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There are actually several ways in which hot weather (dry or humid) can significantly affect your blood sugar levels, your insulin needs, and even your vials of insulin!

In fact, the impact of heat on a person with diabetes (and any container of insulin) can be severe enough to send you to the hospital in DKA or struggling with unexpected plummeting blood sugars.

In this article, we’ll look at the issue of heat and diabetes in dehydration, glucose metabolism, and critical insulin storage needs.

Diabetes & Heat

Heat, dehydration & high blood sugars

Whether it’s hot and humid or hot and dry, mild-to-severe heat and dehydration can easily spike your blood sugars by 50mg/dL or over 200 mg/dL if you become dehydrated.

Quite simply, when your body becomes dehydrated — which means there is inadequate fluid in your tissues and bloodstream — the glucose in your bloodstream becomes more concentrated. 

According to  Dr. Roberta Lee at Medicine Daily, 60 percent of your body weight is made of water! 75 percent of your muscle weight is water, and 85 percent of your brain. Water is critical to your body functioning fully and properly.

And It’s easy to drink too little water without being aware of it.

(you can learn more about how much water you should drink here on Diabetes Strong)

Just a little dehydration on a daily basis can easily keep your insulin needs higher than they might otherwise be.

Moderate dehydration, on the other hand — like spending all afternoon at a 4th of July parade in 95-degree heat — can send your blood sugar soaring when you haven’t even eaten and are active. Normally, you’d anticipate low blood sugars, but add a little dehydration and your blood sugar will spike rapidly.

Sunburns can affect your blood sugar, too

On those hot, hot days, everyone is at risk for a sunburn, too. What’s happening on a cellular level is intense damage to the cells of your skin. Like any other physical injury, a sunburn is stressful on the whole body and creates a great deal of inflammation

And then the body needs to manage that inflammation and heal. Along with healing comes other hormones, including cortisol, to help manage the inflammation. For people with diabetes, this results in temporary insulin resistance and higher blood sugar levels.

Fortunately, those higher blood sugars shouldn’t persist for more than a couple of days. The more severe the burn is, the more significant the effect on your blood sugars. You can talk to your healthcare team about making a slight increase in your background insulin needs to keep your blood sugars in your goal range, which in turn will improve your body’s ability to heal the burn.

And of course, next time, wear more sunscreen!

How to prevent high blood sugars in the heat

First of all, when you’re outside on particularly hot days, remember to check your blood sugar regularly.

You can’t anticipate dehydration and high blood sugars because taking extra insulin prior to being dehydrated could easily lead to hypoglycemia.

The better approach is to try and avoid dehydration by drinking plenty of water and checking your blood sugar frequently when you’re in hot conditions.

For mild to moderate dehydration, you’ll want to get out of the heat, chug some water, and take a carefully calculated correction dose of insulin using your correction factor.  It can be tempting to take a larger than normal correction dose of insulin, but this can lead to a rapidly plummeting low blood sugar.

Remember, part of the high blood sugar is simply concentrated glucose because there isn’t enough water in your bloodstream. Part of what will bring it down — in addition to insulin — is simply drinking water and rehydrating. That’s why you should resist taking a “rage bolus” of insulin to correct the high.

In the future, when you’re hanging out in hot temperatures, drinking plenty of water should be one of your diabetes management priorities!

Heat and low blood sugars

As usual, diabetes management is never simple. Sometimes, those hot, hot summer days can enable your body to burn glucose far more quickly than usual.

Much like the slow and steady burn of glucose during a steady walk, your body is burning extra glucose while trying to keep your body cool.

Exercising on a hot, humid day — when you are properly hydrated — can easily result in low blood sugars despite doing everything you’d normally do during that work to prevent lows. 

While research has shown that your body works harder to stay warm in cold weather compared to cooling off in hot weather, there’s still an increased caloric burn that could result in burning more glucose, too. 

Unfortunately, it’s very hard to predict to what extent of hot weather might lead to a low blood sugar because of other factors — like what you last ate, insulin on-board, activity level, hydration level, and current blood sugar level.

Even variables like your menstrual cycle could lead to an entirely different blood sugar response while exercising in 90-degree weather one week versus another week.

How to fix prevent low blood sugars when it’s hot

Quite simply, the trick is to be prepared

Check your blood sugar often, keep fast-acting carbohydrates within reach at all times (especially when you’re exercising), stay hydrated to prevent spiking high, and then check your blood sugar again!

Heat and insulin

The ideal temperature for your insulin vials, pens, and the insulin in your pump is between 36 to 46 degrees Fahrenheit (2 to 8 degrees Celcius) but insulin vials or pens that are “in use” can be stored outside of the refrigerator at temperatures up to 86F (30C) for several weeks, as long as it isn’t exposed to too much direct sunlight.

When exposed for too long (even an hour) to extreme temperatures, your insulin will break down, sometimes to the point of being essentially useless for managing your blood sugar.

(Insulin also begins to break down the moment you open a vial or pen, which is why its suggested use is within 28 days of opening.)

But you can run into trouble with hot temperatures in certain situations, like:

  • Leaving your insulin in the car on a warm or hot day
  • Wearing your pump too close to your skin (body heat) while exercising or in hot weather
  • Leaving your insulin sitting in direct sun on a hot day
  • Packing your insulin in your suitcase during air travel
  • Leaving your insulin in a bag, in the shade, on a really hot day
  • Leaving your insulin in a bag, at the beach, in the sun
  • Leaving your insulin close to a heating system or heating vent

You can learn more about the safe temperature range of insulin and how to see if your insulin has spoiled in our guide Does Insulin Expire? Storage, Safety, and How to Tell If Your Insulin Has Gone Bad

How to keep your insulin cool

You can’t fix insulin that has been destroyed by the heat, but you can definitely prevent it from happening in the first place. 

First of all, just like your dog and your baby, you should never leave your insulin in the car. The interior of a car heats up quickly and easily when it’s parked and locked up with closed windows.

If you must leave your insulin in the car, it needs to be protected by some type of cooling product. Luckily, there are a lot of good options available:

FRIO cooling cases

The “Frio Pack” is designed specifically to protect insulin pens and vials from extreme temperatures.

It requires zero refrigeration. Instead, it is activated by immersing the pack in water for just a couple of minutes. Pat it dry quickly with a towel, put your insulin inside, and it will protect your insulin for up to two days before needing to be “reactivated” with more water. 

Buy FRIO cooling cases on their website (use code DiabetesStrong for a 10% discount)

You can see how it works in this video:

4AllFamily insulin travel cooler

If you are traveling and need to keep your insulin cool for extended periods, you can also use the 4AllFamily insulin travel cooler. Its 900ml volume will protect 6-8 insulin vials or pens without freezing your medicine.

It promises to keep your insulin cool for a maximum of 72 hours and is designed to be portable for on-the-go use.

You can also power it with a USB charger, which keeps your insulin cool indefinitely (as long as you have electricity).

Buy the 4AllFamily cooler on Amazon

You can see how it works in this video:

For more information on keeping your insulin cold, you can read our review of the best portable insulin fridges.

For those using an insulin pump, it’s important to avoid wearing your pump directly on your skin. Sometimes a pocket is further enough away from your body to prevent overheating.

For exercising (indoors or outdoors), it may be wise to purchase accessories designed to make wearing your pump easier, which in turn keeps it away from your body heat.

Being aware of heat as a person with diabetes

Like many aspects of living with diabetes, heat is one of those things we have to be on the lookout for constantly. Hot weather. Dehydration. High blood sugars. Low blood sugars. Destroyed insulin.

Personally, if I know I’m going to be running a lot of errands and I don’t want to keep my diabetes kit with me the whole time, I simply bring a little lunch box with an ice pack in it. 

And every July 4th, I’m on the lookout for dehydration and blood sugars over 300 mg/dL because it happened to me once and I’ll never forget it!

It’s one more darn thing we need to be very conscious of as people with diabetes, and it’s very important.