How Mounjaro Should Be Stored — and Why It Matters
Mounjaro (tirzepatide) is a pre-filled injection pen that must be stored in a refrigerator at 2–8 °C (36–46 °F) when not in use. This applies from the moment you receive the pens until you are ready to inject. Exposure to temperatures outside this range — particularly heat or direct sunlight — can degrade the medicine and make it less effective.
Before your injection
Many people find that letting the pen sit at room temperature for a short period before injecting makes the injection more comfortable. Check the patient information leaflet that came with your pen for the specific time recommended, as it can vary by product version. Always follow the guidance in that leaflet or ask your prescriber or doctor if you are unsure.
Can a pen be used after being left out?
Mounjaro pens can generally be kept at room temperature (below 30 °C / 86 °F) for a limited period — check the leaflet that came with your pen for the exact number of days your specific pen is rated for, as product information is the most reliable source for this figure. Once a pen has been stored at room temperature for longer than that window, it should not be used. If you are unsure whether a pen is still safe to use, contact your prescriber or a pharmacist rather than guessing.
What to avoid
- Do not freeze Mounjaro pens — a pen that has been frozen should not be used.
- Avoid storing pens near the freezer compartment or against the back wall of the fridge, where freezing can occur.
- Keep pens away from direct light; store in the original carton where possible.
- Do not leave pens in a car, bag in direct sun, or anywhere that may become hot.
For authoritative storage guidance, the electronic Medicines Compendium (eMC) carries the full Summary of Product Characteristics for Mounjaro, which includes detailed storage conditions.
If you have questions about what to do when a pen has been stored incorrectly, see our related guide on what happens if your Mounjaro pen has not been refrigerated for more context on that specific situation.
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Keeping Track of Your Pens With GLP Trackr
One of the easiest ways to avoid storage mistakes is to stay on top of exactly where you are in your injection schedule — and that is where GLP Trackr can help.
The app's dose logging feature lets you record the date and time of every injection, so you always know when your last pen was used and when your next one is due. This makes it much easier to plan ahead — for example, knowing how long a pen will need to be out of the fridge before your next injection day, or whether a pen left out accidentally still falls within your usable window.
The dose reminder feature sends a gentle nudge on your injection day so a weekly dose is never simply forgotten — reducing the chance of a pen sitting unused and unrefrigerated for longer than intended.
For a broader look at everything covered in the Mounjaro journey, visit our complete Mounjaro tracking guide. And if you are also curious about storage rules for Wegovy, our guide to Wegovy and refrigeration covers the same ground for semaglutide pens.
GLP Trackr is a tracking and journaling app — it is not a substitute for the advice of your prescriber, pharmacist, or the patient information leaflet that came with your medication. If you are ever uncertain whether a pen is safe to use, always check with your healthcare professional rather than relying on memory alone.
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Frequently asked questions.
Yes. Mounjaro pens should be stored in a refrigerator at 2–8 °C until you are ready to use them. Incorrect storage can degrade the medicine. Always follow the storage instructions in the patient information leaflet that came with your pen.
Mounjaro pens can generally be stored at room temperature below 30 °C for a limited period — check the leaflet that came with your specific pen for the exact number of days. Once that window has passed, the pen should not be used. When in doubt, ask your pharmacist.
Check how long it was out and compare this with the room-temperature storage limit in your patient information leaflet. If it was left out for longer than permitted, or in excessive heat, contact your prescriber or pharmacist before using it. Do not guess — wasting one pen is far safer than using a compromised one.
No. A Mounjaro pen that has been frozen should not be used. Store pens away from the freezer compartment and the back wall of the fridge to prevent accidental freezing. If you think a pen may have frozen, speak to your pharmacist before using it.
GLP Trackr lets you log every injection with its date and time, so you always know when your last dose was taken and when the next is due. Dose reminders help ensure pens are not left unused for longer than intended. The app is a tracking tool, not a replacement for your patient information leaflet.