Wegovy Expiry Date: The Facts Behind a Common Misconception

The myth that a 'use by' date is just a manufacturer's precaution

A question our prescribers hear most weeks is whether the expiry date on a Wegovy pen is conservative, a cushion of caution that leaves plenty of room to use a pen a week or two late. It is not. The date printed on the label is the end point of Novo Nordisk's controlled stability testing under refrigerated conditions. Beyond it, the concentration of semaglutide cannot be guaranteed to sit within the licensed therapeutic range. A pen that looks identical to a fresh one may deliver a meaningfully lower dose, not enough to cause visible alarm, but enough to undermine treatment.

This matters most for people who have stocked up during a supply shortage or who find an older pen at the back of the fridge. The risks of using an expired Wegovy pen are not dramatic in the way a contaminated counterfeit might be, but reduced efficacy is a real and documented consequence of degraded biologics. The right call, always, is to check the date before you inject.

The NHS medicines guidance for semaglutide is clear that storage and expiry instructions in the Patient Information Leaflet should be followed precisely, refer to that leaflet or to the NHS semaglutide medicines page for the current figures, since packaging updates can occasionally revise shelf-life information.

What the expiry date does not tell you about an open pen

The printed date applies to a pen stored correctly and unopened. Once you attach a needle and take your first dose, a separate countdown begins. The Wegovy Patient Information Leaflet specifies how long an in-use pen remains usable, and that figure is shorter than the remaining time to the printed date. This is the detail that catches people out. Someone who opens a pen in January with an April expiry date may assume the pen is good through April. It is not necessarily so once use has started.

For the precise in-use window relevant to your specific pen, the rules around Wegovy's expiry after opening are covered in detail separately. The short version: treat the leaflet's in-use figure as an absolute limit, not a guideline. Write the opening date on the pen with a marker if that helps you track it.

A different but related question is what happens with semaglutide's expiry across formulations, the injection and the newer oral tablet have different packaging and different timelines, and it is worth understanding which applies to your treatment.

Storage conditions that can move the effective expiry earlier

The printed date assumes unbroken cold-chain storage at 2–8°C. Real-world storage rarely achieves lab conditions throughout a pen's entire life. A pen left in a hot car for an afternoon, placed next to the freezer element, or carried through airport security in a bag that overheats, each of these can accelerate degradation. The pen may still look normal. The solution is not to inspect the liquid and make a judgement call; it is to store correctly from the start.

Practical points worth knowing. Wegovy pens can be kept at room temperature (below 30°C) for a limited period if refrigeration is temporarily unavailable, the leaflet gives the exact permitted days, and those days count towards the overall usable life of the pen, they do not reset when it goes back in the fridge. If a pen has been frozen accidentally, do not use it even if it has thawed and looks clear. Freezing damages the suspension in a way that is not visible to the naked eye.

If you are unsure whether your pen has been stored correctly, contact your prescriber or pharmacy before using it. For questions about how to dispose of a pen safely, a sharps container is the correct disposal method, never a household bin.

When to get advice and what to do with an expired pen

Do not inject from a pen that has passed its expiry date or its in-use window. Do not use a pen that looks cloudy, discoloured, or has visible particles, regardless of the date. If you notice any of these things, the right step is to contact your prescriber, not to push on and hope. A single missed dose while you wait for guidance is far less disruptive than injecting a compromised dose and dealing with the consequences.

Suspected side effects from any dose, including those where product quality is in question, can be reported to the MHRA via the Yellow Card scheme. That reporting system exists precisely to catch patterns that might not be obvious from a single patient's experience.

If your treatment plan is affected by an expiry-date issue (a delayed delivery, a pen damaged in transit, uncertainty about what happened during travel) the place to start is a conversation with a prescriber. For context on what the evidence says about taking semaglutide after the expiration date, that is covered separately. If your broader Wegovy supply or treatment questions are unresolved, our team at weight-loss treatments can arrange a review. Speak to our prescribers, they deal with exactly these practical questions and can advise on your specific situation.