Domestic refrigeration may pose an underestimated risk for insulin quality, according to study results presented at the 2018 European Association for the Study of Diabetes Annual Meeting held October 1-5 in Berlin, Germany.

Researchers sought to investigate how patients with diabetes handle and store insulin in their daily lives. The study objective was to monitor temperatures of refrigerated and carried insulin in developed countries to investigate how often storage conditions do not meet manufacturers’ recommendations for temperature range.

Investigators gave a total of 400 temperature monitors to 338 patients with diabetes in the United States (46%) and countries in the European Union (41%). Patients kept their temperature monitors alongside their insulin; 230 monitors tracked refrigerated insulin and 170 tracked carried insulin. Monitors measured environmental temperatures every 3 minutes up to 480 measurements/day and transmitted the data to an app, where it was stored on a protected online database. 

When the temperature recorded was outside of the recommended range (2 to 8°C for refrigeration and 2 to 30°C when opened or carried as a spare), patients were notified by an alarm. Data was collected between November 2016 and February 2018 with an average length of protocol of 49 days.

Deviations from the recommended storage temperatures were found in 315 (78.8%) of monitor logs. All 230 refrigerator monitor logs recorded deviations and 85 (50%) deviations were recorded in carried insulin logs. Refrigerated insulin was found to be outside of the recommended temperature levels an average of 11.31% of the time (2 hours 43 minutes/day). Carried insulin, however, was only found to be outside of the recommended temperature range an average of 0.54% of the time or an average of 8 minutes/day. Overall, 16.5% of sensors (57 refrigerated and 9 carried monitors) logged temperatures below 0°C.

Long-term improper insulin storage conditions are known to have an impact on medication efficacy. Study data indicated that in a significant number of cases, “insulin was exposed to temperatures outside the recommended range, especially when refrigerated.” The investigators concluded that further systematic investigation is required to determine the extent to which temperature deviation affects insulin efficacy and patient outcomes.

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Braune K, Kraemer LA, Zayani A, Weinstein J, Heinemann L. Storage conditions of insulin in domestic refrigerators and carried by patients: Insulin is often outside recommended temperature range. Presented at: 2018 European Association for the Study of Diabetes Annual Meeting; October 1-5, 2018; Berlin, Germany. Abstract 891.