Potential Side Effects of Wegovy: Making an Informed Decision

The most common side effects and why they happen at the start

Nausea is the side effect people mention most often, and there is a straightforward reason for it: Wegovy slows the rate at which the stomach empties, so food sits there longer than your body is used to. The NHS semaglutide medicines page lists nausea, vomiting, diarrhoea, constipation, indigestion, burping, and stomach discomfort as common effects, common meaning reported by more than one in ten people in clinical trials. Fatigue, headache, and dizziness also appear, particularly in the early weeks.

Most people find these effects are worst during the dose-escalation phase and calm down once the body adjusts. That is partly why the titration schedule exists: starting at a lower dose and moving up gradually gives your system time to adapt. What happens in those first weeks specifically is worth reading if you are at the very beginning of treatment. Practical steps (eating smaller portions, avoiding fatty or spicy food, staying hydrated) can make a real difference to how you feel day to day, though your prescriber or the Patient Information Leaflet is the right place for personalised guidance.

Injection-site reactions (redness, mild swelling, itching at the injection point) are also reported. Rotating the injection site each week reduces the likelihood of localised irritation building up.

Less common effects that are still worth knowing about before you decide

Some people experience mood changes on semaglutide. The evidence is still being evaluated, but it is a question that comes up regularly, our prescribers hear it most weeks. If you are curious about whether Wegovy can affect mood, there is a dedicated page covering what is currently known. Separately, bloating is something a number of people report, particularly during the adjustment period; bloating as a side effect of Wegovy is addressed in its own right if that is a concern for you.

Gallbladder-related problems, including gallstones, are listed in the prescribing information as an uncommon risk, relevant if you have a personal or family history of gallstones. Hair thinning is sometimes reported; this is thought to be linked to rapid calorie reduction rather than to semaglutide itself, which means protein intake and the pace of weight loss both matter. Pulse rate increases have been observed in some participants in clinical trials, so people with existing cardiac conditions should discuss this with their prescriber before starting. A full rundown of reported side effects across the semaglutide trials goes into greater depth on these less-discussed effects.

Wegovy is not recommended during pregnancy, while breastfeeding, or if you are trying to conceive. It is not licensed for under-18s. These are not fine-print caveats; they are absolute contraindications that your prescriber will ask about directly.

When to get medical help without delay

Most people on Wegovy will not experience anything serious. But certain symptoms should not be waited out or managed at home. Seek urgent medical attention for any of the following.

Severe stomach pain that does not ease (particularly if it spreads to your back, with or without vomiting) can be a sign of acute pancreatitis. In January 2026, the MHRA published a Drug Safety Update specifically drawing prescribers' and patients' attention to this risk with GLP-1 medicines. It is infrequent, but it can be serious, and it needs prompt assessment rather than self-management.

Other symptoms that warrant prompt contact with a doctor or emergency services: signs of a severe allergic reaction (swelling of the face, throat, or lips; difficulty breathing; rapid heartbeat), symptoms of significant dehydration from prolonged vomiting or diarrhoea (confusion, very dark urine, inability to keep fluids down), or sudden changes in vision. If you are also treated for type 2 diabetes, watch for symptoms of low blood sugar, which can occur when semaglutide is combined with certain other medicines.

You can report any suspected side effect (whether you think it is definitely linked to Wegovy or not) through the MHRA Yellow Card scheme. This reporting helps regulators monitor medicines in real-world use and contributes to the evidence base for future patients.

What this means for your decision, and where our prescribers come in

Reading a side-effect list can feel alarming, even when the risks are small. That is understandable. What helps is having the whole picture: how common each effect actually is, how it tends to resolve, and how it compares to the documented health risks of untreated obesity. That is a conversation, not a checklist, and it is exactly what a clinical consultation is for.

At nume, a GPhC-registered Independent Prescriber reads your answers personally and assesses suitability based on your full health picture, not a generic algorithm. If Wegovy is not right for you, they will say so; if it is, they will talk through what to expect and how to manage it. You can explore what is included in the process on our weight-loss treatments page, or read about the more serious end of the side-effect spectrum if that is what you want to understand first. Either way, starting with the broader picture of weight-loss treatment options can help frame the decision.

Speak to our prescribers as part of your free consultation, side effects, your medical history, and your questions are all part of what gets discussed before anything is prescribed.