What happens when you take Wegovy: a step-by-step guide

Step 1, the first injection and the days that follow

The pen arrives in a plain, unbranded box via DPD; you will get a tracking notification so you are not waiting in for a mystery delivery. Each pre-filled Wegovy pen delivers a subcutaneous injection once a week, into the abdomen, thigh or upper arm.

After that first dose, semaglutide begins binding to GLP-1 receptors in the hypothalamus (the part of the brain that regulates appetite) and in the gut wall. Hunger signals quieten. Food passes through the stomach more slowly, which means a smaller meal creates more fullness than it did before. These effects are not dramatic on day one; the 0.25 mg starting dose is a settling-in dose, and most people describe the early change as a gentle reduction in appetite rather than anything abrupt.

Nausea is the most frequently reported experience in the opening weeks. It tends to arrive in the hours after an injection and ease before the next dose. Eating smaller portions, keeping meals low in fat, and staying well hydrated all help. The nume FAQs, sorry, the nume FAQs address common early questions, including what to do if you feel unwell after a dose.

The NHS medicines guidance on semaglutide notes that GI effects are most noticeable when treatment starts or a dose increases, and generally improve as the body adapts.

Step 2, the titration period (weeks 4 to 16 or so)

Your prescriber advances the dose in roughly four-week steps: 0.25 mg, then 0.5 mg, 1.0 mg, 1.7 mg, and finally 2.4 mg. Each increase can bring a brief return of mild nausea or digestive changes as your system adjusts to the new level. This is expected. It does not mean the medicine is not working, and it usually passes within a week or two of the new dose.

Appetite continues to fall across this phase. People typically find their natural portion sizes shrink without conscious effort, meals that once felt modest now feel adequate, and the mental churn around food tends to lessen. Weight changes during titration are real but modest compared with what comes later; the therapeutic effect builds as the dose rises.

Understanding what happens if a dose is accidentally doubled is worth knowing too. The semaglutide overdose page explains the signs and when to seek help. Similarly, anyone curious about the effects of taking too much Wegovy specifically will find a detailed answer there. Always store the pen in the fridge between 2 °C and 8 °C; the Patient Information Leaflet (available on the electronic Medicines Compendium) gives the exact window for room-temperature storage before use.

Step 3 (maintenance and what steady-state looks like

At 2.4 mg maintenance) or 7.2 mg if your prescriber moves you to the higher-dose pen approved by the MHRA in April 2026, the medicine is doing its full job. The STEP 1 trial published in the New England Journal of Medicine found an average weight reduction of around 15% over 68 weeks at the 2.4 mg dose, in adults with obesity alongside lifestyle changes. That is a population average. Some people see more, some less; biology, starting weight, diet quality and activity all play a part.

Practically, steady state means hunger remains lower week to week, energy levels often improve as weight comes off, and the GI side effects that characterised the titration phase are largely gone for most people. Injection day becomes routine. A supply of alcohol swabs for site preparation is a small but useful addition to your routine, and rotating injection sites prevents localised skin irritation.

This is also where regular clinical re-review matters. Every repeat order through nume is assessed by a prescriber before dispatch, not automatically renewed. If weight loss has stalled, if side effects persist, or if circumstances have changed, those conversations happen at that point. Our clinical team oversees every stage of treatment.

Side effects to know and when to get medical help

The most common effects are gastrointestinal: nausea, vomiting, diarrhoea, constipation, burping, reflux. These are well-documented in the NHS patient information for semaglutide and are generally mild to moderate. Headache, fatigue and dizziness appear less commonly, usually early in treatment.

Seek urgent medical attention for severe, persistent stomach pain that spreads to your back, with or without vomiting. This can indicate acute pancreatitis, which the MHRA highlighted in a Drug Safety Update in January 2026 as an infrequent but serious risk with GLP-1 medicines. Gallbladder problems are also reported; worsening upper-right abdominal pain warrants a call to your GP or 111 without delay.

Signs of a serious allergic reaction (swelling of the face, throat or tongue, difficulty breathing, severe rash) require emergency services. Report any suspected side effects, including those not listed in the leaflet, through the MHRA Yellow Card scheme. Patients and carers can report directly; you do not need a clinician to do it for you.

Women who take an oral contraceptive pill should know that tirzepatide (a different medicine) requires an additional non-oral contraceptive method during dose increases; current NHS guidance does not identify the same pill-absorption concern for semaglutide, though discussing contraception with your prescriber before starting any GLP-1 medicine is good practice. Wegovy is not recommended during pregnancy, breastfeeding or when actively trying to conceive.

If you are wondering what happens over the longer term, the effects of stopping Wegovy are covered separately, and you can also read about what happens when you stop taking Wegovy or explore what getting off Wegovy involves in practice if you are thinking ahead to that stage. For anyone considering private treatment, the consultation page is the place to start, a GPhC-registered prescriber, not an algorithm, reviews your information the same day.