How to Refrigerate Mounjaro (and What to Do When You Can't)

Step 1, getting your pen home and into the fridge correctly

Mounjaro arrives with nume in tracked, temperature-conscious packaging, but your pen still needs to reach the fridge promptly. A good habit: treat the delivery alert the same way you would a grocery slot, clear a space on the fridge shelf before the courier arrives. The ideal position is the door shelf or a middle shelf set to 2–8°C. Avoid putting the pen at the very back of a top-shelf where the temperature can dip below zero if the fridge runs cold.

Keep the pen in its outer carton until you are ready to inject. The carton shields the solution from light, which can degrade the medicine over time. Mounjaro's pen is pre-filled and pre-set (there is no mixing or assembly) but it still needs that basic protection. If you have any doubt about your fridge's temperature, an inexpensive fridge thermometer is worth buying, and you can find the full answer to whether you have to refrigerate Mounjaro alongside the target range confirmed in the NHS tirzepatide medicines page.

One thing worth knowing before you start treatment: you can read more about how the pen works day-to-day on our Mounjaro injection guide, which covers technique alongside storage.

Step 2, taking the pen out of the fridge for your weekly dose

You do not need to inject cold medicine. Taking the pen out of the fridge around 30 minutes before your scheduled injection gives the solution time to reach room temperature, which many people find noticeably more comfortable. This is common practice with injected medicines and causes no harm to the pen, provided it goes back in (or is used) within the time window.

That window is where the detail matters. Once a pen has left the fridge and sat at room temperature, a clock starts. The SmPC specifies exactly how many days are permitted; that figure is the one to follow, not approximations from any other source. If you need to check it now, the eMC listing for Mounjaro holds the full SmPC with the confirmed figure. Your prescriber or our aftercare team can also clarify this, contact details are on our support page.

Concerns about what happens if the pen has been left out longer than permitted are covered in detail on our Mounjaro not refrigerated page, including when it is necessary to start a replacement.

Step 3 (travelling with your pen (when the fridge isn't an option)

Holidays, overnight stays, work trips) the question of whether you do need to refrigerate Mounjaro constantly is one our prescribers hear regularly. The short answer: ideally yes, but the room-temperature window in the SmPC is precisely designed for situations like these. Plan around it.

For travel, a small insulated cool bag with a gel ice pack (not in direct contact with the pen) keeps the temperature close to the refrigerated range without the risk of freezing. Airline cabin baggage is usually fine, never put the pen in checked luggage where cargo holds can freeze. If you are crossing time zones, keep the pen's carton on you. A full breakdown of the storage rules during travel is on our Mounjaro refrigeration guide, which addresses common scenarios including European travel and longer-haul trips.

The cost of replacing a pen because of improper storage is worth factoring in. If you want context on how Mounjaro is priced in the UK private market (including the background to recent list-price changes) our Eli Lilly UK price increase page covers that clearly.

What to do if something goes wrong with storage

A pen that has frozen must be discarded. Freezing damages the solution in ways that are not visible to the naked eye, the pen may look identical, but the medicine inside is no longer reliable. Do not attempt to thaw and use it. Dispose of it in a sharps container as you would a used pen, and contact your prescriber or our aftercare team to arrange a replacement.

If the pen has exceeded the room-temperature window specified in the leaflet, the same rule applies: discard and replace rather than use a pen whose integrity is uncertain. This is not a theoretical caution, maintaining the cold chain is part of how the licensed product retains its safety and efficacy profile.

If there is visible cloudiness, particles, or discolouration in the solution, do not use that pen regardless of how it has been stored. Mounjaro's solution should be clear and colourless to slightly yellow. Any doubt: speak to a pharmacist or your prescriber before proceeding. Our FAQs page covers a range of common queries, and you can also explore the full context of how Mounjaro is used for weight management on our Mounjaro treatment page.

If you are considering starting or transferring your treatment to a clinician-led service, start your free consultation with nume and a GPhC-registered prescriber will review your case the same day.