How to inject semaglutide: a step-by-step guide for your first pen

The pen is in your hand for the first time — here is what to do

Picture the moment: the box has just arrived, DPD tracking is still open on your phone, and you are reading the leaflet at the kitchen table. The Wegovy pen looks slightly intimidating if you have never injected anything before. It is not, once you understand what each step is for.

Start by washing your hands thoroughly. Take the pen out of the fridge and let it sit at room temperature for around 15 to 30 minutes; a cold injection can sting more than it needs to. Check the pen window: the liquid should be clear or very slightly yellow and free of particles. If it looks cloudy or contains visible flecks, do not use it.

Attach a new needle by screwing it straight onto the pen tip until snug, then remove the outer and inner needle caps. Do not resheath the needle once the caps are off. For everything you need to know about attaching and handling needles safely, the guide to the semaglutide pen covers the mechanics in detail.

Choose your injection site, clean the skin with an alcohol swab and let it dry fully before you inject; damp skin increases the risk of a small sting. Press the pen flat against your skin, push the button firmly until you hear the click, then keep it pressed and count slowly to six. That six-second hold matters: it allows the full dose to be delivered before you lift the pen away. A second click during that hold is normal. Once done, pull the pen straight out, apply gentle pressure to the site with a clean tissue, and dispose of the used pen in a sharps container immediately.

Choosing where to inject semaglutide — and why rotation matters

The three approved sites are the abdomen (at least a few centimetres away from the navel), the front or outer thigh, and the outer upper arm. All three are well-established in the clinical evidence and in NHS guidance for subcutaneous injections.

Rotating sites is more than a tidying-up rule. Injecting repeatedly into the same small patch of skin can cause lipohypertrophy, a local thickening of fatty tissue that absorbs medicine unpredictably. Moving around the available areas, and varying the exact spot within each area each week, keeps absorption consistent and reduces the chance of a lump forming.

Some people find the thigh easiest when injecting alone. Others prefer the abdomen because they can see exactly what they are doing. The upper arm is perfectly valid but typically needs a second person or a mirror unless you are comfortable reaching across. A full comparison of semaglutide injection sites explains the practical differences and the evidence behind each choice, which is worth reading before you settle into a routine.

One practical note: if you are flying or have a holiday booked, room-temperature storage is permitted for a limited period specified in the Patient Information Leaflet. Check that window before you travel rather than relying on memory.

Timing, missed doses and what to do if your injection day shifts

Once-weekly dosing is one of the features that makes semaglutide workable day to day. Most people pick a day that suits their routine and stick to it. A question our prescribers hear regularly is what to do when life intervenes: say you usually inject on a Monday, but your pen arrives on a Wednesday because of a bank holiday, or you simply forgot. The answer depends on how many days have passed since the missed dose. If it is fewer than five days since you were due to inject, you can take the dose as soon as you remember, then return to your usual schedule. If five or more days have passed, skip that dose and wait for your next scheduled day. Never take two doses within four days of each other. These rules come from the Patient Information Leaflet and your prescriber's guidance, not from an approximation, so always defer to both.

Timing can also interact with oral contraceptives. For people taking tirzepatide, the pill's absorption can be affected in the first weeks of treatment, but the same concern does not have the same evidence base for semaglutide. Still, if you have any questions about how your contraception fits alongside treatment, raise them at your next clinical review. If you want a broader picture of scheduling and timing, our guide on how to use semaglutide walks through those questions in detail alongside guidance on how to take semaglutide, which covers scheduling and timing questions in broader detail.

Storage, after-injection care and knowing when to call for help

Wegovy pens are stored in the fridge between 2°C and 8°C. Keep them away from the freezer section of the fridge door, and away from ice packs; a frozen pen cannot be used. Room-temperature storage is permitted for a fixed window stated in the leaflet. The pen should be kept in its outer carton to protect it from light.

After injecting, small reactions at the site, redness, mild itching or a tiny bruise, are common and almost always settle quickly. Varying your injection sites reduces their frequency. More persistent skin reactions are worth mentioning to your prescriber.

Gastrointestinal side effects, nausea, loose stools and a general feeling of fullness, are the most commonly reported effects of semaglutide injection. They tend to be strongest shortly after starting or after a dose increase, and ease for most people within a couple of weeks. Staying hydrated and eating smaller meals helps. The side effect that warrants urgent attention is severe, persistent abdominal pain that radiates to the back, with or without vomiting, which can signal acute pancreatitis. The MHRA highlighted this in a Drug Safety Update on GLP-1 medicines published in January 2026. If you experience this, stop the injection and get medical help promptly.

If you have questions about how your treatment is going, our prescribers are available seven days a week. You can also read more about Wegovy and what it involves or, when you are ready to review your options, speak to our prescribers about the next step.