Living with diabetes blog

Beware summer extremes with insulin

By Nancy Klobassa Davidson, R.N. and Peggy Moreland, R.N., C.D.E. June 17, 2011

With summer arriving in Minnesota and many other places, I'd like to talk about how to manage insulin storage in extreme temperatures such as this season brings.

A number of years ago, I met with a client who used a rapid insulin pen for meal dosing. She shared with me a story of how she attended the county fair on an exceptionally hot day, and had placed her insulin pen in the back pocket of tight jeans and walked around the fairgrounds all day. She used the pen for covering meals eaten at the fair, and her blood sugars were running higher than normal, but she related this to all the junk food. The next day her blood sugars continued to run high and when she took her (rapid) insulin, it didn't seem to affect her blood sugar level at all; in fact, it was like she was taking water instead of insulin. She wondered if the heat had affected her insulin, so she switched to a new insulin (disposable) pen, and soon after her blood sugars started to drop.

Has this or something similar happened to you?

I looked at insulin manufacturers' websites and found that for the majority of all types and brands of insulin, the maximum temperatures recommended are as follows:

  • Opened room temperature insulin should not exceed 86 F (30 C) with the exception of Lantus, which should not exceed 77 F (25 C).
  • Most manufacturers of insulin recommend discarding insulin if it exceeds 98.6 F (37 C).

Other non insulin diabetic injectable medications:

  • Glucagon and Byetta should not exceed 77 F (25 C).
  • Symlin should not exceed 86 F (30 C).

Avoiding potential problems

  • Temperatures exceeding manufacturer's recommendations for insulin/medications

Store your insulin in the refrigerator, in an insulated case or cooler with a freezable gel pack, or use a cooling wallet. Cooling wallets are available through many diabetes supply companies and keep insulin vials, pens and pumps cool at a safe temperature without the need for refrigeration or ice. The wallets have a liner filled with crystals. The liner is immersed in cold water for 10-15 minutes, and placed back into the wallet, along with the insulin. It works by relying on the process of evaporation for cooling, can keep insulin cool for up to 48 hours, and is reusable.

Remember, after opening a vial of insulin or starting a new insulin pen, the insulin loses its potency and should be thrown away after a certain number of days, depending on the manufacturer's guidelines. Generally, most vials of insulin are good for 28 days after opening with the exception of Levemir (detemir), which is good for 42 days. Other pens are good for 10, 14, 28 or 42 days. Check the medication insert.

  • Avoid temperature extremes
    Never freeze insulin or expose it to extremely hot temperatures or direct sunlight. Never leave it in your car. Never place it directly on ice or an ice pack.
  • Watch for changes in insulin appearance
    Throw away insulin that is discolored or contains solid particles.

What about insulin pumps?
Heat can make proteins like insulin harden, which increases the potential for infusion set occlusions (blockage). If you live in a hot climate and especially if you work outdoors, you may need to pay closer attention to how the heat can affect your insulin. A patient of mine, who is a roofer in Arizona, found that he needed to replace the insulin in his pump reservoir daily to avoid having high blood glucose readings. Using a pump wallet could be another option for people concerned about the effects of heat on their insulin. Also, make sure that the infusion set tubing is tucked in your clothing and not hanging out and exposed to the light and or heat.

Please share your stories.

Have a great week,


June 17, 2011