Does Wegovy Have Side Effects — and How Do You Weigh Them Up?

The side effects that most people experience (and when they tend to peak)

The majority of people who take Wegovy notice some gastrointestinal discomfort, especially in the first four to eight weeks. The NHS medicines page for semaglutide lists nausea as the most frequently reported effect, followed by vomiting, diarrhoea, constipation, indigestion, burping and stomach pain. Headache, fatigue and dizziness also appear in the trial data, though less often.

Timing matters here. These effects are almost always at their worst right after a dose increase, because the medicine is working harder on the receptors that slow gastric emptying and reduce appetite. For most people, the discomfort fades within a week or two once the body has adjusted. Eating smaller meals, staying well hydrated and avoiding rich or fatty foods around the time of the injection can all help, something worth raising with your prescriber if you're finding a particular dose difficult.

Injection-site reactions (redness, itching or swelling at the injection point) are also reported, though these are usually mild and short-lived. Rotating between the abdomen, thigh and upper arm reduces the likelihood of localised irritation building up.

It's worth separating the experience of starting Wegovy from the experience of being established on it. A number of patients describe the first few weeks as the hardest part, and then things settle into something quite manageable. That picture is consistent with what the STEP 1 clinical trial reported over 68 weeks, where the published data in the New England Journal of Medicine showed most participants completing the full treatment course.

When to get medical help without delay

Most side effects from Wegovy don't need emergency attention. But a handful do, and it's important to know what they look like before you start treatment.

Severe, persistent stomach pain that radiates to the back (with or without vomiting) can be a sign of acute pancreatitis. The MHRA issued a formal Drug Safety Update in January 2026 highlighting pancreatitis as an infrequent but serious risk associated with GLP-1 medicines including semaglutide. If this happens, stop the injection and seek urgent medical care. Don't wait to see if it passes.

Other symptoms that warrant prompt attention include: signs of a serious allergic reaction (swelling of the face, lips or throat; difficulty breathing; a widespread rash); symptoms of gallbladder problems such as sharp upper-right abdominal pain, fever or jaundice; and signs of dehydration following severe vomiting or diarrhoea, particularly if you're unable to keep fluids down. You can find a fuller breakdown of urgent warning signs on the complete Wegovy side effects page on our site.

Anyone who experiences low mood, unusual thoughts, or thoughts of self-harm while taking Wegovy should speak to a doctor or call NHS 111 promptly. These effects appear in the prescribing information, and whilst the clinical evidence is still developing, they are taken seriously. Report any suspected side effect (however minor) to the MHRA via the Yellow Card scheme; your report contributes to the ongoing safety monitoring of these medicines.

How Wegovy's side effects compare to the alternatives, and what affects your personal risk

Whether Wegovy's side effect profile is better or worse than the alternatives depends partly on what you're comparing it with. Semaglutide and tirzepatide (Mounjaro) both work on GLP-1 receptors, so their GI side-effect patterns broadly overlap. There are differences in how individuals respond, though, some people find one medicine easier to tolerate than the other, and that's not something you can predict from a chart. Our comparison of Wegovy's tolerability with other options covers this in more detail.

Individual factors that influence your side-effect experience include how quickly the dose is increased, whether you take the injection with or without food (on an empty stomach is not required for the injection, unlike the tablet form), your baseline GI health and other medicines you're taking. People who have had pancreatitis before, or who have certain gastrointestinal conditions, will need prescriber input before starting, these are reasons treatment might not be recommended, not reasons to go without clinical assessment.

There's also the question of long-term effects. The trial programme ran for up to 68 weeks, and most of what is known comes from that window. Questions about Wegovy's long-term side effects are reasonable ones to ask, and our prescribers can walk through what the current evidence shows and where gaps remain. Worth noting: face changes sometimes associated with significant weight loss on GLP-1 medicines (sometimes called "Wegovy face" in the press) are covered on the dedicated page on facial changes if that's something you've read about and want to understand properly.

What the consultation at nume covers

The side-effect question rarely has a single answer that applies to everyone. What it has is a structured clinical conversation, and that's exactly what the free consultation at nume provides. A GPhC-registered Independent Prescriber reviews your medical history, current medicines and circumstances before anything is prescribed. They won't sign off a prescription if the risks outweigh the benefits for you specifically.

If Wegovy is clinically suitable, treatment is dispatched the same day for orders placed before 12pm, arriving the next working day via DPD in plain, unmarked packaging. Aftercare is available seven days a week, so if a side effect does catch you off guard on a Saturday morning, our team is reachable. You can also browse the frequently asked questions for general information, or get in touch directly. If you're still weighing up whether Wegovy is the right fit, the full Wegovy overview and our treatment consultation page are the best places to start.