Wegovy shot side effects: what most people experience, and what needs urgent attention

Step 1: the first few weeks, your digestive system is adjusting

Wegovy slows the rate at which your stomach empties food into the small intestine. That mechanism is central to how it reduces appetite, but it also explains why the gut often pushes back early on. Nausea is the most frequently reported symptom, followed by loose stools, constipation, burping and stomach discomfort. Some people notice these from the very first injection; others sail through the starter doses and only feel them when the dose increases.

A question our prescribers hear most weeks is whether nausea means the treatment isn't working or isn't right for you. Usually it doesn't. The low starting dose exists specifically to give your system time to adjust, and the titration schedule (moving up roughly every four weeks) is designed to reduce the chance of a sudden step-change that overwhelms you. Eating smaller portions, staying upright after meals, and avoiding very fatty or spicy food can all help take the edge off.

Headache and fatigue also appear more often in the early weeks. If you're finding tiredness persistent, it's worth reading about fatigue after the Wegovy shot, there are practical reasons it happens and practical ways to manage it. Similarly, if headaches are a pattern, there's specific guidance on headaches after the Wegovy shot that may help.

The NHS semaglutide medicine page lists the common, uncommon and rare side effects with their approximate frequencies, a useful cross-reference alongside your patient information leaflet.

Step 2: dose increases, expect side effects to revisit you

Wegovy's maintenance schedule takes several months to reach. Each time the dose steps up, many people experience a brief return of GI symptoms, even if the previous dose had become entirely comfortable. This is normal. The pattern typically mirrors what happened at the start: a few days of nausea or loose stools, then gradual settling.

The practical implication: plan dose-increase weeks sensibly. If you have a big event, a long journey or a stressful work deadline, it's worth discussing with your prescriber whether the timing works for you. Treatment is not one-size-fits-all in its schedule, and what to do if you're unwell on injection day is a genuine decision that deserves proper guidance rather than a guess.

Injection-site reactions (redness, mild swelling or itching where you inject) are also more likely after dose changes. Rotating between your abdomen, thigh and upper arm, and making sure the skin is clean, reduces this. If a site reaction is spreading, warm, or doesn't settle within a couple of days, contact your prescriber.

For a broader picture of how the safety profile sits overall, our safety overview for the Wegovy shot covers the evidence in more detail.

Step 3: symptoms that need prompt medical attention

Most Wegovy side effects are an inconvenience rather than a danger. A smaller number require you to act quickly.

Acute pancreatitis is rare but serious. In January 2026 the MHRA published a Drug Safety Update specifically highlighting pancreatitis as a known risk with GLP-1 medicines: the warning sign is severe, persistent abdominal pain that may spread to the back, with or without vomiting. Stop your injection and get emergency care if this happens, do not wait for it to settle on its own.

Gallbladder problems (gallstones and inflammation) appear more often in people losing weight rapidly on any treatment, including Wegovy. Steady pain in the upper right abdomen, especially after eating, or pain that builds over hours rather than minutes, warrants same-day medical review.

Severe dehydration from persistent vomiting or diarrhoea can affect kidney function. If you cannot keep fluids down for more than 24 hours, seek medical advice promptly, this applies whether the cause feels Wegovy-related or not.

Signs of a serious allergic reaction (swelling of the face, lips or throat, difficulty breathing, widespread rash) require immediate emergency care. And if you notice any change in mood, low feelings or thoughts of self-harm after starting treatment, speak to your GP or prescriber that day.

Any unexpected reaction can be reported to the MHRA's Yellow Card scheme, reports from patients, not just clinicians, help build the safety picture for everyone using these medicines.

Step 4: managing side effects and deciding whether to continue

The full side-effect profile of Wegovy, including less common reactions, is documented in the patient information leaflet inside every pack and on the Wegovy side effects page on this site. The leaflet from the manufacturer is the authoritative reference; read it before your first injection, not after.

If side effects are making treatment genuinely difficult, your prescriber has options. Slowing the titration (staying at a lower dose for longer) is a recognised approach. Stopping temporarily during illness is sometimes appropriate. What matters is that these decisions are made with clinical input, not alone.

At nume, our prescribers review every repeat order, not just the first consultation. That ongoing review is the right time to raise side effects that are bothering you, ask about adjustments, or discuss whether the balance of benefit and discomfort makes sense for you. You can also reach our aftercare team seven days a week via our contact page. Speak to our prescribers about your situation, it's a proper clinical conversation, not a tick-box exercise.