Wegovy Side Effects Explained
Understanding Wegovy side effects
The Wegovy weight-loss injection contains semaglutide, a prescription medicine that acts on GLP-1 receptors involved in appetite regulation. It helps you feel fuller and less hungry. Its effects on the digestive system can also contribute to unwanted symptoms.
Side effects are not a measure of how well treatment is working. You can benefit without feeling sick. Your prescriber assesses progress and tolerability together; do not increase your dose to try to produce stronger side effects. If your main concern is a Wegovy plateau, your prescriber can review progress separately from tolerability.
The figures above describe people reporting symptoms at some point during trials, not the chance of feeling unwell after every injection. They should not be treated as percentages for each starting dose or compared directly with results from unrelated trials.
Common side effects and practical management
The UK leaflet lists nausea, vomiting, diarrhoea, constipation, stomach pain, headache and tiredness as very common: they may affect more than 1 in 10 people. The steps below are for mild symptoms; use the urgent-help advice further down for warning signs.
| Symptom | What may help |
|---|---|
| Nausea | Try smaller portions, eat slowly and stop when comfortably full. Bland foods may be easier to tolerate; avoid greasy meals and foods that trigger symptoms. |
| Vomiting | Take frequent small sips of fluid. Ask a pharmacist about oral rehydration solutions. Seek prompt advice if you cannot keep fluids down; do not wait for a fixed number of days. |
| Diarrhoea | Replace lost fluids and choose foods you tolerate. Seek advice if symptoms are severe, persistent or accompanied by blood, fever or dehydration. |
| Constipation | Increase fibre gradually, drink regularly and keep gently active. Ask a pharmacist if you need treatment. Severe pain, vomiting or a swollen abdomen needs urgent assessment. |
| Reflux, bloating or indigestion | Try smaller meals and avoid lying down straight after eating. Discuss persistent symptoms with a pharmacist or prescriber. |
| Headache or tiredness | Check that you are eating and drinking enough. Persistent, severe or unusual symptoms need assessment rather than being automatically attributed to Wegovy. |
For practical meal choices, see what to eat on Mounjaro or Wegovy. For step-by-step advice on easing nausea, diarrhoea, constipation and reflux, read our guide on how to manage Wegovy side effects. Alcohol may worsen nausea, reflux or dehydration for some people. Read our Wegovy and alcohol guide before drinking during treatment. If you have been advised to restrict fluids because of another condition, follow your clinical team’s advice.
How long do Wegovy side effects last?
There is no reliable timetable for everyone. Digestive symptoms commonly occur during dose increases and many improve as treatment continues, while constipation can last longer. A symptom diary is more useful than expecting nausea to disappear by a particular week.
Record the symptom, its severity, your dose, when it started and whether you can eat and drink normally. Share this with your prescriber before your next increase if symptoms remain troublesome.
During dose increases
Dose escalation is gradual to improve tolerability. Your prescriber may delay an increase or review your dose if symptoms are significant. Follow the Wegovy dose schedule and missed-dose guidance and seek advice before changing treatment.
At 7.2 mg
This higher dose is an option for eligible adults with obesity under a prescriber’s supervision. Digestive symptoms can occur, and altered skin sensations and hair loss are reported more frequently at this dose. Do not assume symptoms will settle within two or three weeks or reduce the dose yourself; discuss troublesome effects with your prescriber.
Other side effects to discuss with your prescriber
| Effect | What to know |
|---|---|
| Injection-site reactions | Mild redness, itching or swelling may occur. Rotate the exact injection spot. Spreading redness, increasing warmth, pain or a reaction that does not improve needs advice. |
| Hair loss | Hair loss is listed in the prescribing information and can also accompany substantial weight loss. Discuss persistent shedding and nutritional intake; recovery timing varies. |
| Dizziness or altered taste | These can occur during treatment. Avoid driving if dizzy. Seek advice if symptoms persist or interfere with daily activities. |
| Changed skin sensation | Tingling, burning or unusual sensitivity can occur, particularly at 7.2 mg. Report troublesome or persistent changes. |
| Low blood sugar | Risk is particularly relevant if you also use insulin or a sulfonylurea. Follow your diabetes team’s monitoring and treatment plan. |
| Fast heartbeat | Tell your prescriber about a racing heartbeat at rest, especially if persistent. Chest pain, collapse or severe breathlessness requires emergency help. |
Use the Wegovy injection instructions alongside your pack leaflet. FlexTouch pens contain four doses; single-dose devices have different instructions. Check your own pen rather than assuming all Wegovy pens work the same way.
Serious symptoms: when to seek urgent help
Difficulty breathing, swelling of the tongue or throat, or collapse needs emergency help. Do not take another dose after a suspected severe allergic reaction unless a clinician advises it.
| Warning sign | Action |
|---|---|
| Severe, persistent abdominal pain, which may spread to the back, with or without vomiting | Stop using Wegovy and seek urgent medical help immediately. This can be pancreatitis. Do not dismiss it as routine nausea. |
| Sudden loss of vision or rapidly worsening eyesight | Seek urgent medical assessment immediately. Semaglutide is associated with a very rare eye condition called NAION; an eye specialist may need to assess you. |
| Severe constipation with abdominal pain, bloating and vomiting | Seek urgent medical help: these can be symptoms of intestinal obstruction. |
| Unable to keep fluids down, very little urine, marked dizziness or confusion | Seek urgent advice from your clinician or NHS 111. Dehydration can affect kidney function; severe illness or collapse needs emergency help. |
| Upper-right abdominal pain, especially with fever or yellow skin or eyes | Seek urgent medical advice for possible gallbladder problems. |
If you have diabetes and existing retinopathy, tell your prescriber and report changes in vision. This is separate from the sudden-vision-loss warning above.
For a suspected side effect, you can also submit a report through the MHRA Yellow Card scheme. Reporting does not replace medical care.
Before starting or continuing treatment
Tell your prescriber about your medical history and all other medicines, including insulin, other weight-loss treatments and anticoagulants. Mention previous pancreatitis, significant digestive problems, kidney disease and any planned procedure involving anaesthesia or deep sedation.
Wegovy should not be used during pregnancy or breastfeeding. Discuss pregnancy plans before treatment: semaglutide needs to be stopped at least two months before a planned pregnancy.
Do not use Wegovy if you are allergic to semaglutide or an ingredient. Discuss thyroid disease or a relevant family history with your prescriber.
Frequently asked questions
Which Wegovy dose causes the most nausea?
Can I take anti-sickness medicine?
Does having no side effects mean Wegovy is not working?
Should I inject at night to avoid side effects?
Will I need to stop treatment?
Can Wegovy affect my mental health?
Is Wegovy safe long-term?
Sources checked 12 October 2026. General information; your pack leaflet and individual clinical advice remain important.
Medically Reviewed by Our GPhC-Registered Pharmacists
This guide was medically reviewed for accuracy, safety and alignment with UK clinical standards. Learn about our medical review process >
Content last updated: 12 October 2026 · Next review: November 2026