Domestic refrigerators may pose risk to insulin quality

New research being presented at this year’s European Association for the Study of Diabetes (EASD) Annual Meeting in Berlin, Germany (1-5 October), suggests that insulin is often stored at the wrong temperature in patients’ fridges at home, which could affect its potency.

Many injectable drugs and vaccines are highly sensitive to heat and cold and can perish if their temperature shifts a few degrees. To prevent loss of effectiveness, insulin must stay between 2-8°C/36-46°F in the refrigerator or 2-30°C/30-86°F when carried about the person in a pen or vial.

Individuals with diabetes often store insulin at home for several months before they use it, but little is known about how storage in domestic fridges impacts insulin quality.

To investigate how often insulin is stored outside the manufacturer’s recommended temperature range, Dr Katarina Braune from Charité - Universitaetsmedizin Berlin in Germany in collaboration with Professor Lutz Heinemann (Science & Co) and the digital health company MedAngel BV monitored the temperature of insulin formulations stored in fridges at home and carried as a spare.

Between November 2016 and February 2018, 388 diabetes patients living in the USA and the EU placed temperature sensors (MedAngel ONE, either next to their insulin in the fridge and or their diabetes bag.

Temperature data were automatically measured every 3 minutes (up to 480 times a day) before being sent to an app and recorded on a secure database. Temperature data were recorded for an average of 49 days.

Analysis of 400 temperature logs (230 for refrigerated and 170 carried insulin) revealed that 315 (79%) contained deviations from the recommended temperature range.

On average, insulin stored in the fridge was out of the recommended temperature range 11% of the time (equivalent to 2 hours and 34 mins a day). In contrast, insulin carried by patients was only outside recommendations for around 8 minutes a day.

Importantly, freezing was an even bigger issue, with 66 sensors (17%) measuring temperatures below 0?C (equivalent to 3 hours a month on average).

“Many people with diabetes are unwittingly storing their insulin wrong because of fluctuating temperatures in domestic refrigerators”, says Dr Braune.

“When storing your insulin in the fridge at home, always use a thermometer to check the temperature. Long-term storage conditions of insulin are known to have an impact on its blood-glucose lowering effect. 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 unnecessary variability in dosing. More research is needed to examine the extent to which temperature deviations during domestic storage affect insulin efficacy and patient outcomes.”

I’ve investigated the internal temps of literally dozens of fridges and yes they do vary quite a bit even within the same fridge throughout the day… and it doesn’t surprise me that many people’s insulin is spending time outside of the recommended range inside their own fridges. What I’ve seen no meaningful data on though, is how much it actually matters…

We’ve done a number of anecdotal experiments on FUD with insulin that’s been kept well outside of the recommended ranges, and we’ve yet to find an insulin that didn’t seem to work. But I’d be interested in seeing some actual laboratory data and controlled experiments to see under which conditions insulin actually starts losing effect, and how much


I think the effect of thermal lag needs to be considered in this discussion. Just because the internal temperature of a refrigerator fluctuates outside a desired range doesn’t mean the contents will experience the same degree of fluctuation. In my opinion, the only true test would be to put the sensor INSIDE the insulin bottle or a similar small liquid-filled container.)

Also, when a manufacturer states a temperature range for storage, that doesn’t imply to me that short excursions outside that range are harmful — only that continued storage over long periods will be detrimental.

If I go on a shopping trip that includes an insulin purchase, it could be 30 minutes or more before it goes in the refrigerator. So, it might be in a surrounding of 70 deg. F or more for that period. I don’t think that’s a problem.

IMHO - actually not.

When it comes to the FDA, my opinion (newly considered after reviewing the lengthy discussions on such over on FUD as mentioned by @Sam19 above) is that the manufacturer (and FDA approved) temperature range for storage is exactly what it says and nothing more. There are no implications.

If it says the product is stable for xxx days between xxx and xxx temperature range then that is exactly what it means and no more.

It does not state what happens outside that range and no assumption should (IMHO) be reasonably be made from what the manufacturer HAS stated (and had approved).

I follow Scott Strumello on Twitter, and he tweeted this morning about this: “Did pharma fund this research? The outcome suggests manufacturers are trying to shift blame away from themselves to patients for issues with the supply chain they control exclusively” – makes me wonder.


That’s an excellent thought to ponder… it seems pharma has enough trouble producing consistent insulin and would love to be able to blame it on supply chain and temps outside of their control. Check out this alarming summary on insulin consistency — and of course they blame it on the supply chain… but it makes me wonder too

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I’m not a professional, so I could be wrong about some of these things, but one thing that I would be more concerned about is not about how effective the insulin is when you take it out of the fridge, but how consistent that effectiveness is while you are using it. Many people use insulin pumps, so the insulin may be out of the fridge for 3, maybe even 4, days, and depending on many factors, including weather, activity, environment, etc. the temperature could have a wide range (near the frozen foods in the grocery store vs a walk in the hot sun). This inconsistency could make it harder to tweak your carb & basal rates. This is obviously helped by recent technologies such as Closed Loop Systems where you are not forced to use the same settings all the time, but consistent insulin effectiveness is still definitely important.

I believe (from memory so could be wrong) that most insulin is labeled (hence tested and FDA approved) for room temperature storage for 28 days from date of first opening.

Good afternoon. I haven’t stored my insulin in the fridge for some time. I keep it at room temperature and haven’t had a problem. I never have more then one vial that is used up and I don’t have an extra until 3 days before my next change. Maybe I’ve been lucky but it seems that this works for me. The insulin is kept in a cupboard away from anything that emits heat plus I keep my entire house at a reasonable temp., about 69-70 degrees. Wish I would have known about this research I would have applied. Not always up to date on things like that.

When I was first diagnosed with type 1 diabetes in 1966 they told us not to bother with refrigerating insulin since it didn’t make much difference to its potency.

If that’s true, we would need to be concerned with the multiple times we open the refrigerator door to stock the shelves or select items for meals and snacks. The compartment certainly goes higher than the recommended storage temperature and stays elevated for some minutes afterward.

After a trip to the grocery store, restocking the refrigerator is likely to take more than just a few minutes. This isn’t something I worry about, but with this strict interpretation of storage temperature, I’m certainly outside the limits.

I saw this thread and thought it would be a good time for another of my demos. I posted it on FUD, if you are interested in seeing it.

I hope this refrigerator nonsense is put to rest. Diabetics have enough to worry about, they don’t need to add worries that are not necessary.

Sure - keep it in the refrigerator, use it before the expiration date, follow all the recommendations, guidelines, and rules. There is nothing wrong with doing that.

But don’t worry needlessly if you occasionally go outside of the recommendations.

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Perhaps the the point I was attempting to make was misinterpreted.

The formulation of insulin in 1966 is very different from the insulin of today. I was DXD in 1964, and we kept it refrigerated in the summer.

I have noticed that when I take two bottles on 2 week trips, but using one and keeping the second as backup, that the second bottle after I get home is less potent. And I rarely refrigerate it, just keep it at room temperature, unless we are moving around a lot then I will keep it on ice. How much activity would it lose? Well I figure that it has to be over 20% to be noticeable. I doubt insulin left out of the refrigerator would lose all activity.

Regarding storage in you home refrigerator, it does depend where you store it in the refrigerator. I started taking Repath last year, and the package comes with a visual temperature sensor badge that changes color if the temperature goes up beyond the recommended storage range. I always kept my insulin in the egg compartment on the door of the refrigerator. What I noticed is that the temperature indicator would turn color after 1 week, and after 2 weeks would be at the second of three colors. After seeing that I started storing the insulin and Repath in a plastic box in the bottom shelf against the inside corner. The Repath color does not change after 2 weeks.

I think what is more important is how is the insulin shipped and stored by the pharmacy chain. There is no way to control for that. I wish the insulin manufacturers would incorporate the temperature indicator badge. So don’t be so quick to blame the manufacturer, they have no control over the middle man.

How do you tell that your insulin is losing potency? My basels are well controlled and if I notice that my basel bg is higher, or my post prandals are higher than expected, then I suspect my insulin may have lost activity (assuming I am in my usual routine and not coming down with something. BTW, I am in range 90-93% and my last A1c was 6.2.


I keep my insulin in the butter compartment. In there, there is ZERO RISK of the insulin getting near freezing temps. When I go to a hotel I NEVER USE the mini fridges as their temp management is worse than awful. Those things can easily end up freezing your insulin. Better to leave the insulin at room temp than to use one of those little fridges. I leave my working bottle of insulin at room temp at home anyway, so there’s no additional concern about temperature when I’m at a hotel.

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I’ve had that happen - that wasn’t a good day.

One of these days I’m going to look into purchasing the product @Terry4 spoke about in this post:

I think the largest threat with insulin temperature is freezing. I’m here to tell you that frozen insulin will no longer do the job. I suspect that raising the ambient temperature above the recommended range does not damage the insulin as quickly as freezing.

I, too, wonder is Big Pharma is trying to evade responsibility for possible manufacturing and quality control errors. If true, this adds insult to the injury of outrageously priced products.

One thing to consider is that we wear 3 days worth of insulin on our person, in a casing or on a clip, but close to our body which is almost 98.6 degrees. On a warm day, like Summer, it is significantly warmer. Yet the insulin still holds up. I would be more concerned about excursions to the low side in a refrigerator, which I have been told is freezing. Anything above the freezing temp is okay. As far as the high side, it would require detailed quantitative research to learn the relationship of temperature to insulin life.