Wegovy pen malfunction: what to do if your injection doesn't work

The pen fired but the dose counter didn't reach zero

You pressed the injection button, you felt the click, but the counter stopped at (say) 0.5 rather than landing on zero. This is the scenario our prescribers hear about most often, and it is worth taking seriously. A dose counter that hasn't reached zero means the full dose was probably not delivered.

The most common cause is removing the pen from the skin before the counter completed. Wegovy's pre-filled pen requires you to hold the button down and keep the needle in the skin for at least six seconds after the click, then wait for the counter to show zero before withdrawing. Rushing that final pause is easy to do, especially on a cold morning before the kettle has boiled and your mind is elsewhere.

If the counter stopped short, do not inject again from the same pen or attempt a second device to make up the difference. Contact your pharmacy or prescriber first. They can advise whether the partial dose is clinically significant at your current titration stage and what to do with your injection schedule. The full overview of how the Wegovy pen works covers the hold-and-count technique in more detail if you want to be confident for your next dose.

For injection technique guidance written specifically for Wegovy, the NHS semaglutide medicine page links to the Patient Information Leaflet, which is the definitive source for step-by-step instructions.

The needle blocked, the pen jammed, or nothing happened at all

A fully blocked needle, a pen that won't click, or a plunger that simply won't depress, these are less common but they do occur. If you pressed the button firmly for the full count and nothing moved, the pen itself may be faulty.

First, check whether the outer needle cap was removed properly (the grey cap must come off before use; the inner needle shield detaches on skin contact). If both were removed correctly and the pen still won't activate, it is a device fault rather than a technique issue.

Do not try to unblock the needle with a pin or apply extra force to the plunger. Doing so risks an accidental needlestick, an uncontrolled dose, or damage that makes the fault harder to document when you report it. Set the pen aside, note the batch number printed on the label, and contact your pharmacy.

At nume, a replacement pen process exists specifically for documented device faults, your prescriber will review the situation before any replacement is issued. Novo Nordisk also has a customer care line for reporting device defects directly. If you believe you received a defective batch, the MHRA's Yellow Card reporting service lets you flag a product quality concern alongside any adverse reaction report.

What if the pen was dropped, overheated, or left out of the fridge too long?

Wegovy must be stored in the refrigerator between 2°C and 8°C. If your pen was accidentally left out (on a windowsill in summer, in a car glovebox, or pulled from a gym bag after a long day in the heat) the medicine may have been affected even if the pen looks fine and still fires normally.

Similarly, a pen that has frozen (perhaps placed at the back of the fridge where the temperature dips below 2°C) should not be used. Freezing damages semaglutide; a pen that has frozen and thawed may not deliver the medicine reliably. The guidance on frozen Wegovy explains this in full, including how to tell whether freezing has occurred.

For a pen left at room temperature, the Patient Information Leaflet states the permitted out-of-fridge window, the exact duration matters, and the leaflet is the authoritative source since the window can vary between pen formats. If you are unsure whether yours was out of range, treat it as compromised and call your pharmacy rather than guessing.

A pen you can't use still needs to go somewhere safe, and our page on what to do with Wegovy pens after use covers how to handle both used and unused devices correctly, including the use of a sharps container for any pen with an exposed needle.

Missing a dose because of a pen fault: when to inject next

A pen malfunction effectively means a missed dose. What you do next depends on how far through your weekly cycle the fault occurred. The Patient Information Leaflet sets out the missed-dose rules: if the problem is discovered within a specific window of your scheduled day, you may be able to inject the next available dose that same day; outside that window, skip to your next scheduled day and continue from there.

We are not going to print that window here, because it differs depending on the pen format and your current dose, and reading the wrong version could mean taking two doses too close together. Semaglutide's half-life means doubling up carries real risk of significantly amplified side effects. Check your own leaflet or call your prescriber.

If you have questions about your schedule after a fault, our support team is available seven days a week. For a broader read on what Wegovy injections involve before your next prescription, the explainer on Wegovy injections is a useful reference. And if you are still weighing up whether Wegovy is the right treatment for you, starting a free consultation with one of our GPhC-registered prescribers is the right next step.