Diabetes requires careful management, but high temperatures introduce unique challenges that destabilize blood sugar control and increase health risks. Heat affects the body’s ability to regulate its core temperature and changes how medications work, requiring individuals to be vigilant during warm weather. Understanding these biological mechanisms is the first step in creating a proactive safety strategy to minimize the danger of heat-related illness.
Increased Vulnerability to Heat Stress
People managing diabetes face a heightened risk of heat-related illness because the condition compromises the body’s natural cooling systems. One significant factor is diabetic neuropathy, which is nerve damage affecting the autonomic nervous system. This damage often impairs the function of sweat glands, particularly in the extremities, reducing the body’s capacity to cool itself through evaporation. Reduced sweating means body heat is retained, leading to a faster rise in core temperature.
The second major vulnerability stems from the relationship between high blood sugar and fluid loss. When blood glucose levels are elevated, the kidneys attempt to flush the excess sugar out through increased urination, a process known as osmotic diuresis. This causes rapid fluid depletion, meaning people with diabetes become dehydrated more quickly. The resulting dehydration concentrates the glucose in the bloodstream, driving blood sugar levels higher and creating a dangerous cycle. Certain medications, such as diuretics, can also contribute to this dehydration risk.
Heat’s Effect on Glucose Management
The metabolic changes induced by heat can cause blood sugar levels to swing in both directions, presenting a dual risk of low and high glucose. Heat exposure can increase the rate at which injected insulin is absorbed into the bloodstream. This occurs because high temperatures cause blood vessels to dilate near the skin’s surface, speeding up insulin circulation from the injection site. For individuals on insulin therapy, this accelerated absorption can lead to unexpected hypoglycemia, or low blood sugar.
Conversely, heat can trigger hyperglycemia, or high blood sugar, when coupled with dehydration or physical stress. Dehydration raises the concentration of glucose in the blood, making it more difficult to lower levels. Furthermore, physical stressors like sunburn are interpreted by the body as an injury, triggering a stress response that releases hormones that raise blood sugar levels. High blood sugar combined with severe dehydration can escalate into life-threatening conditions like Hyperglycemic Hyperosmolar State (HHS) or Diabetic Ketoacidosis (DKA). To manage these rapid fluctuations, check blood sugar levels more frequently in hot weather, especially before and after physical activity.
Protecting Insulin and Medical Devices
High temperatures pose a direct threat to the effectiveness of diabetes medications and the reliability of monitoring equipment. Insulin is a protein sensitive to heat; prolonged exposure can cause it to degrade and lose potency. Unopened insulin should be kept refrigerated, typically between 2°C and 8°C (36°F and 46°F). Once opened, pens or vials should be stored at room temperature, generally below 25°C or 30°C (77°F to 86°F), and protected from direct sunlight or enclosed hot spaces.
Insulin should never be left in a hot vehicle, as car temperatures quickly exceed the safe threshold of 37°C (98.6°F) and render the medication ineffective. Heat can also compromise continuous glucose monitors (CGMs) and insulin pumps. The adhesive patches for CGMs and pump infusion sets may fail in extreme heat and humidity, causing the sensor or set to detach. For insulin pumps, the insulin in the reservoir must be changed more frequently, often after 72 hours, as the pump’s proximity to the body and ambient heat can cause the insulin to break down faster.
Essential Safety and Hydration Strategies
A proactive approach to hot weather is necessary to manage diabetes safely, starting with consistent hydration. Individuals should drink water constantly throughout the day, rather than waiting for thirst, which is often a late sign of dehydration. Avoid beverages containing alcohol, caffeine, and high amounts of sugar, as these promote fluid loss or cause unwanted blood glucose spikes. Low-calorie sports drinks can replenish lost electrolytes, but plain water should remain the primary source of hydration.
Timing outdoor activity is a major safety measure; exercise is best scheduled for the cooler hours of the early morning or late evening. When outside, wearing light-colored, loose-fitting clothing and seeking shade are effective ways to reduce heat absorption. Sunscreen with an SPF of 30 or higher should always be applied, as sunburn causes a stress response that raises blood sugar.
Recognizing the signs of heat-related illness is important. A person experiencing heavy sweating, dizziness, nausea, or clammy skin should immediately move to an air-conditioned space and drink fluids. Seek immediate medical attention if symptoms progress, as they can indicate a serious medical emergency like DKA or heat stroke.
Signs Requiring Immediate Medical Attention
Seek immediate medical attention if symptoms progress to:
- Confusion
- Hot and dry skin
- Persistent vomiting
- Blood sugar that remains high and unmanageable