Do You Keep Mounjaro in the Fridge? What the SmPC Actually Says

The myth worth correcting first: Mounjaro does not need refrigeration 'sometimes', it needs it by default

A surprisingly common belief is that Mounjaro only needs to go in the fridge if you are not injecting it for a while, or that room temperature is fine as a general rule. That is the wrong way round. Refrigeration at 2°C to 8°C is the default storage condition for every Mounjaro KwikPen; room-temperature storage is the exception, permitted only for a defined window once the pen has already been removed from the fridge.

The reason this matters is straightforward. Tirzepatide is a protein-based medicine and heat degrades it. A pen that has spent too long outside the fridge may look identical to one that has been stored correctly, but its potency can no longer be relied on. You would have no way of knowing from looking at it. Storing Mounjaro properly is not a bureaucratic detail, it is part of getting the treatment to work as the clinical trials showed it could.

The NHS tirzepatide patient information page confirms refrigerated storage as the baseline requirement, and the Mounjaro SmPC on the eMC sets out the exact room-temperature window. Always read both before handling your pen, and if you have questions about your specific situation, the team on our FAQs page is a good starting point.

What the room-temperature rule actually means in practice

There are plenty of legitimate reasons a pen ends up out of the fridge: you forgot to put it back after checking the dose indicator, you left it in a bag on a warm day, or you took it to an appointment and the journey took longer than expected. These things happen. The key is knowing the limit.

The Mounjaro SmPC specifies a maximum number of days the pen may be kept at room temperature (below a defined ceiling), and once that period has been used up, it cannot be reset by putting the pen back in the fridge. Used days are used days. If the pen exceeds the time limit or has been exposed to temperatures above the stated ceiling, it should be disposed of safely and a replacement sourced. Never inject from a pen you are uncertain about.

For anyone travelling, this time limit takes on extra importance. Whether a long-haul flight, a beach holiday or a camping weekend, planning how to keep your pen within its storage conditions requires thinking ahead. Our guide to taking Mounjaro on holiday covers practical approaches in detail, including what to consider for travel to hotter climates.

One thing the room-temperature window does not change: the pen must never be allowed to freeze. If you are wondering whether you need to keep your Mounjaro pen in the fridge, the short answer is yes, as the main body of the fridge is the right place, away from the back wall if that area runs particularly cold in your appliance. A frozen pen, even one that has since thawed, must be discarded.

How to handle and store your pen on injection day

On the day you inject, the advice is to let the pen reach room temperature before use rather than injecting it straight from the fridge, cold medicine under the skin can be more uncomfortable. Leaving it out for around 30 minutes beforehand is a reasonable rule of thumb, though your Patient Information Leaflet should be your reference, not a number from any website including this one.

Before injecting, clean the skin at the injection site. Our prescribers recommend rotating sites, using the abdomen, thigh or upper arm, to avoid tissue changes from repeated injections to the same spot. For site preparation, alcohol swabs are a straightforward option. After the injection, the used pen is clinical waste and needs to go into a proper sharps container rather than a household bin.

If you are new to self-injection, the process can feel daunting at first. That is entirely normal. The KwikPen is designed to be straightforward, and the PIL walks through each step. More detail on the injection process itself is on our Mounjaro injection page, and if a specific question comes up that you cannot find an answer to, our support team is available seven days a week.

When fridge storage questions point to something bigger

Questions about storage often come up when someone is managing treatment on their own for the first time, without as much face-to-face support as they would like. If you are still unsure whether you have to keep Mounjaro in the fridge, our dedicated page walks through the requirement clearly, alongside what to do if your storage situation is not straightforward.

Mounjaro is a prescription-only medicine. A licensed prescriber assesses your suitability, your medical history, and your current medicines before any treatment is agreed. At nume, that review is carried out by a real clinician on the day you submit your consultation, not a chatbot, not a queue. You can read more about the medicines we offer on our weight-loss treatments overview, or explore the full Mounjaro treatment page to understand what the clinical evidence shows. For context on what private treatment costs in the UK and what a transparent price should cover, our guide to getting a Mounjaro prescription explains the landscape honestly.

If you are ready to explore whether treatment is suitable for you, speak to our prescribers through a free consultation, there is no obligation, and the clinical review happens the same day.