Your Wegovy pen isn't working — here's what to do about a defective pen

The pen looked fine in the fridge, so why didn't it work?

Picture this: you've taken the pen from the fridge door, let it sit at room temperature as the leaflet says, swabbed the site, attached the needle, dialled up, pressed the button, and nothing happened. Or something happened but the dose window didn't move. It's an unsettling moment, and the instinct to try again is understandable.

Don't. A pen that has misfired or failed to advance the dose counter should be capped immediately and set aside. Attempting a second injection risks a double dose if the first actually did deliver, or needle-stick injury if you dismantle it to investigate. Wegovy pens are single-patient, pre-filled devices; they are not designed to be taken apart.

Failures can happen for several reasons: the pen was not stored correctly (it must be refrigerated at 2–8°C until first use, then used within a limited room-temperature window specified in your Patient Information Leaflet), the needle was not attached firmly, or there is a genuine manufacturing defect. The cause matters less at this stage than the response. Cap the pen, note the batch number printed on the label, and move on to the steps below. You can find more on correct injection technique, including which body areas give the most consistent results, on our guide to Wegovy injection sites.

How to report a faulty Wegovy pen, and why it genuinely matters

Reporting a defective pen is not bureaucracy for its own sake. Wegovy (semaglutide) carries a Black Triangle (▼) designation from the MHRA, meaning it is subject to additional post-market monitoring. Every reported fault contributes to that picture. The MHRA's Yellow Card scheme accepts reports from patients directly, you do not need to go through a doctor or pharmacy first, though telling your prescriber too is important.

When you report, note: the batch number, the expiry date, where you stored the pen, how long it had been out of the fridge before use, and exactly what happened when you tried to inject. Novo Nordisk also has a product quality complaint line; the number is in your patient information leaflet. Keep the pen (faulty or otherwise) in a sharps container with the needle removed (if you attached one) until you receive disposal instructions, and if you are unsure whether a needle issue rather than the pen body is to blame, our guide to Wegovy needle replacement explains when a needle swap resolves the problem. Do not put it in your household recycling.

Your pharmacy should also hear from you as soon as possible. For patients prescribed through a private clinic or pharmacy, this is the first practical step toward getting a replacement arranged, but that replacement will need clinical sign-off, not just a customer service call.

Getting a replacement: what the clinical review involves

A defective pen does not entitle you to an automatic replacement in the same way a faulty kettle might. Wegovy is a prescription-only medicine, which means any new supply requires a prescriber to assess whether it is appropriate to reissue. In practice, for a straightforward device failure mid-course, most prescribers will agree quickly, but the step cannot be skipped.

At nume, every prescription, including replacements following reported device failures, is reviewed by a GPhC-registered Independent Prescriber. A real clinician reads the case; it does not go through an automated queue. If the fault is confirmed and your treatment is otherwise progressing as expected, the aim is to have a replacement dispatched the same day, with free next-working-day delivery via DPD. Questions about what your prescription covers and the cost of a replacement pen are best answered through our Wegovy pricing page or by contacting the team directly.

If you are mid-titration and a defective pen means you have missed an injection entirely, do not simply double up when the replacement arrives. Your prescriber will advise on the right approach, this is one of those situations where the answer depends on how long the gap has been, which the Patient Information Leaflet addresses under missed doses, and which our prescribers can speak to directly. For a full picture of what happens when a device stops working part-way through a course, our guide to Wegovy pen malfunction replacement covers the process in detail.

Staying on track while you wait

Missing one dose of Wegovy is not a catastrophe. The medicine's long half-life means a single delayed injection rarely undoes progress. The greater risk is anxiety leading to improvised decisions: trying to use the faulty pen again, borrowing a pen, or sourcing a replacement through an unverified channel.

That last point deserves emphasis. The MHRA has documented large seizures of counterfeit weight-loss pens sold through unverified online sellers, fake pens that have in some cases contained insulin rather than semaglutide. A delay of a few days while a replacement is arranged through a GPhC-registered pharmacy is far safer than a pen from an unknown source. You can verify any online pharmacy on the GPhC register; nume's registration number is 9012878.

If you have broader questions about your Wegovy prescription or your treatment is newly starting and you have not yet consulted a prescriber, our Wegovy overview covers how the medicine works and who it is licensed for. And if you are weighing up options more generally, our weight-loss treatment page sets out the licensed choices available in the UK. When you are ready to speak to a prescriber, you can start your free consultation, reviewed the same working day.