Does Semaglutide Expire After 28 Days? The Storage Truth

The misconception worth correcting first: the 28-day limit is about temperature, not an automatic expiry countdown

A lot of people read "use within 28 days" on the Wegovy leaflet and assume the pen starts a countdown the moment it leaves the pharmacy. That is not what the guidance means. The 28-day window is triggered by removal from refrigeration, not by dispensing date or first injection. A pen sitting in your fridge, correctly sealed and at 2–8°C, is fine until the printed expiry date, full stop. The NHS medicines page for semaglutide is clear on this distinction: refrigerated storage preserves the medicine for its full licensed shelf life; room-temperature storage introduces the 28-day cap.

The practical implication is straightforward. If your pen arrived cold, went straight into the fridge door and has stayed there, you do not have a 28-day deadline pressing on you. If you took it out for a trip, left it on the bathroom shelf, or have been carrying it in a bag, the clock started from that point. Keeping a note of the date you first took your pen out of the fridge is a simple habit that removes any guesswork.

For anyone who wants to understand whether and how Wegovy expires, including what the printed date on the pen actually means versus the room-temperature window, there is more detail available. The NHS semaglutide medicines page covers storage alongside other practical information about the medicine. The Mounjaro SmPC on the eMC follows the same refrigeration-first logic for tirzepatide, so the pattern is consistent across this class of medicines, even though the two are different drugs.

What counts as acceptable room-temperature storage (and what quietly invalidates a pen

"Room temperature" in pharmaceutical terms means below 30°C) not whatever your kitchen happens to be on a warm July afternoon. In practice, many UK homes in summer can briefly exceed that in south-facing rooms, and cars sitting in direct sun can reach temperatures that would compromise a pen within minutes. The Wegovy Patient Information Leaflet does not give a lower bound for this window; any environment between roughly 15°C and 30°C is generally acceptable, but the SmPC is the authoritative reference for the exact figures, and our prescribers always point patients there rather than to memory.

Direct light is a separate hazard. Keep the pen in its original carton whenever it is not in use, that cardboard is doing a job. Exposing semaglutide to prolonged sunlight can degrade the medicine independently of temperature.

Freezing is an irreversible problem. A pen that has been accidentally frozen (left in a bag in a very cold car overnight, stored in the wrong part of the fridge where the back panel freezes items) should not be used. The appearance of the solution may look unchanged, but the structural integrity of the molecule can be affected. If you are uncertain whether your pen froze, do not inject it; contact your prescribing team or pharmacy. Detailed practical questions about how Wegovy fares specifically in fridge conditions come up often enough that we have answered them separately.

Once 28 days have passed at room temperature: what to do with the pen

An out-of-fridge pen that has been at room temperature for more than 28 days should not be used, even if doses remain in it. This is uncomfortable if the pen is not empty (a partially used pen represents real cost) but injecting a medicine that has exceeded its validated storage window is not a sensible trade-off. Semaglutide that has degraded may simply be less effective, or in extreme cases could cause unexpected reactions.

Disposal is straightforward. Used or expired pens, like all sharps, should go into an approved sharps container rather than household waste. Your local council or pharmacy will advise on collection. If you find yourself regularly running up against the 28-day window because your injection schedule has slipped or doses have been missed, that is a clinical conversation worth having. A prescriber can help you think through timing, and our frequently asked questions cover some of the common scenarios around missed doses too, though the specific guidance for your situation always comes from the person who prescribed for you.

On the broader question of how semaglutide expiry works across different scenarios, including both the injection and the newer oral form, there is more detail available if you want to dig into it.

Keeping track: the small habits that prevent a wasted pen

The 28-day rule catches people out most often during holidays and travel. Wegovy pens are not small or cheap, and discovering mid-trip that a pen has been sitting unrefrigerated for five weeks is genuinely frustrating. A few straightforward habits prevent most of this.

Write the date on the box when you first move a pen out of the fridge, a marker pen on the carton takes three seconds. For longer trips, a small insulated cool bag with an ice pack buys considerable peace of mind. If you are travelling by air, keep the pen in your carry-on luggage in its original carton; hold baggage can freeze at altitude. For anyone planning extended travel, it is worth discussing timing with a prescriber before you go.

The question of using a Wegovy pen after 30 days out of the fridge is one our prescribers hear regularly, and the short answer is that the guidance is firm: 28 days is the limit. Questions about cost, repeat prescriptions and what a full clinical review looks like before your next supply are addressed on the Wegovy pricing page. If you are considering whether Wegovy is the right treatment for your situation, checking your eligibility with a free consultation is the clearest place to start, a GPhC-registered prescriber, not a form-processor, reads every submission the same day.

When your next pen does arrive (tracked by DPD, in plain unbranded packaging that tells no one what is inside) it will come cold-packed and ready to go straight into the fridge. That cold chain matters, and it is part of why the supply route you use for a prescription medicine is worth thinking about carefully. If you use a refillable injection pen for semaglutide, the storage rules above apply in exactly the same way, so the same habits around dating and refrigeration still protect you. The GPhC pharmacy register lets you verify any online pharmacy in seconds; it is the simplest due-diligence step available to you.