Storing insulin in Lahore's summer heat

What the label asks for

• Unopened: in the fridge until the expiry date. It may also be kept at room temperature, up to 30°C, for 28 days.
• Opened vial: 28 days, in the fridge or at room temperature.
• Opened SoloStar pen: 28 days at room temperature only. Do not refrigerate it.
• Do not freeze it, and throw it away if it has frozen. Protect it from direct heat and light.

Brands differ, and your own leaflet comes first. As an example, the Lantus (insulin glargine) label gives these rules:

In a Lahore summer

• Keep the pen you are using in the coolest, shadiest part of the house, away from windows, the stove and the geyser.
• When you go out, carry it in a bag in the shade, and bring it home. Do not leave it in a parked car or a motorbike box.
• Keep spare, unopened insulin in the fridge, away from the freezer compartment and not touching ice. Insulin that freezes is spoiled.
• Write the date you opened a pen or vial on it, so you know when its 28 days are up.

The limit that matters most in summer is 30°C. A room with no air conditioning, or with the power out, can go above it, and a parked car or a motorbike box goes far above it.

A power cut

For Lantus, the label allows unopened insulin 28 days at room temperature up to 30°C, so a few hours without the fridge is not in itself the problem. Heat above 30°C is. Move the insulin to the coolest part of the house and check your own brand's leaflet, because other insulins have their own limits.

What a study found about heat

Researchers from Médecins Sans Frontières and the University of Geneva recorded the temperatures in a refugee camp in northern Kenya, which swung between 25 and 37°C, and kept several commercial insulins at those temperatures in the laboratory for four weeks. The insulin stayed within pharmacopoeia standards, and its activity on liver cells matched insulin kept at 2–8°C. The authors concluded that insulin can be kept at such temperatures for the usual four weeks of use.

This is one laboratory study. It does not change the label. It is reassuring if insulin warmed up by accident; it is not a reason to store insulin in the heat.

When to replace it

• It has frozen.
• It is past 28 days from opening (or your brand's limit), even if some is left.
• It has been left in direct sun or a hot car for hours. Do not guess: ask your doctor or pharmacist before using it.

This is general information about storage. It is not a substitute for the leaflet that comes with your insulin or for advice from your doctor.