What medical conditions get worse with heat?

September 21, 2025 •

5 min read

According to the Centers for Disease Control and Prevention, extreme heat sends tens of thousands of people to the emergency room each year, with those with chronic conditions being especially vulnerable. Understanding what medical conditions get worse with heat is crucial for managing symptoms and preventing serious health complications during warmer months.

Quick Summary

Several chronic conditions, including cardiovascular disease, diabetes, and neurological disorders like Multiple Sclerosis, can be exacerbated by high temperatures, leading to worsened symptoms and increased health risks. This happens because heat places extra strain on the body's natural cooling mechanisms, and can also interfere with medications.

Key Points

Cardiovascular Risks: Extreme heat forces the heart to work harder, increasing the risk of heart attacks and irregular heartbeats in people with heart disease.
Neurological Flare-ups: For conditions like Multiple Sclerosis (MS), a rise in body temperature, even a minor one, can trigger temporary symptom flare-ups.
Diabetes Management: Heat can cause unpredictable fluctuations in blood sugar levels and can damage insulin and other diabetes-related equipment.
Respiratory Issues: High temperatures, along with poor air quality, can irritate the lungs and exacerbate conditions such as asthma and COPD.
Medication Effects: Many common medications, including those for mental health and heart disease, can impair the body's ability to cool itself or manage hydration effectively.
Dehydration Is a Major Factor: In all heat-sensitive conditions, dehydration is a primary risk that can worsen symptoms and place additional strain on vital organs like the heart and kidneys.

Why Does Heat Affect People with Chronic Conditions?

Extreme heat can put a tremendous strain on the human body, forcing it to work harder to maintain a stable internal temperature. The body cools itself primarily by sweating and by dilating blood vessels, which brings more blood to the skin's surface. For individuals with certain medical conditions, these processes can be compromised or place undue stress on their systems. Dehydration, electrolyte imbalances, and the interaction of heat with certain medications further complicate matters, making heat waves particularly dangerous for this vulnerable population.

Cardiovascular Disease

For those with cardiovascular disease, such as congestive heart failure, coronary artery disease, or hypertension, heat is a significant threat. When blood vessels dilate to cool the body, blood pressure can drop. To compensate, the heart has to pump faster and harder, which can strain an already compromised heart. Dehydration, which is common in hot weather, thickens the blood and makes the heart work even harder.

Increased Risk: Extreme heat increases the risk of heart attacks, heart arrhythmias, and other cardiovascular events.
Medication Impact: Some common heart medications, including diuretics and beta-blockers, can interfere with the body's ability to regulate temperature and fluid balance, compounding the risk.

Respiratory Conditions

High temperatures often go hand-in-hand with poor air quality, creating a dangerous combination for individuals with respiratory conditions like asthma and chronic obstructive pulmonary disease (COPD).

Air Pollution: Heat can increase ground-level ozone and other air pollutants that irritate the airways.
Humidity: High humidity can make breathing feel more difficult and heavier.
Dehydration: Staying properly hydrated is important for thinning mucus and keeping airways clear, and dehydration can worsen symptoms.

Neurological Disorders

Neurological conditions can significantly impact the body's ability to regulate temperature. A prime example is Multiple Sclerosis (MS), where even a slight rise in body temperature can cause a temporary worsening of symptoms.

Multiple Sclerosis (MS): This phenomenon, known as Uhthoff's phenomenon, can cause increased fatigue, weakness, vision problems, and other symptoms.
Parkinson's Disease: People with Parkinson's may have impaired sweating, which reduces their body's ability to cool itself effectively.

Diabetes

Managing diabetes in the heat can be a balancing act. High temperatures can affect both blood sugar levels and the stability of diabetes medications and equipment.

Blood Sugar Fluctuation: Heat can cause blood glucose levels to fluctuate unexpectedly.
Dehydration Risk: Dehydration can raise blood glucose levels.
Equipment Sensitivity: Insulin and glucose monitors are sensitive to heat and can be damaged if not stored properly.
Tips for Diabetics in Heat:
1. Test blood sugar levels more frequently.
2. Carry medical supplies in a cool bag.
3. Stay vigilant for symptoms of heat exhaustion, which can be mistaken for hypoglycemia.
4. Ensure proper hydration with water and electrolyte drinks, as recommended by a doctor.
5. Avoid strenuous activity during the hottest parts of the day.

Mental Health Conditions

Extreme heat can have a profound impact on mental well-being, potentially exacerbating symptoms of conditions like depression and anxiety. This connection is not fully understood but may be linked to sleep disruption, discomfort, and the side effects of psychiatric medications.

Medication Effects: Certain antipsychotic and antidepressant medications can affect thermoregulation or reduce thirst, increasing the risk of overheating.
Behavioral Impact: Heat can cause irritability and stress, which can worsen mood disorders.

Other Conditions Aggravated by Heat

Beyond the major chronic illnesses, several other conditions can flare up or be worsened by hot weather.

Arthritis: Hot, humid weather can sometimes increase joint pain and stiffness in people with arthritis.
Fibromyalgia: Many with fibromyalgia report that heat, especially with high humidity, worsens their headaches, muscle pain, and fatigue.
Lupus: Direct sun and heat exposure can trigger debilitating lupus flares, causing fatigue, joint pain, and rashes.
Kidney Disease: The kidneys work harder in hot weather, and dehydration from heat can worsen kidney function, especially for those with existing kidney disease.

Heat Sensitivity Risks: A Comparison Table


Condition	Primary Heat-Related Risk	Worsening Symptoms	Management Tips
Cardiovascular Disease	Increased strain on the heart	Low blood pressure, arrhythmias, heart attacks	Avoid strenuous activity; stay hydrated; consult doctor about meds
Respiratory Conditions	Poor air quality and humidity	Asthma attacks, shortness of breath	Limit outdoor time; use AC; stay hydrated
Multiple Sclerosis	Compromised thermoregulation	Fatigue, vision problems, weakness	Stay in cool environments; use cooling vests; avoid hot baths
Diabetes	Dehydration and medication damage	Blood sugar fluctuations	Monitor blood sugar closely; protect medications; stay hydrated
Mental Health Conditions	Medication side effects, stress	Anxiety, depression, irritability	Stay cool; maintain routine; consult doctor about meds
Lupus	UV light and general heat	Joint pain, fatigue, rashes	Limit sun exposure; use sunscreen; stay cool
Kidney Disease	Dehydration	Impaired kidney function	Maintain hydration levels; avoid NSAIDs; consult doctor

Protecting Yourself in the Heat

For those with conditions that get worse with heat, taking proactive measures is essential. The Centers for Disease Control and Prevention (CDC) offers many useful tips to prevent heat-related illnesses. Consider the following:

Stay in Air-Conditioning: Spend time in air-conditioned environments, such as your home, a public library, or a shopping mall, during the hottest part of the day.
Stay Hydrated: Drink plenty of fluids, preferably water, throughout the day. Avoid sugary drinks and alcohol, which can cause dehydration.
Dress Appropriately: Wear loose-fitting, lightweight, and light-colored clothing. A wide-brimmed hat can provide additional protection from the sun.
Plan Ahead: Schedule outdoor activities for the coolest times of the day, typically early morning or late evening.
Monitor Yourself: Pay close attention to your body's signals and know the signs of heat exhaustion and heatstroke.
Consult Your Doctor: Talk to your healthcare provider about how your specific condition and medications may be affected by hot weather.

For more detailed guidance on heat safety, you can visit the official CDC website and check their resources on heat and chronic conditions.

Conclusion

Heat is more than just an inconvenience for millions of people with chronic illnesses; it is a serious health risk. By understanding which medical conditions are aggravated by high temperatures and taking appropriate precautions, individuals can significantly reduce their risk of complications. Proactive management, careful planning, and communication with healthcare providers are key to staying safe and healthy during hot weather.

Frequently Asked Questions

Many chronic conditions worsen in the heat, including cardiovascular diseases (heart failure, hypertension), respiratory illnesses (asthma, COPD), neurological disorders (MS, Parkinson's), diabetes, mental health conditions, and autoimmune diseases like lupus.

A temporary worsening of MS symptoms due to heat is called Uhthoff's phenomenon. It occurs because heat slows nerve impulses, which are already damaged by the disease. Symptoms typically improve once the body cools down.

Yes, heat can cause blood sugar levels to rise or fall unpredictably. Dehydration from heat can increase blood glucose, while changes in activity can also cause fluctuations. Insulin and testing strips can also be damaged by high temperatures.

People with heart conditions should limit strenuous activity, stay in air-conditioned environments, and drink plenty of water. They should also consult their doctor about how their medications might affect their heat tolerance.

Common signs include feeling dizzy, lightheaded, or unusually thirsty in the heat. Medications such as diuretics, beta-blockers, and some psychiatric drugs can increase heat sensitivity. It is important to talk to your doctor or pharmacist if you are concerned.

Yes, studies show a correlation between extreme heat and an exacerbation of mental health symptoms, including increased anxiety and irritability. Certain psychiatric medications can also interfere with the body's cooling mechanisms, adding to the risk.

Signs of heat exhaustion include heavy sweating, cold/pale/clammy skin, dizziness, and nausea. Heatstroke is a medical emergency with symptoms like a high body temperature ($103^{\circ}F$ or higher), hot/red/dry skin, a rapid pulse, and confusion.

Seek out public, air-conditioned spaces like libraries, malls, or cooling centers. Take cool showers or baths and use cold towels on your skin. Use fans in cooler rooms and wear light, breathable clothing.