All Side Effects of Wegovy: What to Expect and When to Act

The first few weeks: what most people actually feel

Picture this: you have just administered your first Wegovy dose on a Saturday morning, and by the afternoon your appetite has dropped noticeably. By Sunday, though, you feel a low-grade nausea that makes the idea of a full roast unappealing. That experience (real appetite suppression alongside digestive discomfort) is what many people describe in the early weeks of treatment.

The most frequently reported Wegovy side effects are gastrointestinal. Nausea tops the list, followed by vomiting, diarrhoea, constipation, indigestion and burping. Headache, fatigue and dizziness also appear commonly. These effects tend to peak in the 24 to 48 hours after each injection and ease as the week goes on. After a dose increase, the cycle often repeats briefly before settling again.

Eating smaller portions, avoiding very fatty or spicy food, and staying well hydrated all help the digestive side effects feel more manageable. Some people find that injecting in the evening means any nausea passes overnight. Small, practical adjustments like these can make a meaningful difference, and our prescribers discuss them as part of the consultation process, you can read more about how side effects of Wegovy tend to progress over time.

Injection-site reactions (redness, mild bruising, itching) are also common and usually resolve quickly. Rotating the injection site each week between the abdomen, thigh and upper arm reduces their frequency.

Less common effects worth knowing about before you begin

Beyond the GI effects, a smaller proportion of people taking Wegovy notice other changes. Hair thinning has been reported during significant weight loss on GLP-1 medicines generally; it is thought to be related to the physical stress of rapid body-weight change rather than semaglutide acting directly on hair follicles, and it typically reverses over time. Heart rate increases have also been observed, which is relevant if you have a pre-existing cardiac condition.

Gallbladder problems, including gallstones, are a recognised but less common side effect. Rapid weight loss of any kind (not just from medication) can promote gallstone formation, so the risk is not unique to Wegovy, though it is real. If you notice pain in the upper-right abdomen, particularly after eating, tell your GP or prescriber promptly.

Low mood and, in rare cases, thoughts of self-harm have been reported with GLP-1 medicines. The MHRA continues to monitor this signal. If your mood changes noticeably after starting treatment, contact your prescriber or GP the same day, or call 111. You can find further detail on the rarer side effects of Wegovy and what the current evidence says about each one.

For anyone curious about whether some people experience all wegovy side effects at once or none at all, the honest answer is that responses vary considerably. If you want to understand what a single side effect of Wegovy actually feels like in practice, individual metabolism, starting dose, and other medicines all play a role, which is exactly why clinical review before starting matters.

When to get medical help without delay

Most side effects of taking Wegovy are uncomfortable rather than dangerous. A few, however, need prompt attention.

Call 999 or go to A&E if you experience: a severe allergic reaction (swelling of the face, lips or throat; difficulty breathing; rapid heartbeat); severe stomach pain that spreads to your back, with or without vomiting. That last symptom pattern is the signature of acute pancreatitis, which the MHRA highlighted in a Drug Safety Update published in January 2026 as a known but infrequent serious risk of GLP-1 medicines. It is rare. Knowing the warning sign before you ever need it is the point.

Contact your GP or prescriber the same day (or call 111) for: persistent vomiting or diarrhoea causing dehydration (signs include dark urine, dizziness on standing, very little urination); gallbladder-type pain as described above; significant mood changes or self-harm thoughts; any sudden changes in vision if you have diabetes.

If you become severely dehydrated while vomiting, your kidneys can be affected, drink small sips of water frequently and seek help if you cannot keep fluids down for more than a few hours. You can also explore the more serious Wegovy side effects in greater depth, including how they have been managed in clinical practice.

The Yellow Card scheme is the right place to report any suspected side effect (serious or otherwise) while on treatment. Reports from real patients are how the MHRA builds its ongoing safety picture for medicines like Wegovy, and submitting one at yellowcard.mhra.gov.uk takes only a few minutes.

Side effects in the context of clinical supervision, and what comes next

Wegovy is a once-weekly injectable treatment licensed in the UK for weight management. It is a prescription-only medicine, which means clinical oversight is part of the process by design, not an optional extra. At nume, a GPhC-registered Independent Prescriber (a real clinician, not a decision algorithm) reads your consultation before any prescription is issued. They assess your medical history, current medicines and any factors that might affect how you respond to semaglutide. Our clinical team also provides priority aftercare seven days a week if you have questions once treatment is underway.

Some people find they get through treatment with minimal disruption. Others find the first month uncomfortable. Understanding all Wegovy side effects (common, uncommon and rare) before you start means you are not alarmed by the expected or dismissive of the significant. That balance is what good prescribing support looks like.

If you are weighing up treatment options more broadly, our weight-loss treatment overview covers the alternatives and how they compare. And if a specific effect you have read about is giving you pause, our frequently asked questions page may address it directly, or you can contact our team before committing to a consultation.

If you are ready to talk to a prescriber about whether Wegovy is right for you (including any side-effect concerns) start your free consultation and get a same-day clinical review.