Semaglutide needles and how the Wegovy injection works

Step 1, Taking the pen out of the fridge and getting ready

Wegovy pens are stored in the fridge at 2–8°C. Before you inject, allow the pen to reach room temperature for a few minutes, cold medicine can make the injection more uncomfortable. Check the pen window: the liquid should be clear and colourless, with no visible particles. If it looks cloudy or discoloured, do not use it; contact your prescriber or pharmacy.

The NHS medicines page for semaglutide confirms the storage requirements and lists what to check visually before each dose. A question our prescribers hear most weeks is whether the pen can be left out of the fridge permanently, the answer is no. There is a limited room-temperature window for each pen, and the exact duration is set out in the Patient Information Leaflet, so refer there rather than relying on a general figure you may have read elsewhere.

Remove the pen cap. You will see the needle tip is already sealed inside the pen, there is nothing to screw on or swap out. That design is one of the practical differences between Wegovy and older insulin pens, which did require a separate needle for every use. If you are curious about whether Wegovy needs separate needles, the short answer is no, and our page on Wegovy needles explains exactly how the built-in tip works and what that means for your injection routine.

Step 2, Choosing your injection site and cleaning the skin

The three approved sites for a semaglutide injection are the abdomen (stomach area, at least 5 cm from the navel), the front of the thigh, or the outer upper arm. Each site is equally effective; the choice is mostly about personal comfort and which you can reach easily.

Rotate the injection site each week. Using the same spot repeatedly can cause the skin to thicken or develop lumps (a condition called lipohypertrophy) which slows absorption of the medicine. A simple way to track rotation is to note the site in your phone each time. Clean the skin with an alcohol swab and let it dry fully before inserting the pen; injecting through wet skin can sting. For detail on the needle length and how far it reaches into the tissue, this page on semaglutide needle size covers the specifics.

Never inject into skin that is bruised, tender, scarred or affected by a rash. If you develop redness or soreness that does not settle within a day or two at an injection site, flag it with your prescriber at your next check-in, or sooner if it is spreading.

Step 3 (Delivering the dose and what to do immediately after

Press the pen firmly against the chosen site and hold it there) the needle deploys automatically and the dose is delivered when you press the injection button. Keep the pen against the skin for the full count indicated in your leaflet (typically around 6 seconds) to ensure the complete dose is given before you lift the pen away. A click or a window change on the pen confirms the dose has been delivered.

After you lift the pen away, the needle retracts back into the tip. Do not try to re-use a pen, each Wegovy pen is single-use by design. If you are managing pins and needles or tingling sensations after starting semaglutide, that is a separate topic worth exploring, as it is occasionally reported during dose changes.

Dispose of the used pen immediately in a purpose-built sharps bin. A 1-litre sharps container is the standard size for home use and keeps used pens safely contained until your local pharmacy or council collection service can take them. Placing used pens in a household bin is unsafe and, in most areas, not permitted.

Managing the practicalities week to week

Wegovy is a once-weekly injection, so most people settle into a routine quickly: same day each week, same general time if possible, pen already noted in the calendar. If you miss a dose, the guidance in your Patient Information Leaflet sets out exactly what to do depending on how many days have passed, this is not something to guess at, and your prescriber or the leaflet is the right source.

Side effects after injection are mostly gastrointestinal in nature: nausea, loose stools and stomach discomfort are common, particularly after starting or moving up a dose. They tend to ease as the body adjusts. On very rare occasions, a severe and persistent stomach pain that radiates to the back could indicate pancreatitis, which needs urgent medical attention, the MHRA issued a formal safety communication on this in January 2026. Report any unexpected or concerning reaction through the MHRA Yellow Card scheme.

For a broader overview of the medicine itself, the Wegovy treatment page covers how semaglutide works, what the clinical evidence shows and how private access through a regulated pharmacy compares with NHS routes. If you are at the stage of thinking about whether this treatment is right for you, you may also find it helpful to read about how the fat loss pen semaglutide works before starting a free consultation, where a GPhC-registered prescriber will review your answers the same day.