Mounjaro Expiry: How to Check the Date and Store Your Pen Correctly

Step 1, Read the date on the box and on the pen itself before you inject

The expiry date appears in two places: on the outer carton and on the label wrapped around the pen. Both should match. The format is month and year (MM/YYYY), which means the pen is valid through to the last day of the printed month, not the first. So a pen marked 07/2026 is usable up to and including 31 July 2026, but not on 1 August.

Check both labels when the delivery arrives. Your Mounjaro pen ships in plain, unbranded packaging via DPD with a tracking link, so you can be at home to receive it promptly and get it straight into the fridge. Checking the date at the door takes seconds and saves any doubt later.

If the dates on the box and pen differ, or if the print is damaged and unreadable, do not use the pen. Contact your dispensing pharmacy straight away. For general questions about your supply, the nume contact page is the quickest route to our team.

Step 2, Store the pen correctly from arrival through to use

Mounjaro is a biological medicine and temperature matters. Unopened pens must be refrigerated between 2°C and 8°C, the fridge door shelf is fine as long as temperatures stay within range. The pen must not freeze. If your fridge runs cold and the pen has been exposed to freezing temperatures, do not use it.

There is a permitted room-temperature storage window for times when refrigeration is not possible, travelling, for instance. The exact duration and upper temperature limit are set out in the Mounjaro SmPC on the eMC. Because the specific window can change with updated product information, we always direct readers to the current leaflet rather than quoting a fixed number of days here.

Keep the pen in its original tray inside the carton, away from direct light. If you are unsure whether storage conditions have been met at any point (perhaps after a long journey or a fridge failure) speak to your prescriber or pharmacist before injecting. The guidance on the Mounjaro injection page covers practical prep steps alongside storage.

Step 3, Understand the expiry rules once you have taken your first dose

A Mounjaro KwikPen contains four weekly doses. The moment you use dose one, the post-opening storage clock starts. The timeframe during which the remaining three doses must be used is specified in your Patient Information Leaflet. The pen does not expire at the end of the printed month if you open it partway through, the opening-date rule applies instead, and it is typically shorter than the remaining time to the printed date.

There is detail worth reading separately on this question. The rules around Mounjaro expiry once opened and storage after opening are covered in dedicated pages that go into the specifics. The short version: once the pen is in use, the Patient Information Leaflet is the authority, and storing it back in the fridge between doses is essential.

One practical note: if your titration schedule means a dose increase partway through a box, confirm with your prescriber before opening a new pen, you want to use existing doses in order and avoid wasting a pen that still has doses remaining.

Step 4, What to do with a pen you cannot use

An expired pen, a pen that has been frozen or stored outside permitted temperatures, or one where the printed date is illegible should not be injected. Do not try to keep it on the basis that it might still work, and if you want to understand exactly how to read the date printed on your pen, our page on the Mounjaro expiry date explains the format and what it means in practice. Degraded tirzepatide may simply be less effective, but there is no way to assess this at home, and if you are ever uncertain about the date on a generic or alternative supply, our tirzepatide expiry date guidance covers the same rules as they apply to the active ingredient.

Disposing of a used or unusable pen safely means placing it in an approved sharps container rather than the household bin or recycling. Your local pharmacy will accept sealed sharps containers for disposal. Needles should be removed and disposed of separately after each dose; do not recap or reuse them.

If you are thinking about the longer-term cost picture of keeping a supply current, the Mounjaro pricing page sets out what private treatment involves. And if a question arises mid-treatment that your leaflet does not fully answer, the nume FAQs and your prescriber team are both available, our clinical team reviews every repeat order before dispatch, which is one reason that supply stays clinically supervised throughout.

The NHS medicines page for tirzepatide also contains storage and handling guidance that is regularly updated and worth bookmarking.