How Long Does Mounjaro Last in the Fridge Unopened?

Mounjaro (tirzepatide) is a prescription-only, once-weekly injectable medicine supplied as a pre-filled pen. Like many injectable medicines, it needs to be kept cold but must never be frozen — freezing damages the solution and the pen should not be used if it has been frozen.

The basic storage rules for an unopened pen

• Temperature: store in a refrigerator at 2 °C to 8 °C. Keep it away from the freezer drawer and from the back wall of the fridge where temperatures can drop unpredictably.
• Light: keep the pen in its original carton to protect it from light.
• Expiry date: never use a pen past the date printed on the label, even if it has been stored correctly throughout.
• Freezing: a pen that has been accidentally frozen should not be used. Contact your prescriber or doctor for guidance.

What changes once a pen is opened?

Once a pen has been used for the first time, the storage rules change. You can read more about how long an opened Mounjaro pen lasts in the fridge and general Mounjaro fridge storage guidance for a fuller picture of in-use rules.

It is also worth knowing that if you need to take a pen out of the fridge temporarily — travelling, for example — there is a limited period during which it may be kept at room temperature. Check the patient information leaflet that came with your pen for the specific window, and do not exceed it. This is separate from the refrigerated shelf life of an unopened pen.

If you are thinking about how many pens you might go through over time, our guide on how long one Mounjaro pen lasts covers what to expect from each device.

One practical way to avoid storage worries is to keep a clear record of every dose you take — so you always know exactly where you are in your current pen and when you are likely to need the next one. GLP Trackr's dose logging feature lets you record each injection with the date, dose strength, and time, giving you a running log you can glance at any time.

Paired with dose reminders, logging each shot means you are far less likely to lose track of your schedule or discover a pen has gone unused past its expiry date. The app builds a picture of your injection history that you can bring to your prescriber appointments — useful if you want to discuss supply timing or pen usage.

For a broader understanding of how Mounjaro works and what to expect on your journey, visit our guide on how Mounjaro works.

If you ever have any doubts about whether a pen has been stored correctly — or if you are unsure whether it is still safe to use — contact your prescriber or doctor before using it. They know your full history and are best placed to advise. Storage questions about your specific pen are also answered in the patient information leaflet that came with it.

Keep your injection schedule logged and your next dose ready — download GLP Trackr on the App Store or Google Play and start your free 7-day trial today.