A complete guide to Wegovy side effects

Is Wegovy Safe?

Yes, Wegovy is considered safe when used as prescribed. It was approved by SAHPRA for use in South Africa in March 2025 and has been used by thousands of people worldwide to manage their weight.

For certain people with existing heart disease but no diabetes¹, Wegovy may also help lower the chance of major cardiovascular problems, including heart attacks and strokes.

Like all medicines, Wegovy has risks as well as benefits. Serious side effects can occur, although they are uncommon. Your healthcare provider will carry out a thorough assessment before prescribing Wegovy to make sure it's appropriate for you. It's important to be honest about your medical history during this process.

Who cannot take Wegovy?

While Wegovy is safe for most people, it is not suitable for everyone. You should not use Wegovy if you:

Please see the SAHPRA Wegovy approved professional information for further information: https://www.sahpra.org.za/registered-health-products/

• Are under 18 years of age
• Are pregnant, trying to get pregnant, or breastfeeding
• Have type 1 diabetes
• Have a history of pancreatitis
• Have a personal or family history of certain thyroid cancers (such as medullary thyroid carcinoma) or a rare genetic condition called MEN2 syndrome
• Have a known allergy to semaglutide or any other ingredient contained in Wegovy

Common Side Effects of Wegovy

Most side effects from Wegovy affect the stomach and digestive system, particularly when starting treatment or increasing the dose. These usually settle down over time.

Very common (affecting more than 1 in 10 people):

Other common side effects (affecting up to 1 in 10 people):

• Nausea (feeling sick)
• Vomiting
• Diarrhoea
• Constipation
• Stomach pain
• Headache
• Fatigue (feeling weak or tired)
• Dizziness
• Indigestion or upset stomach
• Burping or gas
• Bloating
• Heartburn or reflux (sometimes called gastro-oesophageal reflux disease or GORD)
• Gastritis (inflammation of the stomach lining, which may cause stomach pain, nausea, or vomiting)
• Gallstones
• Hair loss
• Injection site reactions, including redness, itching, or swelling
• Changes in how food or drinks taste
• Unusual skin sensations
• Low blood sugar (hypoglycaemia) or eye problems related to diabetes (diabetic retinopathy) – mainly in people with type 2 diabetes

When Do Wegovy Side Effects Start?

Most people who experience side effects notice them at the beginning of treatment or when their dose is increased. Semaglutide levels in your body are typically at their highest about two to three days after each injection, so this is when side effects are most likely to be noticeable.

How Long Will Side Effects Last When Using Wegovy?

For most people, side effects begin to ease as the body gets used to the medicine. However, this varies from person to person. Some people take longer to adjust, and others may find it harder to build tolerance.

If your side effects are not improving or seem to be getting worse as you move through your Wegovy programme, talk to your healthcare provider for advice.

How Long Does Wegovy Stay in Your System?

Understanding how long Wegovy stays in your system can help you know what to expect if you decide to stop treatment. Semaglutide has a half-life of about seven days, which means the amount of the active ingredient in your body reduces by half every week. After your last dose, it can take a further five to seven weeks for semaglutide to fully leave your system.

This means that if you stop taking Wegovy, any side effects may continue for several weeks before they ease completely. Please note: Do not stop using Wegovy without consulting your healthcare provider.

Can Wegovy Make You Tired?

Tiredness (fatigue) is a common side effect of Wegovy treatment. While it's not fully understood why Wegovy causes tiredness, there are several possible reasons:

You're eating less

Wegovy works by reducing your appetite, which means you're likely eating fewer calories than before. It can take a while for your body to get used to eating less, and this adjustment may leave you feeling low on energy, particularly during the first few weeks.

Other side effects may be contributing

Side effects such as nausea, vomiting, or diarrhoea can be draining on the body. If you're experiencing several of these at once, it's natural to feel more fatigued than usual.

Wegovy may affect your hormones

Semaglutide mimics a hormone (GLP-1) that influences several systems in your body, including metabolism and energy regulation. These hormonal changes may contribute to feelings of tiredness as your body adapts.

Your sleep may be affected

Some people notice changes in their sleep patterns when starting Wegovy. Poor quality sleep or disrupted sleep can lead to daytime tiredness.

Low blood sugar

If you're eating significantly less or if you have type 2 diabetes and take other blood sugar–lowering medicines, your blood sugar may drop lower than usual. Low blood sugar (hypoglycaemia) can cause tiredness, shakiness, and difficulty concentrating. If you think this may be happening, talk to your healthcare provider.

What can help:

To reduce tiredness, try to eat balanced, nutritious meals even if your portions are smaller, and stay well hydrated throughout the day. Keeping a regular sleep routine can also make a difference. If tiredness persists or becomes severe, speak to your healthcare provider.

Can Wegovy Cause Headaches?

Yes, headaches are a common side effect of Wegovy treatment. There are several factors that may contribute:

Dehydration

When your appetite decreases, you may also drink less without realising it. Dehydration is a common cause of headaches. If you're also experiencing vomiting or diarrhoea as side effects, this can further increase the risk of becoming dehydrated.

Other contributing factors

Headaches can also be triggered or made worse by alcohol, stress, or disrupted sleep, all of which may be more noticeable when you're adjusting to a new treatment.

What can help:

• Stay well hydrated by drinking water regularly, even when you don't feel thirsty
• Limit or avoid alcohol
• Try to keep a regular sleep routine
• Gentle exercise like a short walk or stretch can ease headache symptoms
• If headaches are persistent or severe, talk to your healthcare provider

Do I Need to Avoid Certain Foods?

Wegovy works best when used alongside a healthy lifestyle, so what you eat matters. Eating plenty of whole foods – including fruit, vegetables, lean meats, good fats, and high-fibre options – can support your weight-loss goals and may help ease some common side effects. You don't need to give up your favourite treats entirely, but cutting back on foods high in refined sugar, trans fats, and salt is a good idea.

Some foods are more likely to trigger or worsen side effects while you're on Wegovy. Greasy, high-fat foods can make nausea, indigestion, and heartburn worse. Sugary foods and drinks – especially on an empty stomach – may increase nausea and bloating. Ultra-processed snacks like potato chips can upset your digestion, and their high salt content may cause fluid retention. Foods like white bread and pastries are high in carbohydrates but low in fibre, which your body needs for healthy digestion and regular bowel movements.

If you're unsure what changes to make, your healthcare provider or a registered nutritionist can help you build a balanced eating plan that works with your Wegovy treatment.

Does Wegovy Cause Heartburn?

Yes, heartburn (also known as acid reflux or gastro-oesophageal reflux) is a common side effect of Wegovy. Because Wegovy slows digestion, food stays in your stomach for longer than usual. This can increase the chance of stomach acid rising into your oesophagus, causing that familiar burning sensation.

Eating smaller meals, limiting acidic, fatty, or spicy foods, and staying upright after eating can all help reduce heartburn. Staying hydrated and reducing your intake of alcohol and caffeine can also help. If you smoke or vape, try to cut down or stop as both can cause acid to travel up your digestive tract and make reflux worse.

If lifestyle changes aren't enough, over-the-counter antacids such as Gaviscon or Quickeze can offer short-term relief by neutralising stomach acid. For longer-lasting support, treatments like Losec or Nexium are available from pharmacies. Your pharmacist can advise on the most suitable option for you. Speak to your healthcare provider if heartburn continues or becomes more severe.

Wegovy and Stomach Pain

Besides heartburn, Wegovy can cause other stomach-related discomfort as your body adjusts to changes in digestion. General stomach pain, bloating, and cramping are common and usually settle over time.

In rare cases, Wegovy may cause a more serious condition called pancreatitis (inflammation of the pancreas). Signs of pancreatitis include severe, long-lasting pain in your stomach that may radiate towards your back. Vomiting may or may not occur. If you experience these symptoms, seek medical attention immediately.

Gallstones are another possible side effect. Symptoms can include sudden, intense abdominal pain, nausea, or changes in urine colour. If you notice any of these, speak to your healthcare provider.

Wegovy and Diarrhoea

Diarrhoea is a common side effect of Wegovy, caused by changes in the way your digestive system processes food. Not everyone experiences it, but if you do, a few simple changes can help manage symptoms:

Stay hydrated. Diarrhoea can lead to dehydration, so drink plenty of water throughout the day. Diluted fruit juice or rehydration drinks such as Enerlyte can help replace lost fluids and electrolytes.

Eat bland, easy-to-digest foods. Simple foods like bananas, plain rice, stewed apples, and dry toast are easy for your stomach to handle. Plain boiled potatoes, crackers, and rolled oats are also good options. Stick to these for a day or two until symptoms ease.

Limit foods and drinks that can make it worse. Fatty, fried, and spicy foods may irritate your gut. High-fibre foods can also aggravate diarrhoea. If you're lactose intolerant, avoid dairy. Cut back on coffee, sugary drinks, and alcohol, which can worsen dehydration.

Try light movement. Gentle activity such as a short walk, light housework, gardening, or yoga can improve blood flow to your digestive system and help ease symptoms. Avoid anything too intense until you're feeling better.

Over-the-counter medicines such as loperamide (Imodium) can provide short-term relief but should only be used briefly. If diarrhoea continues for more than a few days or gets worse, talk to your healthcare provider.

Can Wegovy Cause Hair Loss?

Some people notice hair loss while using Wegovy, but there is no direct evidence that the medicine itself causes it. Hair loss is more likely to happen when you lose weight quickly or make sudden changes to your diet. When this happens, your body may put hair growth on hold while it adjusts.

This type of hair loss is called telogen effluvium, and the good news is that it's usually temporary. Hair growth typically returns to normal once your body adjusts to your new weight and you're eating a stable, balanced diet with a good range of nutrients.

To reduce the risk, aim for gradual, steady weight loss rather than rapid results, and make sure you're getting enough protein, vitamins, and minerals from your food. If hair loss continues or concerns you, talk to your healthcare provider.

Does Wegovy Cause Vaginal Dryness?

There's no direct evidence that Wegovy causes vaginal dryness. However, hormonal changes that can occur during weight loss may affect vaginal health in some people.

Vaginal dryness can be triggered by many things, including rapid weight loss, menopause, breastfeeding, and certain medications. It's also possible that dehydration from side effects like vomiting or diarrhoea may contribute.

If you experience vaginal dryness while using Wegovy, staying well hydrated may help. Over-the-counter lubricants and moisturisers are available from pharmacies. If it persists or affects your quality of life, talk to your healthcare provider.

Uncommon Side Effects of Wegovy

The following side effects are uncommon, affecting up to 1 in 100 people:

If you experience any of the above symptoms, such as jaundice or increased heart rate, contact your healthcare provider immediately.

• Increased heart rate
• Higher levels of pancreatic enzymes (lipase and amylase) detected in blood tests
• Low blood sugar (hypoglycaemia)
• Increased bilirubin in the blood, which may cause jaundice (yellowing of the skin or whites of the eyes)

Serious Side Effects of Wegovy

Serious side effects are uncommon, but it's important to know what they are so you can recognise the symptoms.

Consult your healthcare provider immediately if you experience any of the above symptoms.

• Acute pancreatitis (inflamed pancreas): This may affect up to 1 in 100 people. Symptoms include severe, long-lasting stomach pain that may spread to your back, with or without vomiting. If you experience this, see your doctor immediately.
• Gallstones: Symptoms can include sudden, intense pain in your upper abdomen, nausea, or pain between your shoulder blades.
• Severe allergic reactions (anaphylaxis): This is rare (up to 1 in 1,000 people). Seek immediate medical help if you experience trouble breathing, swelling of your face, lips, tongue, or throat, wheezing, a fast heartbeat, pale or cold skin, or feeling dizzy or weak.
• Hip fractures: Rare, but one clinical trial found hip and pelvic fractures were reported more often in people taking Wegovy. Other research suggests this may be linked to rapid weight loss rather than the medicine itself. This is another reason why gradual, steady weight loss and a balanced diet are important.
• Severe constipation: In rare cases, Wegovy may cause a severe form of constipation with symptoms such as stomach pain, bloating, and vomiting.

Feeling Sick on Wegovy

Nausea is one of the most common side effects of Wegovy, particularly in the early stages of treatment or when your dose increases. The good news is that it usually improves as your body adjusts. In the meantime, there are steps you can take to ease symptoms.

Having several small meals spread across the day instead of two or three big ones is easier on your stomach and can help reduce nausea. Choose foods that are gentle on the stomach – plain options like rice, bananas, toast, and crackers work well. Try to avoid fatty, greasy, or highly acidic foods, and keep track of anything that seems to trigger nausea so you can avoid it.

Ginger can also help. It contains a natural compound called gingerol, which has a calming effect on the stomach. You can try ginger tea, ginger chews, or adding fresh ginger to meals.

Getting outside for a walk in the fresh air can make a difference too. Light movement and a change of scenery often help ease that queasy feeling.

If nausea is affecting your daily life, anti-nausea medicines are available from your pharmacy, but these are only a short-term solution. If symptoms persist, speak to your healthcare provider for further advice.

Managing Injection Site Reactions

Around 1 in 10 people using Wegovy experience some reaction at the injection site. This is usually mild and tends to improve as your body gets used to the medicine. Symptoms to look out for include redness, itching, swelling, or bruising around the area where you injected.

A few simple steps can help minimise irritation. Rotating where you inject – between your stomach, upper arm, and upper thigh – gives each site time to recover. Applying an anti-itch cream such as Anthisan or Dermal Therapy can help soothe the area. Some people also find that taking a non-drowsy antihistamine about 30 minutes before injecting helps prevent a reaction.

If any injection site reaction becomes worse, spreads, or is painful, do not continue to use the affected area and contact your healthcare provider.

Interactions and When to Avoid Wegovy

Some medications, supplements, and substances may interact with Wegovy or make side effects worse. Certain health conditions may also make Wegovy unsuitable for some people.

Other medications

There are no major direct interactions between Wegovy and other medicines. However, because Wegovy slows digestion, it may affect how quickly your body absorbs some medications – especially during the early stages of treatment or after a dose adjustment.

This is especially important for medicines where the dose needs to be very precise, such as warfarin (a blood thinner) or insulin. With these types of medicines, even small changes in how they're absorbed can cause problems.

Side effects like vomiting or diarrhoea can also affect how well your body absorbs other medicines. If you're vomiting, your medication may not be absorbed at all. Dehydration from diarrhoea can concentrate medicines in your system, increasing the risk of side effects.

If you're taking any regular medication and experience persistent vomiting or diarrhoea while using Wegovy, speak to your healthcare provider for advice.

Is There a Link Between Wegovy and Cancer?

You may have seen headlines linking Wegovy to cancer, so it's worth understanding what the research actually shows.

In animal studies, GLP-1 medicines like semaglutide were found to cause thyroid tumours in rodents. However, this effect has not been seen in humans, and there is currently no evidence that Wegovy causes thyroid cancer in people.

As a precaution, Wegovy is not recommended for anyone who has had, or has family members who have had, certain types of thyroid cancer, including medullary thyroid carcinoma (MTC) or a rare condition called multiple endocrine neoplasia syndrome type 2 (MEN2). Your healthcare provider will ask about your medical history before prescribing Wegovy.

If you would like to know more about diseases and cancers that affect the thyroid, please see https://www.thyroid.nz/index

What Are the Long-Term Side Effects of Wegovy?

Based on current clinical evidence, there are no major safety concerns with using Wegovy over the long term.

Many people continue using Wegovy beyond their initial weight-loss phase to help maintain their results. Staying on the medicine during this maintenance period can support the healthy habits you've built and make it easier to manage your weight over time.

If you reach your goal weight, that doesn't necessarily mean you need to stop taking Wegovy. Your healthcare provider can discuss whether continuing treatment is right for you based on your individual situation and how well you're responding to the medicine.

Getting Support for Wegovy Side Effects

Before you start Wegovy, your healthcare provider will review your medical history to make sure it's safe for you to use. They'll also explain what side effects you might experience and what to expect during treatment.

If side effects occur, talk to your healthcare provider. They can often adjust your dose or suggest ways to manage symptoms while your body gets used to the medicine.

If you have any concerns at all – whether about side effects or anything else related to your treatment – don't hesitate to get in touch with your healthcare provider. They're there to support you throughout your weight-loss journey.

You might also consider joining a weight-loss support group or working with a nutritionist or personal trainer. These services can help you stay on track with your goals and provide extra encouragement along the way.

Wegovy® is used for weight loss and weight maintenance in addition to diet and physical activity in adults and adolescents aged 18 years and above who meet certain Body Mass Index (BMI) criteria. Wegovy® is also indicated to reduce the risk of a heart disease–related event in addition to standard of care if you are an adult with a history of heart disease and have a BMI ≥27 kg/m² without established diabetes. Wegovy® contains the active ingredient semaglutide and is available in the following dose forms: 0.25 mg, 0.5 mg, 1.0 mg, 1.7 mg and 2.4 mg. The two lower-dose pens contain 1.5 mL of liquid each, while the three higher-dose pens contain 3 mL each. Wegovy® has risks and benefits. Ask your healthcare provider if Wegovy® is right for you. Use strictly as directed. If you experience side effects, see your doctor, pharmacist, or healthcare professional. Side effects of Wegovy® include nausea, vomiting, diarrhoea, constipation, abdominal pain, headache, and fatigue. Please refer to the Wegovy® approved professional information available at: https://www.sahpra.org.za/registered-health-products/

Footnotes

1. Wegovy’s cardiovascular indication is based on the SELECT trial, a large, randomised trial of semaglutide 2.4 mg once weekly in adults with overweight or obesity and established cardiovascular disease who did not have diabetes. Because the trial excluded people with diabetes, the label for this specific heart-disease indication also specifies “do not have diabetes.” This reflects the study design, not a universal rule that semaglutide cannot be used in people with diabetes.

Important safety information

Prescription medicine.