Does Semaglutide Go Out of Date — and What Happens If It Does?

What the expiry date on a semaglutide pen actually means

The date printed on a Wegovy pen is the manufacturer's stability guarantee: Novo Nordisk tested the product under controlled conditions and confirmed it remains within its licensed specification until the last day of that month. After that, the medicine may still look, smell and handle identically (semaglutide solution is clear and colourless) but chemical degradation can mean you're not receiving the dose stated on the label. That matters at every stage of treatment, but particularly during titration, when the body is calibrating its response to each step.

Using out-of-date semaglutide isn't something a prescriber would sign off on, and it would void the clinical basis on which your dose was approved. If you find a pen that has passed its date, the right call is to dispose of it safely (a pharmacist or sharps bin) and contact your prescriber before your next dose. The semaglutide overview on this site covers what the medicine is and how it works for those who want the wider picture.

One detail worth knowing: the expiry refers to the last day of the printed month, not the first. If you want a closer look at how and why semaglutide can go off, including the science behind degradation, that page goes into the detail in full. A pen marked 06/2026 is within date on 30 June 2026.

The in-use window is different from the overall expiry, and often shorter

Once you remove a Wegovy pen from the fridge and start using it, a separate countdown begins. The Patient Information Leaflet (and the Wegovy use-by-date guidance) sets out the specific in-use period; always defer to that document rather than any general figure online, because the rule differs between pen formats and may be updated with new approvals.

The practical upshot is that a pen sitting in the fridge door alongside your groceries isn't accumulating infinite usable life, it has a fixed window from first use, regardless of how far from the printed expiry it is. People who keep a pen at the back of a gym bag and then rediscover it three months later are in a different position from someone who used their most recent pen on schedule and has a fresh one ready.

If you're ever genuinely unsure whether a pen you've already started is still within its in-use window, the honest answer is to contact your prescriber or the pharmacy that dispensed it. Guessing the date wrong in either direction carries real risk: an ineffective dose delays progress, and an out-of-condition pen is not one the clinical evidence supports using.

Refrigeration, room temperature and what goes wrong in transit

Wegovy pens should be stored in a refrigerator at 2–8°C. They can be kept at room temperature for a defined period when needed (useful for travel or if a delivery arrives warm) but the exact window is specified in the SmPC on the eMC (the electronic Medicines Compendium), and that figure is the one that governs. Generic guidance circulating online sometimes quotes different numbers, and the rules for the new 7.2mg pen format may not match older published summaries.

Extreme temperatures in either direction are the real concern. A pen that has frozen (even briefly) should not be used, as freezing can denature the protein-based molecule and alter its structure. Direct sunlight and prolonged heat carry a similar risk. If a pen arrived in a DPD box during a warm week and felt warm to the touch, the right step is to contact the dispensing pharmacy before administering it. At nume, our prescribers are available seven days a week for exactly these situations.

For anyone comparing costs and wondering whether buying from an unverified source saves money, it's worth noting that the cold-chain integrity of those pens is unknown. Storage failures won't always be visible. The Wegovy price comparison page sets out what legitimate UK supply looks like and why provenance is part of what you're paying for.

When to speak to your prescriber rather than making the call yourself

This is the frame the page has been building toward. The decision tree is genuinely simple once the facts are clear: if a pen is within its printed expiry, stored correctly and within its in-use window, use it as prescribed. If any one of those three conditions is in doubt, stop and call.

A prescriber reviewing your case can advise whether to wait for a replacement pen, bridge with a prior dose, or adjust timing, and they can make that call quickly. The NHS overview of semaglutide on the NHS website also covers storage basics in patient-friendly language and is worth bookmarking alongside your PIL. Questions about expiry are among the most common storage queries our clinical team receives; there's no embarrassment in asking.

If you're newer to Wegovy and still getting your head around the treatment itself, the Wegovy treatment page covers the licensed indications, the dose schedule and what clinical oversight looks like in practice. Those who are exploring compounded or alternative formulations may also find it useful to read about Olympia semaglutide, which explains what that option involves and how it differs from the branded pen. And if you're considering whether a private route is right for you, checking your eligibility takes a few minutes and is reviewed the same day by a GPhC-registered prescriber.