How Summer Heat Affects Your Glucose Levels (and What You Can Do About It)

Key Takeaways

• Summer heat can lead to glucose spikes and dips that make blood sugar regulation more challenging for people with diabetes.
• Dehydration can worsen glucose control and increase the risk of complications.
• Staying hydrated, protecting medications, monitoring devices, and planning for physical activity can help maintain stable glucose levels during hot weather.

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As summer heats up, many of us look forward to longer days, outdoor activities, and fresh seasonal foods. But for people with diabetes, the combination of heat, humidity, and altered habits can significantly impact glucose regulation, making it harder to maintain stable blood sugar levels.

From hydration to insulin effectiveness, summer introduces unique variables that require thoughtful adjustments to your routine. In this article, we’ll explore how the summer heat affects glucose levels and share practical, evidence-based strategies to help you stay in control.

How Heat Impacts Blood Sugar

Warm weather can lead to both glucose spikes and drops. Elevated temperatures can temporarily raise blood sugar levels due to the stress heat places on the body. High blood sugar can also increase how often you need to use the bathroom, which can further increase the risk of dehydration.

Heat and blood sugar are also related, as high temps can also impact how your body uses insulin, making it harder to predict blood sugar levels. Compounding these risks, diabetes-related complications such as nerve and blood vessel damage can impair your sweat glands, making it harder for your body to cool itself. 

Why Hydration Matters for Glucose Control

Staying hydrated is a crucial part of managing blood sugar levels. When you don’t drink enough water, your blood becomes more concentrated, which can lead to higher glucose levels (hyperglycemia). Certain medications given to people with diabetes, like GLP-1 agonists like Monjouro or Zepbound, can also suppress thirst and increase the risk of dehydration.

Dehydration creates a vicious cycle: high blood sugar prompts your body to try to flush out excess glucose through urine, which further depletes your fluids. Over time, this can make it even harder to maintain healthy glucose levels. Hormones like vasopressin help regulate the body’s fluid balance, but when these systems are thrown off by dehydration, glucose control becomes even more challenging.

The importance of hydration and blood sugar is clearly shown in research. Studies show that people who stay well hydrated tend to have lower fasting blood sugar and are at reduced risk of developing diabetes.  Even mild dehydration can raise blood sugar, as seen in studies on people with diabetes who had worse glucose responses when water intake was restricted. Drinking enough water becomes even more important when it’s hot outside, as you lose a significant amount of water through sweat and are at a higher risk of dehydration.

Heat Affects Medication and Monitoring

High temperatures also pose challenges for medications and monitoring devices, as heat exposure can reduce their effectiveness. Insulin is sensitive to heat and can begin to break down when exposed to high temperatures.  This degradation renders the insulin less effective, thereby increasing the risk of elevated blood sugar levels and impaired glucose control. Additionally, when used in hot conditions, insulin may be absorbed more rapidly from the injection site, potentially increasing the risk of hypoglycemia. 

Heat can also compromise the accuracy and function of essential diabetes tools, including continuous glucose monitors (CGMs), test strips, and blood glucose meters. Prolonged exposure to high temperatures can lead to malfunctions or false readings, issues that can interfere with making safe and timely decisions about food, medication, or activity. 

Increased Risk of Heat Illness and Its Effect on Blood Sugar

Heat-related illnesses (heat exhaustion or heat stroke) strain the body’s systems and directly impact glucose regulation. When the body overheats, it responds by sweating to cool down, resulting in fluid and electrolyte losses. These shifts can contribute to dehydration and trigger fluctuations in blood glucose levels.

People with diabetes are particularly vulnerable and are more likely to experience heat-related complications and face a higher risk of hospitalization during heat waves. Impaired thermoregulation, altered thirst perception, and co-existing conditions like cardiovascular disease can all amplify the danger. In addition, certain diabetes medications (such as diuretics, sulfonylureas, or SGLT2 inhibitors) may further increase susceptibility to dehydration or heat illness.

Practical Strategies to Maintain Stable Glucose in Hot Weather

Having diabetes doesn’t mean you can’t enjoy hot summer days. Here are evidence-based strategies to help manage glucose levels and reduce heat-related risks:

• Monitor More Often: Use a continuous glucose monitor (CGM) or test your blood sugar more frequently, especially when spending time outside during heat waves. Heat, hydration, and changes in your routine can cause significant highs and lows, so regular monitoring helps you stay ahead of any potential issues..

• Stay Hydrated: Even mild dehydration can disrupt blood sugar regulation, so drink water consistently throughout the day, even if you don’t feel thirsty. If you’re active or sweating heavily, consider low-calorie electrolyte beverages to replenish the minerals you've lost. However, avoid sugary drinks or those high in caffeine, as they can exacerbate dehydration.
• Protect Your Medications and Devices: Heat can degrade insulin and damage essential diabetes tools like CGMs, test strips, and blood glucose meters. Store medications and devices in insulated coolers or temperature-controlled environments. Avoid leaving them in hot cars, direct sunlight, or unshaded areas, such as beach bags.
• Be Strategic About Physical Activity: Exercise can lower blood sugar, but heat adds another layer of complexity. Plan outdoor workouts for early mornings or evenings when it’s cooler, and always carry fast-acting carbohydrates, like glucose tablets or fruit snacks, to quickly address hypoglycemia if it occurs.
• Dress for the Weather: Wear lightweight, loose-fitting, and light-colored clothing to help your body stay cool and regulate your body temperature. A wide-brimmed hat and broad-spectrum sunscreen are also helpful tools for protecting your skin and reducing the risk of overheating.
• Choose Hydrating, Low-GI Summer Foods: Snack on water-rich, low-glycemic index (GI) foods like watermelon, cucumber, and leafy greens in your meals. These foods not only help keep you hydrated but also support more stable blood sugar levels.
• Consult Your Healthcare Provider: Discuss the impact of hot weather on your diabetes management with your healthcare provider to determine if adjustments to your insulin or medication doses are necessary. Personalized advice can help you stay safe and in control.

The Bottom Line

Heat affects glucose levels in multiple ways, including dehydration, altered insulin effectiveness, and increased risk of heat-related illnesses. Staying hydrated, monitoring your blood sugar more frequently, and protecting your medications and medical devices are essential for managing blood sugar during the summer. Work with your healthcare provider to create a plan that allows you to enjoy the summer while keeping your diabetes management on track.

Learn More With Signos’ Expert Advice

Signos offers tools and resources designed to empower you with a deeper understanding of glucose levels. By offering personalized insights, Signos helps you make informed lifestyle choices tailored specifically to your body's unique needs. Whether you're looking to optimize your diet, enhance your fitness routine, or gain better control over your health, Signos equips you with the knowledge and support to take action. Learn more about how Signos can improve your health by exploring the blog.