Efeito Colateral Wegovy: What Side Effects Should You Know About?

Which side effects do most people on Wegovy actually notice?

The majority of people taking semaglutide for weight management experience at least one gastrointestinal symptom at some point. Nausea tops the list. After that come vomiting, loose stools or constipation, acid reflux, burping and a feeling of fullness that arrives quickly during meals. Fatigue and headaches appear less often but are still documented in trial populations. Injection-site reactions (mild redness or tenderness where the pen was used) are occasional and usually brief.

Timing matters here. Symptoms are most intense in the first one to two weeks after starting treatment or stepping up to a higher dose. The slow titration schedule (beginning at 0.25 mg and moving through doses roughly every four weeks) exists precisely to give the body time to adapt. For the majority of patients, the discomfort is noticeable but manageable, and it recedes. A useful one-minute check: before each meal during your first weeks on treatment, rate your nausea on a simple 1-to-5 scale. Tracking it takes seconds, and a clear downward trend over a fortnight tells you the adjustment is on course. If the score stays high or climbs, that is worth raising with your prescriber rather than waiting.

The structured titration is covered in more detail on our Wegovy ramp-up guide, which explains what each dose step involves and why the schedule is set the way it is.

Are there Wegovy side effects that need urgent medical attention?

Yes — and being clear about this is more useful than a blanket reassurance. On 29 January 2026, the MHRA issued a Drug Safety Update for GLP-1 receptor agonists, including semaglutide, drawing specific attention to acute pancreatitis. The signal was there before that date, but the update formalized the advice: if you develop severe or persistent stomach pain that spreads toward your back, with or without vomiting, seek urgent medical help. That pattern of pain is not typical of ordinary GI upset and should not be waited out.

Other situations that warrant prompt contact with a healthcare professional include signs of gallbladder problems (sudden upper-right abdominal pain, fever, jaundice), symptoms consistent with serious dehydration from prolonged vomiting or diarrhoea (dizziness on standing, very dark urine, inability to keep fluids down), or any signs of a significant allergic reaction such as facial swelling or breathing difficulty. A change in mood, or thoughts of self-harm, should also be taken seriously and reported without delay.

The MHRA Yellow Card scheme allows patients to report side effects directly, and doing so contributes to the ongoing safety monitoring of these medicines. Our detailed Wegovy side effects page goes deeper into each category for readers who want the full clinical picture.

Do Wegovy's side effects affect how and what you eat?

Appetite changes are the point of the medicine, but they interact with side effects in practical ways. When nausea is present, certain foods reliably make it worse: high-fat meals slow gastric emptying further, intensifying the fullness and queasiness; very sweet or heavily spiced foods can have a similar effect for some people. Smaller portions spread across the day, with an emphasis on protein and fibre, tend to reduce symptom severity during the adjustment phase.

Some patients find that specific cravings shift unexpectedly during treatment. Chocolate is a common one, both reduced craving and, for some, an intensified one early on. Our page on craving chocolate on Wegovy looks at why that happens and whether it tends to resolve. Separately, reduced appetite can make it harder to meet protein targets; this is worth discussing with a prescriber or dietitian because muscle preservation matters alongside fat loss, a topic explored further in our piece on Wegovy and visceral fat.

Hydration deserves a mention too. Nausea suppresses thirst signals for some people, and mild dehydration amplifies headaches and fatigue. Plain water throughout the day, in small amounts if large volumes feel uncomfortable, is consistently useful advice during the early dose period.

How does Wegovy compare to other semaglutide formulations for side effects?

Semaglutide is the active ingredient in more than one licensed medicine, which causes some understandable confusion. Ozempic contains the same molecule but is licensed for type 2 diabetes, the weight-management licence belongs to Wegovy. The side-effect profile across semaglutide formulations is broadly similar because the mechanism is the same, but there are presentation differences worth knowing about.

The recently approved oral semaglutide tablet, also branded Wegovy, carries its own GI side-effect profile. Trial data showed gastrointestinal events in around 74% of participants taking the tablet versus 42% on placebo, higher rates than many injectable studies, though most events were mild-to-moderate and transient. The tablet's absorption mechanism requires it to be taken on an empty stomach with a small amount of plain water, with a 30-minute gap before food or other medicines. Missing that window affects how much semaglutide reaches the bloodstream and may worsen tolerability. More on how semaglutide works across its different forms is on our semaglutide overview page.

For anyone weighing up whether Wegovy is the right option given its side-effect profile, or wondering how costs factor into the decision, our Wegovy cost guide sets out what private treatment actually includes beyond the headline price. If you'd like a prescriber to review your specific situation, you can speak to our prescribers through a free consultation, it's reviewed the same day by a GPhC-registered clinician, not software.