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A new study published in Diabetes Technology & Therapeutics investigates storage conditions of insulin in household refrigerators and when carried by PwD. The surprising result: fridges at home might pose a risk to insulin quality.


This publication was the first study investigating insulin storage at home, in household fridges and carried by people with diabetes. Previous studies have raised concerns about insulin quality and have shown that domestic refrigerators are not always suitable for medication storage.

The study was co-authored by Dr Katarina Braune MD (Charité University Hospital, Germany), Prof Lutz Heinemann PhD (Science & Co, Germany) and MedAngel BV (The Netherlands).

The storage temperatures of both refrigerated and carried insulin were monitored with MedAngel temperature sensors. Surprisingly, insulin was more often stored too cold than it was exposed to heat. Household refrigerators are a more variable environment than assumed. People who store insulin at home are advised to frequently check on insulin storage temperatures with a thermometer to prevent their medications from freezing.


How do people store their insulin at home?

Insulin storage was investigated with 338 people with diabetes, most of them living in the US and the  EU. Data was collected through temperature sensors (MedAngel ONE), that were kept with the insulin either in a refrigerator or carried by the patient. The temperature data was then sent to an app and consequently stored in a protected online database.

Temperature was monitored for a time period of 49 days on average. In total, this accumulated to temperature data of over 53 years that was analyzed.


Insulin often exposed to freezing temperatures in the fridge

Insulin should be stored in the refrigerator (2–8°C/36–46°F) to keep best quality until expiration date. Once out of the fridge and in use or carried as a spare, it is good for a few weeks at room temperature, provided it is protected from heat (< 25°C/77°F or < 30°C/86°F).

The results for refrigerated insulin showed that, on average, insulin in the fridge was stored out of the recommended range 11 % of the time. This is equivalent to 1 day per month below 2°C/36°F and 2 days a month above 8°C/46°F.

In 1 out of 4 refrigerators, temperatures below 0°C/32°F were recorded. On average, refrigerated insulin was kept at freezing temperatures (below 0°C/32°F) for 3 hours per month. 

Surprisingly, when looking at the results for carried insulin, the results show that the time out of range makes up only 0.5 %.

When you think about insulin storage temperatures, people might first think about traveling and being out in the sun. However, insulin seems to be at higher risk in the fridge at home.

Temperature in fridges is not stable

A more detailed analysis of temperature profiles for fridges revealed a typical fluctuating pattern over time. Insulin package leaflets advise to ‘store in a refrigerator (2-8°C/36-46°F)’. These findings show that refrigerators often do not maintain this temperature range. This is in line with previous research on home storage of medications.

Insulin storage temperatures in three different refrigerators over a week
grey – in range (2-8°C/36-46°F), red – too warm (above 8°C/46°F), blue – too cold (below 2°C/36°F)

Due to fluctuations in fridge temperatures many people with diabetes might unknowingly be storing their medication at the wrong temperature in their fridge. This could affect insulin potency. 

Clinical impact of insulin storage still unclear

Storage conditions of insulin are known to have an impact on its blood glucose lowering effect. However, the extent of how temperature deviations in storage affect insulin potency and clinical outcomes needs further investigation.

Insulin is stable at room temperature for a few weeks, but should not be used when it was frozen. The FDA, for example, recommends for emergency situations, that insulin that has been exposed to heat might still be used with caution, but insulin that has been frozen should not be used under any circumstances.

It is not known, how frequent fluctuations below and above freezing point, as they were observed in household fridges in this study, affect insulin quality. Insulin manufacturers have not taken a statement on the study results yet.

Dr Braune, first author of the study and who lives with diabetes herself, stresses how important insulin quality is for daily blood sugar management:

“For people living with insulin-dependent diabetes who take insulin several times a day via injections or continuously administer insulin with a pump, precise dosing is essential to achieve optimal therapeutic outcomes. Even gradual loss of potency introduces variability in dosing, that simply is unnecessary.”


Regardless of potential clinical consequences, everyone should be able to rely on an unchanging quality level of their medications.


Considerations for People with Diabetes

There is no need to purchase a special medical refrigerator, but it is worth noting that often the recommended temperature range is not maintained in the fridge at home.

Often, the solution is simple: moving the medications to another shelf or adjusting the fridge settings. However, in order to find the right solution, people need to be aware of temperature deviations first.

Keeping a thermometer right next to insulin in the fridge shows which is the right placement and thermostat setting for an individual refrigerator.

There are several affordable types of thermometers available. Continuous temperature monitoring with alarms has proven to be most effective in capturing and preventing temperature excursions. Min-max thermometers, that capture fluctuations over the previous 24 hours, are widely used in clinical practice. When a simple thermometer is used, it is important to check it periodically over some hours, to get an accurate understanding of temperature progression.

Susan Weiner, registered dietitian-nutritionist and certified diabetes educator, told healthline.com  regarding this issue: “Getting a temperature sensor is a really fantastic idea.”


The full article can be found here: https://www.ncbi.nlm.nih.gov/pubmed/31009254