immune reaction to the needle or medication. It's typically mild. Always rotate your injection sites to reduce irritation.

Serious Wegovy Side Effects You Shouldn’t Ignore

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Serious side effects can occur with Wegovy, but only in rare cases. Get medical advice immediately if you experience the following:

Pancreatitis

Pancreatitis is inflammation of the pancreas, which can happen when taking Wegovy. This weight-loss injection stimulates the pancreas to optimize insulin release and changes how quickly digestion occurs. In rare cases, it can cause a backup or irritation in the pancreatic ducts, triggering inflammation.

You'll experience severe or prolonged stomach pain that spreads to your back and persistent vomiting. If this happens, stop taking Wegovy immediately and seek urgent medical attention. Also, avoid eating and drinking while you wait for help because it can worsen pain and inflammation.

Gallbladder Problems

Rapid weight loss can increase the chance of gallstones and gallbladder inflammation. Your liver excretes extra cholesterol into your bile when you lose weight quickly while taking Wegovy. Too much cholesterol can cause the bile to harden and turn into gallstones.

Warning signs include sudden pain in the upper right side of your stomach, fever, yellowing of the skin or eyes, and pale stools. Don’t ignore severe stomach pain after taking Wegovy, especially if it feels different from your usual side effects.

Kidney Problems

Vomiting and diarrhoea can cause dehydration. This can put extra strain on your kidneys, especially if you already have kidney problems.

With less fluid in your body, your blood pressure drops, meaning your kidneys won't get the blood flow or pressure they need to filter out toxins. If left untreated, your kidneys fail and sustain damage.

Seek immediate help if you feel very weak, dizzy, confused, or if you keep vomiting.

Thyroid Concerns

Patient information leaflets for Wegovy in the UK usually have a warning for Semaglutide, based on animal studies showing a risk for thyroid tumours.

While it's not known whether Wegovy increases thyroid cancer risk in humans, it's best to avoid it if you have a personal or family history of MTC (Medullary Thyroid Cancer) or MEN 2 (Multiple Endocrine Neoplasia Syndrome Type 2). Always speak to your prescriber for the best clinical guidance.

Vision Changes and Eye Risks

If you have type 2 diabetes, rapid changes in blood sugar when taking Wegovy may affect diabetic eye disease.

The fluid balance inside the lens and the blood vessels of your eye is sensitive to the amount of sugar in your blood. When blood glucose drops suddenly, it causes a quick change of fluid out of the tissues of your eyes.

This can temporarily change the shape of your lens, leading to blurred vision. Speak to your prescriber if you notice sudden vision changes or worsening eye symptoms.

Allergic Reactions

Allergic reactions can be mild, often including a rash and itching. You may also notice mild swelling. It often occurs because your body is sensitive to the drug. Some people also experience severe symptoms such as difficulty breathing.

Mild and serious allergic reactions need immediate medical attention. Stop treatment and go to the hospital for assistance.

Wegovy Side Effects Timeline

Wegovy side effects often follow your dosing schedule:

• First Few Weeks: You'll experience nausea, appetite changes, constipation, or diarrhoea when you start treatment. These are all common as your body adjusts to slower digestion and reduced hunger.
• During Dose Increases: Side effects of Wegovy may become more noticeable as you increase your dose. It's why prescribers start you on the lowest amount and gradually increase it. Never increase your dose without speaking to your prescriber first, as your symptoms can affect daily life.
• After Several Months: Side effects usually improve in a few months. Some people still have mild symptoms, especially after eating large meals, drinking alcohol, eating high-fat foods, or eating too quickly.

Note: If symptoms continue, worsen, or feel severe, your prescriber should review your current dose or delay a dose increase. They may also discuss a different course of medication if your side effects are too severe.

Long-Term Side Effects of Wegovy

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People have used Semaglutide for years at lower doses to treat Type 2 diabetes (under the brand name Ozempic). However, its widespread use at a higher dose for long-term weight management is recent. Therefore, the long-term side effects of Wegovy are still being monitored as more people use GLP-1 medicines for weight loss.

Potential Long-Term Risks Being Studied

The MHRA (Medicines and Healthcare products Regulatory Agency), along with other government health regulators and independent scientific bodies across the world, is actively monitoring the following long-term Wegovy risks:

• Gallbladder disease
• Pancreatitis
• Dehydration-related kidney problems
• Nutritional gaps
• Muscle loss
• Hair loss
• Eye complications in people with diabetes

How to Stay Safe Long Term

• Protein First: Eat foods rich in protein first to protect your muscles and prevent hair shedding. High-quality protein sources such as lean meats, fish, eggs, tofu, and Greek yogurt help preserve lean tissue.
• Strength Training: Doing resistance exercises such as lifting weights, using bands, or bodyweight exercises twice a week sends a signal to your body to keep its muscles and burn fat instead.
• Take a Multivitamin: Since you are eating less overall, a daily multivitamin can provide any nutrients you may be missing.
• Aim for Steady Weight Loss: According to Harvard Medical School, losing one to two pounds (about 1 kg) per week is the safest weight loss rate.

Get Wegovy and Clinical Support From Curely

Curely offers Wegovy and other UK-licensed weight-loss injections, such as Mounjaro, as well as weight-loss pills.

We can help you access treatment without in-person GP visits. Our process keeps things simple and private for your weight management goals. You complete a short questionnaire, select medication, and receive your order discreetly at home or at work.

Curely’s flexible model means you can pause treatment or discuss dosage changes without being tied into a rigid plan.

We also offer support throughout your treatment, so you can reach out if you experience adverse effects or are struggling to manage your symptoms. Start your Wegovy journey today, with Curely.

FAQs

How Long Do Wegovy Side Effects Last?

Most common Wegovy side effects improve after a few weeks as your body adjusts. Symptoms may return or become stronger when you increase your dose. Reach out to your prescriber if your side effects last longer than expected or feel severe.

What are the Worst Side Effects of Wegovy?

The most serious side effects include pancreatitis, gallbladder problems, kidney problems from dehydration, and severe allergic reactions. Stop medication immediately and seek help if you experience symptoms such as prolonged stomach pain, difficulty breathing, swelling, or severe vomiting.

What Should I Know Before Taking Wegovy?

You should understand that your food choices and habits matter when taking Wegovy. Small meals, bland foods, drinking plenty of fluids, and avoiding fatty foods can make it easier on your stomach. It’s also worth noting that experiencing side effects doesn't mean that your body has rejected the medication. You may need more time to adjust.

What’s The Worst Day On Wegovy?

Most people feel side effects most strongly in the day or two after the first injection or a dose increase. Others notice the worst symptoms after eating heavy meals and fatty foods. Always monitor what triggers your symptoms so you can manage your side effects.

Can You Drink Alcohol On Wegovy?

Alcohol doesn't react with the medication, but it may worsen nausea, reflux, diarrhoea or low blood sugar risk. If you drink, keep it moderate. Also, avoid alcohol when you're experiencing side effects.

Which Is Safer, Ozempic or Wegovy?

Ozempic and Wegovy both contain Semaglutide, but they're for different uses. Ozempic is licensed in the UK only for managing type 2 diabetes, while Wegovy is specifically licensed for weight management.

Conclusion

Wegovy side effects are commonly gastrointestinal. They're normal and improve as your body adjusts. You can manage symptoms such as nausea, diarrhoea, constipation, headaches, and low energy with better food choices and support from your prescriber.

Serious side effects are less common and warrant quick action. Don’t ignore severe stomach pain, signs of dehydration, allergic reactions, or vision changes.

Curely can help you understand whether Wegovy is suitable and support you throughout your weight loss journey with clinical guidance and flexible treatment.

References

• Feier, Catalin Vladut Ionut, et al. “Assessment of Thyroid Carcinogenic Risk and Safety Profile of GLP1-RA Semaglutide (Ozempic) Therapy for Diabetes Mellitus and Obesity: A Systematic Literature Review.” International Journal of Molecular Sciences, vol. 25, no. 8, 1 Jan. 2024, p. 4346.
• Salamon, Meghan. “What Does a Healthy, Realistic Rate of Weight Loss Look Like, and Why Does It Matter? - Harvard Health.” Harvard Health, 17 Mar. 2026.
• Wharton, Sean, et al. “Once-Weekly Semaglutide 7·2 Mg in Adults with Obesity (STEP UP): A Randomised, Controlled, Phase 3b Trial.” The Lancet Diabetes & Endocrinology, 1 Sept. 2025.
• Wilding, John P. H., et al. “Once-Weekly Semaglutide in Adults with Overweight or Obesity.” The New England Journal of Medicine, vol. 384, no. 11, 10 Feb. 2021, pp. 989–1002. PubMed.