Using the Wegovy Flex Pen: what to expect before your first injection

What does the Wegovy flex pen look like, and how is it different from other semaglutide devices?

The Wegovy pen is a slim, pre-filled autoinjector made by Novo Nordisk. It holds enough semaglutide solution for one weekly injection and is supplied as a single-use device, once the dose is delivered, the pen is finished. There is no reservoir to refill and no cartridge to swap.

A common misconception is that the pen works like an insulin pen where you dial up whatever dose you need. It does not. The strength is fixed at manufacture: a 0.25 mg pen delivers 0.25 mg, a 1.7 mg pen delivers 1.7 mg, and so on through the titration schedule. Your prescriber determines which strength is right for where you are in treatment; the pen itself has nothing to adjust.

The device has a dose counter window so you can confirm the pen is full before use, a green injection button, and a needle cap. When you press the button you'll hear two clicks, the first signals the injection has started, the second confirms the full dose has been delivered. Keeping the pen pressed against your skin until the second click is the part most people rush initially; a slow count of ten after the first click is a useful habit. The Wegovy pen overview covers the available strengths and how pens are supplied at each stage of treatment.

Which injection sites work best with the flex pen, and how should you rotate them?

Semaglutide is injected subcutaneously (into the fatty layer just beneath the skin) at one of three sites: the abdomen (at least 5 cm from the navel), the front outer thigh, or the upper outer arm. All three are effective. The abdomen tends to be easiest to reach independently; the thigh is a practical second choice when the abdomen is uncomfortable. Upper arm injections are straightforward if someone else can assist, though they are perfectly possible alone.

Rotating sites matters more than people realise. Injecting repeatedly into the same small patch of skin can cause lipohypertrophy, a lumpiness under the skin that actually slows absorption and makes the medicine less reliable. A simple approach is to divide each site into a grid of small areas and move one square along each week, cycling through all three sites over time.

The volume per injection is small (around 0.5 ml at most doses) so discomfort is usually brief. Letting the pen come to room temperature for 30 minutes before injecting, rather than using it straight from the fridge, often reduces the brief sting on injection. If you are moving through the titration schedule and want to understand what to expect at a specific point, the Wegovy 1 pen page covers that dose in detail. The 1 ml pen format details explain any volume differences across the dose range if you want to compare.

What do you need alongside the pen, and how is it stored between doses?

The pen does not come with needles. You'll need a compatible pen needle for each injection, 4 mm or 5 mm needles are standard for subcutaneous use, but confirm with your prescriber which length suits your injection sites. Attaching a fresh needle every time, rather than reusing the same one, keeps injections comfortable and reduces infection risk. Our pen needles are compatible with the Wegovy device.

Cleaning the skin before injecting with an alcohol swab and allowing it to dry fully before pressing the pen against it is good practice, particularly in warmer months.

Storage: Wegovy pens live in the fridge between 2°C and 8°C. Once a pen has been used or has been kept at room temperature, the exact window during which it remains usable is set out in the Patient Information Leaflet, the NHS semaglutide guidance recommends checking there rather than relying on secondhand summaries, because the window varies by dose. Never freeze the pen. Keep it away from direct light and heat.

Used pens and needles are clinical waste. A sharps container is the correct way to dispose of them; local councils and many GP surgeries accept sealed sharps bins for collection. Putting needles loose in household recycling is unsafe and illegal.

Are there side effects specific to how the injection is given, separate from semaglutide's general profile?

The systemic side effects of semaglutide (nausea, loose stools, constipation, indigestion) are well described and covered in the Wegovy treatment guide. The injection itself can produce a separate, localised reaction: redness, mild swelling, or a brief itchy patch at the injection site. These are common and almost always short-lived, resolving within hours.

Persistent nodules, bruising, or pain that does not settle within a day or two suggest the technique may need adjusting, usually the injection angle (aim for 90 degrees, or 45 degrees if you have very little subcutaneous tissue) or the rotation pattern. If a reaction keeps recurring in the same spot, that spot has probably been used too often.

The NHS's patient information for semaglutide lists the full side-effect profile and the signs that warrant a call to your care team. For anything beyond a mild local reaction (severe stomach pain, signs of an allergic response, or symptoms that feel disproportionate) contact a prescriber promptly rather than waiting for your next scheduled review.

If you are curious about how the Wegovy device compares to other pen formats in the range, the FlexTouch pen page covers that distinction in detail. Questions about whether Wegovy is right for you clinically, or about starting the process, are best answered through a consultation, you can check your eligibility with our prescribers at any point.