By Robert Preidt
Insulin should be stored in a refrigerator at between 36 and 46 degrees Fahrenheit (2 to 8 degrees Celsius), and at 30 to 86 degrees F (2 to 30 degrees C) when carried by the patient in a pen or vial, the researchers said.
Even though diabetes patients often store insulin in fridges at home for several months before they use it, little is known about how this affects insulin quality, the researchers explained.
This study included 388 diabetes patients in the United States and Europe who placed temperature sensors next to their insulin in the fridge and/or their diabetes bag. The sensors measured temperatures every three minutes (up to 480 times a day), and data was collected for an average of 49 days.
An analysis of 400 temperature logs (230 for refrigerated and 170 for carried insulin) showed that 315 (79 percent) had deviations from the recommended temperature ranges.
On average, insulin stored in the fridge was out of the recommended temperature range 11 percent of the time (equal to 2 hours and 34 minutes a day), while insulin carried by patients was only outside recommendations for around 8 minutes a day.
Freezing was an even bigger problem, with 66 sensors (17 percent) recording temperatures below 32 degrees F (0 degrees C), equivalent to 3 hours a month on average, according to the study.
The findings were presented at the annual meeting of the European Association for the Study of Diabetes, which concluded Oct. 5 in Berlin. Such research is considered preliminary until published in a peer-reviewed journal.
"Many people with diabetes are unwittingly storing their insulin wrong because of fluctuating temperatures in domestic refrigerators," said study author Katarina Braune, who's with Charite - Universitaetsmedizin Berlin in Germany.
"When storing your insulin in the fridge at home, always use a thermometer to check the temperature," she advised in a meeting news release. "Long-term storage conditions of insulin are known to have an impact on its blood-glucose lowering effect."
"More research is needed to examine the extent to which temperature deviations during domestic storage affect insulin efficacy and patient outcomes," she concluded.