Your first day on Wegovy: a step-by-step guide to what happens

Step 1: Before you inject, the checks that take under a minute

Pull your Wegovy pen from the fridge and let it sit at room temperature for around 15 to 30 minutes. A cold injection is not dangerous, but it is more comfortable when the liquid has warmed slightly. While you wait, glance at the liquid through the pen window: it should be clear or faintly yellow, with no floating particles. If it looks cloudy or discoloured, do not use that pen, contact your prescriber instead. That quick visual check is a habit worth building from day one.

Choose your injection site: abdomen (at least five centimetres from the navel), outer thigh, or upper arm. Clean the area with an alcohol swab and let it dry. Remove the pen cap, press the pen firmly against your skin at 90 degrees, and press the button until you hear a click. Hold it there for ten seconds before removing. The full Wegovy overview on our treatment page covers injection technique in more detail if you want to review it before you begin.

Step 2: The first few hours, what you are likely to feel

For many people, the first few hours after the 0.25 mg dose pass without incident. Some notice mild nausea, usually starting one to three hours post-injection and lasting a few hours; others feel nothing at all. Fatigue, a slight headache, or a vague feeling of fullness are also reported, but these are far from universal at the starter dose.

The mechanism behind any nausea is well understood: semaglutide activates GLP-1 receptors in the gut and brain, slowing gastric emptying and influencing signals in the area of the brain that controls nausea. That is, in a sense, the medicine working, but the 0.25 mg dose is calibrated precisely to keep that response modest. If you do feel queasy, eating small, plain meals, staying upright after eating, and drinking water steadily through the day tends to help. Ginger is a practical option too. Our dedicated day-one guide includes practical meal ideas for those first hours.

One thing the first injection will not do is noticeably reduce your hunger. Appetite suppression builds gradually over the weeks of treatment, not within a single day.

Step 3: The rest of day one, monitoring and simple record-keeping

You do not need to rearrange your day around the injection. Most people carry on normally. What is worth doing is taking a note of anything you feel (and when) so that you and your prescriber have something concrete to work from when your next clinical review comes around. A few lines in your phone's notes app is enough.

Keep an eye on injection-site reactions: minor redness or swelling at the site is common and short-lived. If you notice a larger raised lump that does not settle within a day, let your clinical team know.

Seek medical attention promptly if you experience severe or persistent stomach pain that radiates to your back, with or without vomiting. That pattern can indicate acute pancreatitis, which the MHRA flagged in a January 2026 Drug Safety Update for GLP-1 medicines. It is uncommon, particularly at the starter dose, but worth knowing about. If something feels seriously wrong, dial 111 or attend A&E, do not wait to contact your prescriber.

Step 4: Setting up the routine before day two arrives

By the end of day one, the most useful thing you can do is decide on your weekly injection day and put a recurring reminder in your calendar. Consistency matters: semaglutide's half-life means that injecting on the same day each week keeps blood levels stable. You can shift the day by a day or two if you need to (your Patient Information Leaflet covers the details) but picking a day that suits your routine from the start makes it easier to stick to.

You will stay on 0.25 mg for four weeks before moving to the next dose level. What that first month looks like in practice is covered in our guide to the first month on Wegovy. Meanwhile, our first week on Wegovy piece picks up exactly where this page leaves off, tracking how side effects and appetite signals tend to evolve across those seven days, and if you want to look further ahead, our guide to day two on Wegovy covers what to expect when you wake up the morning after your first injection.

A note on costs, since it comes up: if you are trying to understand what private treatment involves financially, our Wegovy pricing guide explains what a legitimate private prescription typically includes and why the headline number alone rarely tells the full story.

Wegovy is a prescription-only medicine. Before your first injection, a clinical consultation with a GPhC-registered prescriber will have confirmed it is right for you, that assessment matters at every stage, not just at the start. If questions come up as treatment progresses, our prescribers are reachable seven days a week.