How Long Can You Leave Mounjaro Out of the Fridge? (October 2026)

01 · The core answer

How long can Mounjaro stay out of the fridge?

Once you have started using a pen, it can be kept out of the fridge not above 30°C for up to 30 days. After that it must be thrown away.¹

Keep the cap on to protect the pen from light. Note the date you first took it out, so you can count the days accurately.

02 · What next

What should you do now?

If your in-use pen has been out for less than 30 days and stayed not above 30°C, carry on as normal; if an unopened pen has been out of the fridge, check with the pharmacy before using it. If you are unsure, read our guide on what happens if you leave Mounjaro out, or see our out-of-fridge safety guide. If you need a new pen, you can start from the Mounjaro pen page.

03 · Unopened pens

Unopened pens out of the fridge

Unopened pens should be kept in the fridge and keep until the expiry date printed on the box.¹³ If one has been out, check with the pharmacy before using it rather than relying on a remembered day limit. Figures circulating online often come from other countries' labels.

For a related question, see leaving Mounjaro out overnight.

04 · Travel and heat

Travelling and hot weather

You can fly with Mounjaro. Carry pens in hand luggage, because hold luggage can fall below freezing, ideally in a cool bag with the prescription label or a copy of your prescription.¹ Most holidays need no special arrangements, but for hot climates use an insulated pouch. Do not use a pen that has been above 30°C.

Our unrefrigerated storage guide covers more scenarios.

05 · Is it still good?

How to tell if a pen has gone bad

The solution in a good pen is clear and colourless. Do not use a pen that has been frozen, looks cloudy or discoloured, has particles in it, is past its expiry, or has been out of the fridge for more than 30 days, or above 30°C in use.¹³ If packaging or supply ever seems wrong, check the pharmacy on the GPhC register and contact it before injecting.

06 · Stretching a pen

Can you make a pen last longer?

Each pen contains four weekly doses, and the 30-day limit applies once it is in use.¹ Spreading doses out or taking smaller amounts is not licensed and not supported by the pen's design. If you want to know how long a pen lasts in practice, see how long you can keep Mounjaro out.