Your Wegovy pen not working? Here's what's actually going on

The biggest myth: a pen that doesn't fire is broken

Most people's first instinct when a Wegovy pen fails to inject is to assume it's defective. In practice, that's rarely the case. The pen has a pressure-sensitive mechanism that only activates when the device is held firmly and flat against the skin, held at an angle, or not pressed down hard enough, and nothing happens. That single issue accounts for a large proportion of calls our clinical team fields about pens that seem not to work.

The second most common cause is cold medicine. If your pen has come straight from the back of the fridge (particularly if it's been sitting against the cooling element) the liquid inside can be too cold to flow easily. Taking it out and holding it in your hands for 15 to 30 minutes before injecting makes a meaningful difference. Think of it the same way you'd warm a cold butter dish: a little patience changes everything.

A needle that wasn't attached securely, or one that has been left on from a previous injection, can also block delivery. The needle should be fitted fresh each time, just before you inject, and removed straight after. If you need a reliable supply, a pack of compatible needles is available from our pharmacy.

Check the NHS semaglutide guidance for a plain-English summary of how the pen should be used alongside the full Patient Information Leaflet that comes in the box.

What to check when my Wegovy pen is not injecting any liquid

Work through this short sequence before deciding the pen is faulty. First, confirm the pen has been primed: a small drop of liquid at the needle tip confirms it's ready. If no drop appears after the priming step, the needle may be blocked, fit a fresh one and try again. Second, check the dose window: if it still reads a number after you've pressed the button, the full dose hasn't been delivered.

Next, think about where you're injecting. The abdomen, outer thigh and upper arm are the licensed sites. Pressing into muscle rather than a soft pinch of skin can affect delivery and comfort. Our clinical team has put together more detail on where exactly to place the injection if you're unsure.

If the pen clicks but you see or feel nothing, read through the troubleshooting section of the Patient Information Leaflet specifically. A pen that clicks without delivering medicine is a different presentation from one that is completely stiff, the leaflet distinguishes between them. You can also read about what it means when the pen doesn't click at all, which points to a different set of causes.

If none of these steps resolve it, call the manufacturer's helpline number printed on the packaging, and contact your prescriber to discuss whether the dose was likely delivered or needs repeating. Never try to re-inject from the same cartridge with a different device.

Storage problems are more common than people realise

Wegovy pens must be refrigerated between 2°C and 8°C. Beyond that, the Patient Information Leaflet specifies a limited window during which a pen can be kept at room temperature, always defer to the leaflet for the exact duration, because it differs from what people assume and getting it wrong risks using medicine that's no longer effective.

Frozen medicine is a clear problem: if a pen has been stored in the freezer compartment, left overnight in a car in winter, or pushed against the freezer wall of a badly calibrated fridge, it should not be used. Freezing can degrade the semaglutide even once thawed. Similarly, pens left in a warm gym bag, left on a windowsill, or taken through airport security in hold luggage can be exposed to temperatures that compromise them.

Practical habit: keep your current pen on a middle shelf in the fridge door rather than at the back, and bring it to room temperature just before your weekly injection. Pens waiting for future weeks stay refrigerated until needed.

If you're unsure whether a pen has been stored correctly, don't use it, contact your prescriber. Using degraded medicine means missing a dose effectively, which matters because how soon after injection Wegovy starts working depends on each dose being delivered properly, and for how long Wegovy takes to show results.

When to contact a prescriber, and what happens next

Contact your prescriber if: the pen appears to have partially injected but you're unsure how much was delivered; the pen is damaged or leaking; you've been unable to inject after trying the steps above; or you experience unusual pain or swelling at the injection site that doesn't settle. Our clinical team is available seven days a week for exactly these situations, that's part of what aftercare means in practice.

If a dose has been fully missed because the pen failed, your prescriber can advise whether to inject as soon as possible (if the next scheduled dose is still several days away) or to skip and resume the normal schedule. Do not double-dose. The Patient Information Leaflet covers the timing rules clearly; the decision on what to do in your specific situation sits with your prescriber.

It's also worth knowing that a pen problem is separate from the medicine stopping working over time, that's a different question entirely, covered in our guide to what happens when Wegovy stops working. If you have questions about your treatment or are thinking about starting, you can begin a free consultation with one of our GPhC-registered prescribers at any time.