Are You Storing Your Insulin Properly?

Domestic refrigerators may pose a risk to the quality of your insulin, experts warn

Temperature Gage Showing SpoilageTemperature matters. To prevent loss of effectiveness, it's important for insulin to stay between 36 to 46 degrees Fahrenheit in the refrigerator. (Photo: 123rf)

If you are on insulin for your diabetes, you know: it's common to store it at home for several months before using it.

Now, experts suggest you may want to pay close attention to the temperature it's stored at in your home refrigerator, as well as when you carry it. To prevent loss of effectiveness, it must stay between 36 to 46 degrees Fahrenheit in the refrigerator and 36 to 86 degrees F when carried about the person in a pen or vial, according to experts and recommendations.

In a new study, researchers found that does not always happen. They presented their findings at the European Association for the Study of Diabetes annual meeting in Berlin in early October.1

Led by Katarina Braune, MD, a researcher at Charite-Universitaetsmedizin in Berlin, the researchers asked 388 patients with diabetes to monitor the temperature of insulin stored in refrigerators at home or carried as a spare between November 2016 and February 2018.  The participants used a wireless temperature sensor provided for the study by MedAngel.

The data about temperature was measured every 3 minutes, up to 480 times daily, then sent to an app and recorded on a database, the researchers say. The data was recorded, on average, for 49 days.

When they analyzed 400 temperature logs, including 230 for insulin in the refrigerator and 170 for carried, they found that 315, or a whopping 79%, had deviations from the recommended temperature.

On average, the insulin in the refrigerator was out of range about 11% of the time, or about 2.5 hours daily. The insulin carried was only outside the recommended range for about 8 minutes daily.

Freezing was another problem, with 17% of the sensors, or 66 of them, finding temperatures below 32 degrees, or about 3 hours a month.

Researchers' Input

The researchers did not evaluate whether the insulin lost potency, or effects on the participants' blood sugars, but only whether it was maintained in the correct temperature range.

But it is well known that correct storage temperatures are crucial. "The reason that insulin should be kept at certain temperatures is that it can lose potency when it is stored too warm or cold," says Laura Kramer, another co-author and an employee of MedAngel BV. "If this is a total or gradual process depends on the severity of a temperature excursion, meaning how long it was stored at what temperature."

If insulin totally loses potency, it will, of course, lead to high blood sugar levels.  Even gradual loss of potency can lead to problems, Kramer says.

Second Opinions

"I'm not surprised in the least by the results," says Elena Christofides, MD, FACE, the chief executive officer of Endocrinology Associates in Columbus, Ohio. She reviewed the findings but did not take part in the study.

She says she has suspected this has been going on. "I have several patients who are very sensitive to the efficacy of their insulin and after a period of time, it seems that their vials or pens go 'off,''' she says. "We give them a vial of ours kept at precise [temperature and storage] conditions and the insulin works again."

Another issue, she says, is that some patients hoard insulin, and "I worry even more about loss of control as the insulin degrades the longer it sits in the fridge," Dr. Christofides says.

The observation about improper temperatures for stored insulin ''is a part of the broad list of things that can cause a lack of control" in managing diabetes, says J. Michael Gonzalez-Campoy, MD, PhD, FACE, medical director and CEO of the Minnesota Center for Obesity, Metabolism, and Endocrinology in Eagan. He is an editorial board member of OnTrackDiabetes and reviewed the findings.

"Extremes of temperatures, such as freezing of the insulin, or boiling of the insulin, will change the structure of insulin and render it inactive," he says. While it is unlikely that insulin kept in a refrigerator will be exposed to the extremes of temperature that will degrade it, there may be a loss of potency, he says. ''And this may account for some of the variable control [of diabetes] seen periodically in patients with diabetes being treated with insulin."

He says more study is needed to find out if the storage conditions found in the study have an impact clinically or not—whether it actually can jeopardize your blood sugar control.

Practical Tips

To help keep insulin at proper temperatures, Kramer says people should be aware that home refrigerators have warm and cold zones. The colder zones, which should be avoided for insulin storage, are usually next to the freezer, at the bottom or the back wall, but can vary from model to model.

She also suggests using a thermometer kept right next to the medications to identify the best location for the insulin. If you have more than one refrigerator at home, store the insulin the one opened less often, she says.

Dr. Christofides is a consultant for Novo Nordisk, Eli Lilly and Chiasma and is on the speakers' bureau for Pfizer, Novo Nordisk, Eli Lilly, Boehringer Ingelheim, PamLab and Shire. Dr. Braune has no relevant disclosures. Ms. Kramer is a MedAngel BV employee.  Dr. Gonzalez-Campoy has no relevant disclosures.

Updated on: October 29, 2018
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