Yes, Mounjaro needs to be kept in the fridge, but there is a bit more to it than that, especially if you travel or your pen gets left out by accident. This guide explains exactly how to store Mounjaro, how long it can safely sit at room temperature, and how to keep it in good condition on holiday. For everything else about the treatment, see our complete guide to Mounjaro.
Store Mounjaro in the fridge at 2°C to 8°C and never freeze it. If you need to, it can be kept at room temperature below 30°C for a limited time, and once that window passes the pen should be thrown away. Always check the leaflet that comes with your own pen.
The simple rule: keep it in the fridge
Mounjaro is a biological medicine, which means it can lose its effectiveness if it gets too warm or too cold. The standard storage instruction is to keep your pens in the fridge at 2°C to 8°C, ideally on a middle shelf rather than in the door, where the temperature swings each time you open it.
Keep the pens in their original carton until you use them. The carton protects the medicine from light, which also helps it stay stable. As long as it is refrigerated correctly, Mounjaro stays good to use right up to the expiry date printed on the box.
Can Mounjaro be left out of the fridge?
Yes, within limits. If you need to keep it out, Mounjaro can be stored at room temperature, below 30°C, for a limited period. For most single-dose pens that window is up to 21 days, while the multi-dose KwikPen allows up to 30 days. The safest habit is to treat the shorter figure as your guide and check your own leaflet, because it states the exact limit for the pen you have been given.
Two things are worth remembering. The clock starts the first time the pen leaves the fridge, and putting it back in later does not reset or extend that window. And once the limit has passed, the pen should be thrown away even if it looks fine and still has medicine in it.
A simple trick: when you first take a pen out of the fridge, write the date on the box. That way you always know how long it has left in its room-temperature window, with no guesswork.
What if it gets too warm, or is left out too long?
If a pen has been above 30°C, or out of the fridge for longer than its allowed window, do not use it. Heat can quietly reduce how well the medicine works, even when nothing looks different. Set that pen aside and speak to your pharmacist about a replacement rather than risking an injection that may not be effective. The usual culprits are easy to picture: a bag left in a hot car, a sunny windowsill, or a warm holiday apartment with no fridge. A little forward planning around those situations saves both the medicine and the cost of replacing it.
What if Mounjaro freezes?
Freezing damages the medicine, so a pen that has frozen must not be used, even after it thaws. This is why the door of the fridge and the very back of the shelf, where things can freeze, are best avoided. If you are unsure whether a pen has frozen, treat it as unusable and check with your pharmacist.
Your Mounjaro storage checklist
Travelling with Mounjaro
You can absolutely travel with Mounjaro, it just takes a little planning. Carry your pens in an insulated cool bag with a cold pack, but make sure the pens do not touch the pack directly, as that can freeze them. Keep everything in the original carton so it stays protected from light.
When you fly, always keep your medicine in your hand luggage rather than the hold, where it can freeze or go missing. It helps to carry a copy of your prescription or a note from the pharmacy, and to plan around the room-temperature window so your pens are back in a fridge before it runs out. If you are getting to grips with the basics of treatment before a trip, our overview of how Mounjaro works and what to expect is a useful companion.
How Superior Pharmacy delivers your Mounjaro
Getting your medication to you in good condition is part of the service. We dispatch Mounjaro in discreet, temperature-controlled packaging by a tracked service, so it arrives ready to go straight into your fridge. When you need more, reordering is quick and your details are saved securely, so you are never scrambling at the last minute. If you are just getting started and want to see how storage fits into the wider routine, our full Mounjaro guide walks through the whole journey, from assessment to your first few months.
Frequently asked questions
How long can Mounjaro stay out of the fridge?
It can be kept at room temperature below 30°C for a limited window, up to 21 days for most single-dose pens and up to 30 days for the KwikPen. Check your leaflet for the exact figure, and discard the pen once the window has passed.
Can I still use Mounjaro if I forgot to refrigerate it overnight?
If it stayed below 30°C and is still within its room-temperature window, it is generally fine to use and then keep at room temperature or return to the fridge. If it may have been warmer than 30°C, do not use it and speak to your pharmacist.
Does Mounjaro need to be cold when I inject it?
No. Many people find the injection more comfortable if they let the pen sit at room temperature for a short time beforehand. It does not need to be cold at the moment you use it.
What should I do if my pen has frozen?
Do not use it. Freezing damages the medicine even once it thaws. Set the pen aside and contact your pharmacist about a replacement.
This guide is general information and not a substitute for personal medical advice, and storage details can vary by pen, so always follow the patient information leaflet supplied with your medicine. Mounjaro is a prescription-only medicine supplied after an online assessment and approval by one of our UK-registered independent prescribers.