Heat and diabetes can be a dangerous combination

During heat waves, heat-related illnesses, like heat stroke or exhaustion, may come to mind. While dangerous, there are other health consequences that may be just as risky—but more common and lesser-known. In fact, heat can make it harder to manage diabetes, which affects tens of millions of people in the United States.

Complicating matters, many people with diabetes and prediabetes (the precursor to the disease) don’t even know they have it, while those who’ve been newly diagnosed may be still learning how to keep their condition under control. Those with diabetes who see heat as merely an uncomfortable nuisance may be more vulnerable to its harmful effects.

The body doesn’t work as well in extreme heat

Heat can worsen existing health issues, like heart, lung, and kidney disease because organs (including the brain) don’t work as well in these extreme conditions. As the body tries to release heat and cool down, blood is diverted from these essential organs to the skin. The body functions best within a narrow temperature range. NASA scientists suggest its upper threshold is a wet-bulb temperature of about 95° Fahrenheit.

Wet-bulb temperature is a measure of heat stress. It’s the lowest temperature to which an object can cool down through evaporation. The lower the wet-bulb temperature, the easier it is for people to cool off when it’s hot and humid.

NASA reports that wet-bulb temperatures are rising around the world. When exposed to high wet-bulb temperatures of 95° Fahrenheit for six hours or more, the body begins to lose its ability to cool down and the risk for heat-related problems increases. That’s concerning as climate change is making extreme weather events, like heat waves, not only more common but also more severe.

Those with type 1 or type 2 diabetes may feel the heat even more than those without the condition for a few reasons.

Sweat is a coping mechanism that helps the body cool itself. As the sweat dries on the skin, the evaporation has a cooling effect. But diabetes can damage blood vessels and nerves, which could prevent the sweat glands from producing sweat and cooling the body effectively. Humidity can make things even worse since it prevents sweat from evaporating as well, lessening its cooling effect and increasing the risk for heat-related medical emergencies, like heat stroke.

When people sweat, they lose water. People with diabetes also become dehydrated more quickly, which can cause their blood sugar level to rise. In turn, high blood sugar can cause people to urinate more, worsening dehydration. Some people with diabetes also take diuretics (water pills) to treat high blood pressure, which could also contribute to dehydration.

For those who rely on insulin to help keep their blood sugar levels under control, heat can make this more difficult. When people are dehydrated, the blood supply to their skin is reduced. This can not only hamper the body’s ability to release heat, but also interfere with its ability to absorb injected insulin.

Insulin, itself, is also vulnerable to extreme temperatures. It can usually remain stable at temperatures up to about 95° Fahrenheit. Beyond that, it can break down rapidly, rendering it less effective.

A July 2022 study published in Environment International Data examined daily hospitalizations from a nationwide database in Japan for blood sugar-related emergencies, including diabetic ketoacidosis or DKA (when the body doesn’t have enough insulin to carry sugar out of the blood and into cells), hyperosmolar hyperglycemic syndrome or HHS (very high blood sugar levels), and hypoglycemia (very low blood sugar levels) that occurred between 2012 and 2019. The researchers found that heat exposure increased the risk of hospitalization or death for each of these complications.

Diabetes rates are climbing in the U.S.

Over the past two decades, the number of U.S. adults diagnosed with diabetes has more than doubled. More than 37 million Americans have the disease and some 96 million have prediabetes (higher than normal blood sugar that has not yet progressed to diabetes). But 20 percent of those with diabetes aren’t aware that they have the condition, which is the 8th leading cause of death in the U.S. The same is true for more than 80 percent of those with prediabetes.

Increasing rates of the chronic disease are largely tied to the aging population and obesity, but emerging research suggests that people who recover from COVID also have a higher risk of developing diabetes.

A March 2022 study published in Diabetologia reviewed data on 8.8 million people across Germany from March 2020 through July 2021. The researchers compared 35,865 people who were diagnosed with COVID to a control group matched for age, sex, health issues, obesity, and other factors. The study found that those who recovered from COVID were 28 percent more likely to develop type 2 diabetes within three months. More follow-up is needed to understand if type 2 diabetes after mild COVID is temporary or a chronic health issue.

A separate April 2022 study of more than 27 million people in the United States published in PLOS ONE found those who were diagnosed with COVID were 42 percent more likely to develop type 1 diabetes than those who were not infected. The risk was highest among very young children and also higher among older adults. The researchers also noted differences across race and ethnicity. American Indian/Alaskan Native, Asian/Pacific Islander and Black people were more likely to be diagnosed than other groups.

Scientists are still working to understand if diabetes after COVID is temporary and will resolve in time or if it is a chronic health issue, but the fact that otherwise healthy people are being newly diagnosed with the condition could mean they are ill-prepared to handle lesser-known heat-related complications.

Tips to manage diabetes in the heat

There are several ways people with diabetes can protect their health and manage their condition in the heat, including:

Monitor your blood sugar more closely. Diabetes typically involves routine monitoring of blood sugar levels. But when temperatures soar, testing more often may be necessary, particularly before and after physical activity. It’s also wise to talk to your healthcare provider (HCP) about whether your medication needs to be adjusted.

Be mindful about medication storage. Insulin and glucagon are sensitive to extremely hot or freezing temperatures. Exposure to extreme heat or cold can make these hormones less effective. Insulin pumps as well as diabetes test strips and monitoring devices may also not work as intended in very hot conditions. Don’t store these medications or equipment in direct sunlight or in a parked car. When traveling, keep medications in a cooler, but avoid placing them directly on ice or an ice pack. For those who use an insulin pump, putting less insulin in the reservoir and refilling more often on hotter days can help ensure the medication’s potency. Putting the pump in your pocket or a case where it’s out of direct sunlight can also help.

Be prepared for blood sugar swings. Since heat can make it harder to control your blood sugar levels, it’s also important to keep snacks, sugar tabs, or gels on hand to treat low blood sugar.

Take steps to stay cool and hydrated. Drinking plenty of water—even before you feel very thirsty—is important. Avoid outdoor physical activity during peak sun hours, or between about 11:00 a.m. and 3:00 p.m. When temperatures soar, stay indoors in air conditioning either at home or in a public place. Wear a hat and sunscreen if you do go outside and opt for loose and light-colored clothing to keep your body temperature as cool as possible.

Protect your feet. Over time, diabetes can lead to nerve damage that can cause people to lose feeling in their feet. When the temperatures rise, outdoor pavement, stones, sidewalks, sand, and other walking surfaces can get very hot. Be sure to wear shoes and avoid going barefoot—even at the beach or pool—to prevent burns or other damage to your feet.