How to prime your Wegovy pen with a new needle

You've attached the needle, now what?

Picture the scene: you've taken your Wegovy pen out of the fridge, let it sit for roughly 30 minutes to reach room temperature, and you're holding a new needle ready to screw on. It's easy to assume the pen is ready to go the moment the needle clicks into place. It isn't, and that assumption is probably the most common small mistake people make with pre-filled injection pens. The needle hub (the tiny plastic channel connecting the cartridge to the needle tip) contains a pocket of air. If you skip the flow check and inject straight away, that air goes in first rather than your medicine. The dose you receive may be incomplete.

Before attaching the needle, check the liquid in the pen's cartridge window: Wegovy should be clear and colourless. If it looks cloudy, discoloured or has visible particles, do not use that pen, contact your prescriber and the manufacturer's helpline. Once you're satisfied the liquid is fine, peel the outer paper tab from a fresh needle and screw it straight onto the pen's threaded tip, turning clockwise until it is snug but not overtightened. Remove only the outer needle cap for now and keep the inner cap in place until you are ready to inject.

At this point you have an attached, capped needle and a pen that is not yet ready to use. The flow check is what bridges those two states. It is a brief, deliberate step, not optional, not only for new pens, not something you grow out of once you're confident with the injection routine.

Turning the selector to the flow-check symbol and pressing the button

Turn the dose-selector dial until the flow-check symbol lines up with the pointer. Your patient information leaflet shows what this symbol looks like: it is typically a small rectangle or arrow icon, distinct from any dose number. This matters because if you accidentally prime with a dose dialled in, you waste medicine that was meant to be injected. Dial to the flow symbol specifically.

Now hold the pen with the needle pointing straight upward. Remove the inner needle cap and set it aside. Press the dose button fully and hold it down for a few seconds. Watch the needle tip. You are looking for a single, small drop of clear liquid to appear. That drop tells you three things: the needle is attached properly, the cartridge is primed through to the tip, and the dose-delivery mechanism is working. One drop is enough. You do not need a stream of liquid; you are not trying to expel a meaningful amount of medicine.

The semaglutide NHS medicines guide confirms that a flow check should be performed before each injection when you are using a new needle, and this aligns with Novo Nordisk's own pen instructions. If no drop appears, check that the needle is firmly attached, point the pen upward again and repeat, up to six attempts are acceptable before you should treat the pen as potentially faulty and contact your prescriber or the manufacturer. Curious about what the process looks like if you're switching from one pen technique to another? The full Wegovy pen priming guide covers the broader picture.

After the flow check: setting your dose and injecting

Once you've seen the drop, the pen is primed. Do not re-prime, doing so a second time wastes medicine. Dial the selector to your prescribed dose now. That dose was set by your prescriber based on where you are in the titration schedule, not by the pen itself, so only change the number if your prescriber has told you to. If you're unsure which dose you should be on, your prescription paperwork and patient leaflet will confirm it; don't guess from a number that seems right.

Clean the injection site (abdomen, outer thigh or upper arm are all suitable) with a clean swab, and allow it to dry for a few seconds. Insert the needle at a 90-degree angle in a smooth, confident motion, then press the dose button fully and hold it for ten seconds before withdrawing. The ten-second hold is not about pain tolerance; it ensures the full dose has been delivered before the needle pulls back. After withdrawal, check that the dose window shows zero.

Place the used pen (with the needle still attached, for safety during disposal) carefully into a sharps container if you are recapping is impractical, or re-cap using the outer cap only (never the inner), then remove the needle and dispose of it in a sharps bin. Never leave uncapped needles loose. For a broader look at what to expect from Wegovy, including how it works and eligibility, the Wegovy treatment page is a good next read.

Common questions the flow check raises

One question that comes up regularly: does priming count as part of the dose? The short answer is no. The flow-check step is designed to move just enough liquid through the needle to displace air, it does not subtract a meaningful quantity from your dose. The pen is engineered to account for this. So the drop you see at the needle tip does not mean you've wasted your medicine; it means the pen is working correctly.

Another point worth clearing up: some people wonder whether they can reuse a needle and skip priming because the needle is already attached from last week's injection. Our guide on the Wegovy needle explains why needles should never be reused. Even a microscopic bend in the tip that you cannot see affects where and how the medicine is deposited, and a needle left on the pen between doses can allow air to enter the cartridge, which is precisely the problem priming is designed to solve. Attach a fresh needle every time, prime every time.

If you find yourself uncertain about any part of the process, the guidance on how to attach a Wegovy needle correctly covers that first step in detail. Questions about whether you need to prime at all (perhaps because you've read conflicting advice) are addressed in our guide on whether priming is always necessary. If you need to carry out the process without a needle to hand, our page on how to prime a Wegovy pen without a needle walks through that scenario in detail. And if you want to compare how the injection-pen process differs from other weight-loss treatments, the weight-loss treatment overview gives useful context.

If your prescriber or the support team at a registered service has given you specific instructions that differ from the general steps above, follow theirs, prescribers tailor guidance to individual circumstances. Speak to our prescribers at any point if something about your injection routine feels uncertain, and they'll give you a clear answer specific to your pen and your dose.