Wegovy side effects in week 2: what's normal, what to watch

You've just had your second injection — here's what your body is doing

Imagine it's a Tuesday morning, a week after your first Wegovy pen. You injected last night and you've woken up feeling a little queasy, not hungry at all, and slightly foggy. This is genuinely one of the most reported week-two experiences, and it has a straightforward explanation.

Semaglutide works on GLP-1 receptors in the gut and brain, slowing how quickly food leaves your stomach and reducing the appetite signals your brain receives. During the first week, your body met this mechanism for the first time. In week two it meets it again, at the same 0.25mg starter dose, but now without the novelty buffer. If you want a clear picture of what to expect in the first week of Wegovy before comparing it to where you are now, that page is a useful reference point as the medicine's effects accumulate.

Nausea is the most commonly reported effect. It usually peaks in the hours following an injection and eases over the next two or three days. Eating smaller portions, avoiding rich or fatty meals, and staying hydrated all help. The NHS semaglutide medicines page confirms this GI-led pattern and gives practical guidance on managing it. Fatigue and mild headaches also appear in some people during week two, likely linked to reduced calorie intake as appetite falls. Neither is a reason to stop without speaking to your prescriber first.

The side effects worth monitoring closely in week 2

Most week-two symptoms are uncomfortable rather than dangerous. A few, though, deserve your attention rather than quiet patience.

Gallbladder symptoms (pain in the upper right abdomen, particularly after eating) are worth flagging to a clinician. Rapid weight loss itself (not just GLP-1 medicines) can increase gallstone risk, and semaglutide has been associated with gallbladder-related events in trials. If the pain is sharp and persistent, don't wait for your next scheduled check-in.

Dehydration is a quieter risk. If nausea or diarrhoea is frequent enough to reduce what you're drinking, you can become dehydrated faster than you'd expect, especially if you're also eating less. Signs to take seriously: dizziness on standing, very dark urine, or feeling genuinely faint.

The most urgent signal is severe abdominal pain that doesn't ease and spreads towards the back, with or without vomiting. This pattern can indicate acute pancreatitis, which is rare but serious. In January 2026 the MHRA issued a specific Drug Safety Update for GLP-1 medicines covering this risk. If that pain describes what you're feeling, seek medical help the same day, don't wait to see if it passes.

Injection-site reactions (redness, itching, a small lump) are common and usually resolve within a day or two. Rotating the injection site each week helps keep them minor.

When to call someone, and who that someone should be

The scenarios that need prompt medical attention are: severe stomach pain reaching the back; signs of a serious allergic reaction (swelling of the face or throat, difficulty breathing, rapid heartbeat); persistent vomiting preventing you from keeping fluids down; or any sudden changes in vision if you have a history of diabetic retinopathy.

For anything that concerns you outside those urgent signs, your prescriber is the right first call. At nume, aftercare runs seven days a week through our support team, so a question about week-two nausea doesn't have to wait until Monday, though if your injection happens to fall on a Friday, the weekend team can still help. If your concern is more general, our FAQs cover some of the most common week-two questions.

You can also report any suspected side effect directly through the MHRA Yellow Card scheme. It's designed for exactly this: real-world monitoring of medicines, and patients reporting their own experiences are genuinely useful to regulators.

What usually happens after week 2, and whether this gets easier

For most people, it does. The 0.25mg starting dose is held for four weeks precisely to give your system time to adjust before any increase. Our page on week 4 Wegovy side effects explains what to expect once you reach that next milestone. Our page on week 3 Wegovy side effects covers what that transition typically looks like.

Appetite suppression, which can feel disorientating at first, usually becomes easier to work with as the weeks go on. Eating enough protein, drinking water consistently, and not skipping meals entirely are the things our prescribers find make the biggest difference to tolerability in these early weeks. It's worth reading the broader picture of the Wegovy side-effect profile across the full course, so week two doesn't feel like a preview of what the next year holds.

If you're still deciding whether Wegovy is the right option for you, comparing tolerability profiles is a reasonable part of that decision, our page on Mounjaro versus Wegovy side effects sets out the differences factually. Our prescribers cover all of this as part of the initial consultation, including how your own medical history shapes what to expect. To talk through your suitability, check your eligibility with a free consultation.