Does semaglutide need refrigeration — and what happens if it gets warm?

You open the fridge, find the pen has been sitting on the counter since yesterday, now what?

It happens more often than you might think. A question our prescribers hear most weeks is some version of: "I left my Wegovy out overnight, is it still safe to use?" The honest answer is: it depends on how long, and at what temperature.

Semaglutide is a biological medicine, which means its structure can degrade if it gets too warm for too long. Eli Lilly's tirzepatide and Novo Nordisk's semaglutide both follow a cold-chain model during manufacture and distribution. If you have ever wondered whether Wegovy requires refrigeration and what the rules actually mean day to day, the short answer is yes: once a Wegovy pen is in your hands, it continues to need refrigeration between 2°C and 8°C until the moment you start using it. That means the back of a fridge shelf, not the door and certainly not the freezer, freezing damages the pen irreversibly.

When a pen is actively in use, semaglutide can tolerate room temperature for a set period. The Patient Information Leaflet published on the electronic Medicines Compendium gives the precise number of days for your specific pen format; this is the authoritative source and the one to follow. A vague "a few weeks" figure from a forum is not a substitute for the actual PIL. If you are unsure whether your pen has been compromised, contact your pharmacy before injecting. The first injection guide on this site also covers what to check before you use a new pen.

If the pen looks cloudy, has visible particles, or has changed colour, do not use it regardless of the storage history. A damaged pen is not just ineffective, it carries a small but real risk of an injection-site reaction.

What semaglutide refrigeration means in practice at home

Most people store their Wegovy pens in a consistent spot in the main fridge compartment without any issue. A few practical points make a real difference.

Keep the pen in its original box until use. The cardboard protects it from light, which can also degrade the medicine over time. The fridge door is tempting because it is easy to reach, but door temperatures spike every time the fridge opens; the middle shelf is steadier. Keep the pen away from anything that might freeze near the back wall.

If you share a fridge (with housemates, family or in a workplace kitchen) a small labelled cool bag inside the fridge keeps the pen contained and makes it less likely someone else moves or accidentally freezes it. There is no need for a dedicated medical fridge for most people; a standard domestic fridge at the correct setting is fine.

For anyone thinking about the cost of treatment alongside these practical commitments, the Wegovy price comparison guide sets out what a full private prescription typically includes in the UK, which is worth understanding before you start.

Disposing of used pens correctly matters too. Each pen and needle is clinical waste. A sharps container is the safe option; most councils collect them, or your pharmacy can advise on local disposal routes.

Travelling with a semaglutide pen: airports, hotels and heat

Travel is where semaglutide refrigeration gets more complicated, and where some planning ahead pays off. The full detail on travelling abroad with Wegovy is covered in the Wegovy travel storage guide, but here is the core of it.

At airports, carry your pen in hand luggage, not checked baggage, hold temperatures are unpredictable and can drop well below freezing. Most airline security lanes accept medical sharps and pens without issue if you carry a letter from your prescriber or pharmacy confirming the medicine. Declare the pen and needles before screening rather than hoping they go unnoticed.

In the cabin, keep the pen in a small insulated pouch rather than the overhead locker, where temperatures drop on long-haul flights. A good-quality medical cool bag with an ice pack (checked that the pack itself stays above 0°C to avoid freezing the pen) handles most journeys of up to 12 hours comfortably.

Hotels almost always have a fridge in the room, but if yours does not, a quick call to reception usually resolves it. Some hotels store medicines in a kitchen fridge on request. It is worth arranging this before arrival rather than improvising at check-in.

The differences between Wegovy and Ozempic are worth knowing here too, Ozempic is licensed for type 2 diabetes, not weight management, and its storage conditions differ slightly from Wegovy's, so never assume the rules are interchangeable.

When to contact your pharmacy or prescriber about storage

A few situations warrant a direct conversation rather than a judgment call on your own. Contact your pharmacy or prescriber if: the pen was left somewhere very warm (a car in summer, direct sunlight on a windowsill) for more than a couple of hours; the pen has been frozen, even briefly; the liquid looks different from when you started the pack; or you are simply not sure and want a second opinion before injecting.

Wasting a pen feels frustrating and expensive. But injecting compromised semaglutide is not a small risk, the medicine may simply not work, or it may cause an unexpected reaction at the injection site. A pharmacist's view on a storage query takes minutes and is always the right call when there is genuine doubt.

For anyone earlier in their treatment journey, the full overview of how Wegovy works covers mechanism, licensing and what to expect week by week. And for a broader look at the weight-loss treatments available through a private clinician-led service in the UK, the treatment options page is a useful starting point. If you have already decided semaglutide is right for you, speak to our prescribers through a free consultation and your pen (stored correctly from day one) can be with you the next working day.