How Mounjaro Storage Works: Fridge, Room Temperature, and What to Check
Mounjaro (tirzepatide) is a prescription-only, once-weekly injectable medicine supplied as a pre-filled pen. Like many injectable medicines, it requires refrigerated storage before use to maintain its stability.
Unopened pens
According to the product information for Mounjaro, unopened pens should be stored in the fridge at 2–8 °C (36–46 °F). They should be kept away from the freezer compartment and not allowed to freeze — a frozen pen should not be used.
Pens in use or out of the fridge
Once removed from the fridge, a Mounjaro pen can generally be stored at room temperature (below a maximum temperature stated in the patient information leaflet) for a limited period. Check the leaflet that came with your pen, or the electronic Medicines Compendium (eMC) for the exact figure, as the permitted duration and temperature ceiling are defined specifically for this product. Using a pen that has been outside the permitted conditions may affect how the medicine works — when in doubt, speak with your prescriber or pharmacist.
Protecting your pen day to day
- Keep pens away from direct sunlight and heat sources.
- Do not store in a car glove compartment or on a sunny windowsill.
- Do not use a pen that has been frozen, even if it has since thawed.
- Check the expiry date on the pen before each injection.
If you are travelling and wondering how long a pen can safely be outside the fridge, see the related guide on how long Mounjaro can be out of the fridge for more detail. For those using semaglutide, the equivalent guidance is covered in our page on how long Wegovy can stay out of the fridge.
It is also worth knowing how long Mounjaro lasts when kept in the fridge — particularly if you receive several pens at once and want to plan ahead.
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Tracking Your Pens and Doses with GLP Trackr
Keeping on top of storage is easier when you know exactly which pen you are using and when you used it. GLP Trackr's dose logging feature lets you record every injection — date, time, and dose strength — so you always have a clear, timestamped history of your pens.
If you take your pen out of the fridge ahead of a trip or a planned injection day, that log can help you keep track of when the pen was first removed and how long it has been at room temperature. You can note this alongside your injection record in the app, giving you useful context to share with your prescriber if you have any questions about a particular pen.
Dose reminders are another practical feature: a gentle weekly prompt means you are less likely to forget your injection day and less likely to find yourself scrambling for a pen that has been sitting out longer than intended.
For a broader understanding of how Mounjaro works in the body, the guide on how Mounjaro works covers the mechanism behind tirzepatide in plain language.
If you ever have concerns about whether a pen has been stored correctly — or whether a dose is still suitable to use — always contact your prescriber, pharmacist, or healthcare professional. GLP Trackr helps you record and organise your journey; it is not a substitute for professional guidance on your medicine.
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Frequently asked questions.
Unopened Mounjaro pens should be stored in the fridge at 2–8 °C. Once in use, the pen can typically be kept at room temperature for a limited period — check the patient information leaflet or the electronic Medicines Compendium for the exact permitted duration and temperature.
Exposure to temperatures above the limit stated in the product leaflet, or storage beyond the permitted out-of-fridge period, may affect the medicine. If you are unsure whether a pen is still suitable to use, speak with your pharmacist or prescriber before injecting.
No. Mounjaro pens should not be frozen. If a pen has accidentally frozen, it should not be used — contact your pharmacist or prescriber for advice on what to do next.
Wegovy (semaglutide) also has a defined out-of-fridge storage period set out in its patient information leaflet. Check the leaflet or the electronic Medicines Compendium for the specific limits, as they are product-defined and may differ from other injectable medicines.
GLP Trackr lets you log each injection with the date, time, and dose strength, giving you a clear history of when each pen was first used. Dose reminders also help you stay on your weekly schedule without losing track.