Wegovy Expiry: the Myth That Could Cost You a Dose

The myth: 'It looks fine, so it must still be fine'

Clear, colourless liquid tells you very little about a medicine's potency. Semaglutide is a peptide (a chain of amino acids) and peptide medicines break down at the molecular level long before any cloudiness or discolouration appears. This is why the NHS guidance on semaglutide is unambiguous: do not use a pen that has passed its expiry date, and do not assume a pen is still effective just because it looks normal to the eye. The date stamped on the label is not the manufacturer being overly cautious. It reflects real stability data gathered during clinical testing, and once that date passes the medicine cannot be guaranteed to perform as the prescriber intends.

The same logic applies to a pen that has been left out of the fridge for longer than permitted. You cannot reverse thermal degradation by putting the pen back in the cold. The damage, invisible as it is, is already done.

Two expiry dates: what the label says vs. what happens once the pen leaves the fridge

Your Wegovy pen should be kept refrigerated between 2°C and 8°C from the moment it is dispensed until you are ready to use it. The date printed on the pen is valid only if that cold chain has been maintained throughout. Once a pen is kept at room temperature (for travel, for convenience, or simply because it was left out) the in-use window is considerably shorter. If you want a clear explanation of how to read and interpret the date on your pen, our Wegovy expiry date guide walks through exactly what each date means and where to find it. The Wegovy SmPC on the eMC holds the manufacturer's authorised storage instructions in full. Reproducing a specific number of days here would be doing you a disservice, because the right answer for your pen, your storage conditions and your dose is the one in that leaflet, not a figure recalled from an article.

There is a practical timing issue worth naming plainly. If your pen arrives just before a bank holiday, or you ordered on a Friday and plan to start Monday, check where it will spend the weekend. A pen sitting on a warm worktop over a long holiday is not the same pen it was on Friday morning. Refrigerate it as soon as it arrives. If life intervened and you're not certain how long it was left out, speak to your prescriber before injecting, that is exactly the kind of question our support team is available seven days a week to help with.

What to do with an expired or suspect pen

Do not inject an expired pen, and do not inject one you suspect has been stored incorrectly. The risk is not that something dangerous will happen in the acute sense, it is that you may inject a pen with reduced potency and not realise your dose was compromised. Over weeks, that matters for your progress and your clinical review.

Dispose of used and expired pens properly. Sharps go into a designated sharps container before being taken to a local disposal point; your council's website or a community pharmacy will tell you where the nearest one is. Never put pens in general household waste or recycling.

If you are looking at a pen and genuinely unsure whether it is still within its safe window, the right move is to contact your prescriber. At nume, a real clinician (not an automated response) looks at your queries. You can find out more about the clinical team behind the service on our prescribers' page. Questions about how long a Wegovy pen lasts once opened and what to do with an expired Wegovy pen are among the most common ones our team fields.

Expiry and the broader picture of safe Wegovy use

Expiry dates sit within a wider set of handling rules that are easy to follow once you know them. Rotate injection sites. Change needles with each injection. Keep the pen capped when not in use. None of this is complicated, but it is the kind of detail that tends to get glossed over in the first week of treatment when the focus is on getting the dose right. The question of whether Wegovy expires comes up frequently precisely because people are conscientious about getting this right, which is the right instinct.

For people who want a broader look at how semaglutide storage compares with other injectable treatments, the semaglutide expiry page covers the shared principles across GLP-1 medicines. And if you are at the stage of considering treatment or thinking about next steps, our weight-loss treatment overview sets out what is available and how private prescribing works. When you are ready, you can speak to our prescribers through a free consultation, same-day clinical review, no waiting list, and your questions answered by someone qualified to answer them.