Wegovy side effects on the NHS and in private treatment: what to expect

Step 1, the first four weeks: settling in at the starter dose

Wegovy treatment begins at 0.25 mg weekly. That starting dose exists mainly to let your digestive system adapt; the gradual titration schedule is designed precisely to reduce the intensity of side effects rather than rush towards a therapeutic level.

During these early weeks, nausea is the most common complaint. Some people also notice burping, a feeling of fullness that arrives quickly during meals, or mild constipation. Fatigue and headache appear in some people too, particularly in the first week or two. For most, these symptoms are mild and sporadic rather than constant.

Practical things that genuinely help: eating smaller portions, avoiding fatty or heavily spiced food, staying well hydrated, and not lying down immediately after eating. Our prescribers go through this in more detail as part of the consultation, and there is further practical guidance on managing Wegovy side effects day to day if you want to read ahead.

One note on timing: if you are due a dose increase and a bank holiday falls in the same week, do not guess at what to do, check with your prescriber before moving up. A Monday order placed just before a holiday is still processed by a clinician that day if received before 12pm, but plan ahead if your routine is disrupted.

Step 2, dose increases: when side effects may return briefly

The titration schedule moves through 0.5 mg, then 1.0 mg, 1.7 mg and up to 2.4 mg (or, for those on the approved 7.2 mg pathway, further still), with roughly four weeks at each level. Each step up can bring a brief return of the early nausea or loose stools, typically lasting a few days. This is normal and expected, not a sign that something has gone wrong.

What matters is the pattern. Side effects that are improving, even slowly, are different from ones that are getting worse or lasting longer than two weeks without any let-up. If the latter is happening, that is a conversation to have with your prescriber before the next dose change, not something to push through on your own.

People who access Wegovy through an NHS specialist weight management service will have a multidisciplinary team to turn to at these moments. Those on a private prescription should have equivalent clinical support available; at nume, aftercare is available seven days a week specifically for this.

It is also worth noting that the NHS semaglutide page lists the full frequency classification for side effects, from very common to rare, so you can calibrate what you read online against the actual evidence base.

Step 3, ongoing treatment: less common but more serious effects to know about

Beyond the GI effects, a smaller number of people on semaglutide experience side effects that are less frequent but more significant. Gallbladder problems (including gallstones) are a recognised risk, particularly with rapid weight loss, and symptoms include pain in the upper right abdomen, sometimes with fever or yellowing of the skin. These need medical assessment.

Acute pancreatitis is uncommon but serious. In January 2026 the MHRA issued a Drug Safety Update highlighting this risk across GLP-1 medicines: the symptom to act on is severe, persistent stomach pain that radiates to the back, with or without vomiting. Do not wait to see if it passes, seek urgent medical help. You can read the MHRA's full communications via the MHRA Drug Safety Update index.

Mood changes and thoughts of self-harm, while rare, are listed in the safety data. If you notice significant low mood, tell your GP or prescriber promptly. The same applies to any allergic reaction, swelling of the face, throat or tongue, difficulty breathing, or a rapidly spreading rash all need emergency care.

A full list of contraindications and warnings, including thyroid concerns and the interaction with certain medications, is set out in the Wegovy Patient Information Leaflet, available on the electronic Medicines Compendium (eMC). Always read it before you start.

When to get medical help: a plain summary

Contact your GP or prescriber the same day, or attend urgent care, if you experience any of the following: severe or persistent stomach pain spreading to your back; signs of a gallbladder problem (upper-right abdominal pain, fever, jaundice); significant dehydration from repeated vomiting or diarrhoea; symptoms of an allergic reaction; sudden changes in vision; or notable low mood or thoughts of self-harm.

Call 999 or go to A&E if you have difficulty breathing, chest pain, or a severe allergic reaction.

For anything less urgent (side effects that are uncomfortable but manageable, questions about whether to skip a dose, or worries about a dose increase) your prescriber is the right first call. If you are exploring whether Wegovy is suitable for you and want to understand the BMI thresholds that apply under NHS and private eligibility criteria, that is covered separately.

Suspected side effects can be reported to the MHRA directly at yellowcard.mhra.gov.uk, you do not need a clinician to do this for you, and reports from patients are genuinely valuable for ongoing safety monitoring. If you would like to learn more about how semaglutide fits into the NHS weight management landscape, or are weighing up whether you qualify for Wegovy on the NHS, those pages go into the specifics. And if you are considering a private route after reading this, you can find out how to buy Wegovy and speak to our prescribers, who discuss suitability and side effects as part of every free consultation, not as a box to tick.