The UK KwikPen storage rules
The current UK product information says to store the pen in a fridge at 2°C to 8°C and never freeze it. After first use, you can keep the pen out of the fridge for up to 30 days at no more than 30°C. After that, throw the pen away.
Write the date you first used the pen somewhere easy to find. The printed expiry date and the first-use limit are separate checks. An expiry date months away does not extend the life of a pen you have started. The in-use temperature rule also does not cover every shipping situation.
Why a clear liquid is no guarantee
The liquid must look as the leaflet describes. Clear liquid still gives no proof that a pen which overheated or froze is safe to use. A pen can have a bad storage history with no change in colour. If the pen has frozen, the label says do not use it.
Home fridges have cold spots, often near the cooling element. Store the pen where it cannot freeze by accident and follow the handling instructions on the pack. Never put it in the freezer to cool it down faster after a delivery or a trip.
If a delivery arrives warm
Note when the parcel arrived, the state of the packaging and any temperature information supplied. Contact the dispensing pharmacy promptly and ask them to assess the shipment against the product's stability data. The outdoor temperature tells you little about how warm the inside of the parcel became.
A melted ice pack does not automatically ruin a delivery, and a cool parcel on arrival may still have gone out of range in transit. The packaging, the time in transit, tested shipping methods and any recorded temperature problems all count. Keep the pen stored correctly while you wait for advice.
Travel and heat at home
Cars, sunny windowsills and bags left outside get much hotter than the forecast air temperature. A cool bag must stop the pen freezing as well as overheating, so keep the pen out of direct contact with a frozen ice pack. Check how long your cool bag holds its temperature.
Hotel minibars often run at unreliable temperatures. Ask about fridge storage before you arrive if you are carrying an unused pen. On a long trip, plan for power cuts, delayed bags or a change of room, since a pouch alone may not cover these.
When to check before using the pen
Ask a pharmacist before using a pen if you do not know how long it has been out of the fridge, whether it froze or how hot it got. Give them the strength, batch number, expiry date, first-use date and details of the exposure where you have them. The pharmacy can contact the manufacturer when needed.
A pharmacist's assessment of your pen takes priority over general guidance. Storage rules depend on the formulation and the device. A single-dose pen or vial from another country may have different approved limits. Follow the leaflet for the product you were given.
Sources
Your own medicine leaflet and prescriber come first. A source from another country does not mean the same rule applies in the UK.
- Mounjaro UK Summary of Product Characteristics, updated September 2026 medicines.org.uk
- Mounjaro UK patient information leaflet medicines.org.uk
- NHS Fit for Travel: travelling with medicines fitfortravel.scot.nhs.uk
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