Wegovy out of the fridge: how long is safe, and what happens if you go over?

What the official guidance actually says about time outside the fridge

The Wegovy SmPC (published on the Electronic Medicines Compendium and referenced by NHS guidance on semaglutide) sets the room-temperature limit at 28 days at or below 30°C, away from light. That figure applies from the moment the pen first leaves refrigerated conditions, and it applies equally to pens that have been opened and to those still sealed. There is no distinction in the licence between "first use" and "subsequent use"; the timer starts at first removal.

Many people store their travel pen in a cool bag or a coat pocket, which is fine as long as the temperature stays within range. A common slip is leaving the pen in a handbag that then sits in a sunny car for a couple of hours, that heat exposure can compromise the medicine even if the total days out of the fridge are still under 28. The temperature limit matters as much as the day count.

If you are unsure whether your pen has been stored correctly, our guide to Wegovy out of the fridge walks through the key checks to make before using it. Using a heat-damaged pen is not recommended; semaglutide is a protein-based medicine whose structure can be altered by excess heat, and there is no reliable visual test for degradation.

Why the 28-day limit exists: what heat does to semaglutide

Semaglutide is a GLP-1 receptor agonist, a synthetic peptide that mimics a naturally occurring gut hormone involved in appetite regulation and blood glucose control. Like most peptide medicines, it is sensitive to conditions that disrupt its molecular structure: freezing, excessive heat, and direct light can all degrade it. Refrigeration at 2–8°C keeps the molecule stable for the pen's full shelf life. Once outside the fridge, the stability window is limited by cumulative thermal exposure, which is why 28 days at or below 30°C is the tested, authorised threshold rather than an arbitrary round number.

Degraded semaglutide does not necessarily look different. The liquid may appear identical to an unaffected pen. This is why time and temperature are the only practical indicators available to someone who is not a chemist, and why exceeding either one means the pen should go. If you are mid-cycle and have concerns about a pen's history, your prescriber is the right person to ask, not the internet.

For more on what the full Wegovy cold-chain journey looks like from pharmacy to your door, the Wegovy fridge storage guide covers conditions during transit and at home.

Practical rules for keeping track, and when to discard

The simplest system is to write the date of first removal on the pen with a fine permanent marker. Twenty-eight days from that date is your discard deadline. If you put the pen back in the fridge during that period, the counter does not reset, it continues from first removal, cumulative. A pen that went out on the 1st and came back in on the 5th has 23 days of room-temperature allowance remaining, not a fresh 28.

Discard scenarios to act on without hesitation: the pen has been out for more than 28 days in total; the ambient temperature clearly went above 30°C (left in a hot car, on a sunny windowsill, beside a radiator); the pen is past its printed expiry date. In each case, safe disposal means a sharps container, not the household bin. Your local pharmacy can also accept sharps for disposal.

If a pen is genuinely unusable and you need a replacement, that is a conversation for your prescriber. A clinical review is part of that process at nume, and our team is available seven days a week for exactly this kind of aftercare question. You can reach us via the contact page.

What this means if you travel or change your routine

Travel is the scenario that catches most people. A pen in checked luggage can freeze in the hold; one in a pocket in direct equatorial sun can exceed 30°C before lunchtime. The 28-day out-of-fridge allowance was designed for ordinary room-temperature conditions, not extremes. The practical guidance on taking Wegovy out of the fridge covers travel scenarios in more detail, but the short version is: a cool bag or insulating case matters more than most people think.

For those switching between injectable semaglutide and other GLP-1 treatments, storage rules are not interchangeable, tirzepatide (Mounjaro) and semaglutide have different authorised conditions, so check the individual leaflet for whichever pen you are using. If you want a detailed breakdown of how long Wegovy can safely spend outside refrigeration, our guide to semaglutide out of the fridge has the specifics for the molecule across its formulations.

If you are considering starting Wegovy and want to understand the full picture before you begin (eligibility, how treatment works, and what clinical support looks like) you can also read about how weight loss injections such as Ozempic compare before you check your eligibility with our prescribers. A consultation is free, takes a few minutes, and is reviewed the same day by a real clinician.