Starting Wegovy: what happens from your first injection onwards

Step 1: before you inject anything, preparation and first-day checks

A question our prescribers hear most weeks is: 'Do I need to do anything special before my first pen arrives?' The honest answer is: a little. Read the patient information leaflet that comes with your Wegovy pen before you use it. The full preparation checklist covers checking the pen hasn't been frozen, confirming the liquid is clear, and choosing your injection site, abdomen, thigh or upper arm all work; rotating between them each week reduces skin irritation. If you are on oral contraceptives, note that NHS guidance advises women starting semaglutide to discuss their contraception with their prescriber, since absorption of some medicines may be affected during early treatment. Have your prescriber's contact details to hand. Know what side effects are worth watching and which are normal. That groundwork makes the first few weeks considerably calmer.

The full run-down of things worth knowing at the outset is worth a read before your first injection day.

Step 2: your first injection and the 0.25mg starter phase

The starting dose of Wegovy is 0.25mg weekly. Think of this as an adjustment period rather than a treatment period: the purpose of this dose is to give your gut time to adapt to semaglutide before you move to doses that have a meaningful effect on appetite. You'll typically stay at 0.25mg for four weeks before your prescriber considers moving you to 0.5mg, and the schedule continues upward from there (through 1.0mg and 1.7mg) towards the 2.4mg maintenance dose. The pace is set by your prescriber based on how you're tolerating each level, not by a fixed calendar.

Nausea is the most frequently reported side effect when starting semaglutide, and it tends to peak in the first day or two after each injection. Eating smaller meals, staying well hydrated and avoiding rich or fatty foods in the hours around your injection day are the practical steps most people find useful. The NHS's patient-level guidance on semaglutide side effects and precautions sets out the full picture clearly. Most people find the nausea settles as their body adjusts, it rarely stays as disruptive as it feels in week one.

Step 3: tracking your response through the titration weeks

The weeks between your first injection and your maintenance dose are when the experience of starting on Wegovy becomes more individual. Appetite typically begins to shift noticeably somewhere in the 0.5mg to 1.0mg range, though the timing varies. Weight change in the first four weeks is often modest, this is normal, and not a sign the medicine isn't going to work. The larger reductions seen in clinical trials, including the STEP 1 trial published in the New England Journal of Medicine, were measured over 68 weeks, with average weight loss of around 15% at the 2.4mg maintenance dose. That context matters if week three feels underwhelming.

Keep a brief weekly note of how you're feeling, appetite, energy, any side effects, and your weight if you're monitoring it. This record becomes useful at your clinical review. If you reach your highest tolerated dose and weight loss is less than 5% after six months, your prescriber will discuss whether continuing makes sense, in line with NICE's recommendation for semaglutide (TA875). For context on what Wegovy typically costs as a private prescription, the Wegovy price page explains how treatment is priced and what that figure usually includes.

Step 4: when to contact your prescriber and when to get medical help

Most early side effects resolve without intervention. A few symptoms need prompt attention. Severe abdominal pain that radiates to your back (particularly if persistent and accompanied by vomiting) should be assessed urgently, as it may indicate acute pancreatitis, which the MHRA has flagged as an infrequent but serious risk with GLP-1 medicines. Signs of a serious allergic reaction (swelling of the face or throat, difficulty breathing, a rapidly spreading rash) also require emergency help. If you experience low mood or thoughts of self-harm at any point, contact your GP or call 111.

For day-to-day questions during the starting phase (missed dose queries, injection technique, managing nausea) your prescriber is the right person to ask. Our guidance on what to do when starting Wegovy covers the most common early questions, and practical tips for the first weeks may also help. If you've previously been on semaglutide and are restarting after a break, the considerations are slightly different; see our guide to restarting semaglutide for that scenario. When you're ready to speak with a clinician, start your free consultation with our prescribers, every assessment is reviewed the same day by a real clinician, not a system.