Heat Exhaustion: What It Is and What to Do About It

Medically Reviewed By Meredith Goodwin, MD, FAAFP
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Heat exhaustion occurs when the body’s temperature becomes excessively high. It can cause dizziness, confusion, and nausea. Common causes include strenuous physical activity, dehydration, and hot weather. Heat exhaustion is not usually a serious health concern. However, it can trigger heatstroke, a potentially life threatening condition that can damage your brain and other organs.

To lower your risk of heat exhaustion and heatstroke, drink plenty of water and take breaks from hot or strenuous activities.

This article will discuss heat exhaustion, including its symptoms, causes, and treatment.  

What is heat exhaustion?

A person rubs sweat off their forehead
Mauro Grigollo/Stocksy United

Heat exhaustion occurs when the body is unable to regulate its core temperature. It usually follows intense physical activity.

When you exert significant energy, your body expends its fluids as sweat. Sweat evaporates to cool the body, helping it to regulate its internal temperature.

However, if your body loses too much fluid, you may be unable to sweat and can become dehydrated. Dehydration, in turn, can cause heat exhaustion.

Heat cramps and heatstroke 

For many people, heat exhaustion starts as heat cramps.

Heat cramps are painful muscle spasms that result from excessive heat. They can cause heavy sweating, fatigue, and thirst.

Without treatment, heat cramps may progress to heat exhaustion and heatstroke.

Heatstroke is a serious heat illness that occurs when your core body temperature rises to 104°F or higher.

It can disrupt mental function and cause confusion, slurred speech, seizures, and other serious symptoms. Heatstroke can also cause heart, lung, kidney, and liver problems in severe cases.

What are the causes of heat exhaustion?

Hot environments and dehydration from intense physical activity are the most common causes of heat exhaustion. In these circumstances, your body can become unable to cool itself, and you can become ill.

Any situation that involves excessive temperatures can cause heat-related illness.

What are the symptoms of heat exhaustion?

In some people, symptoms of heat exhaustion appear suddenly. In others, symptoms develop over time.

The most common symptoms include:

Before symptoms of heat exhaustion appear, you may experience symptoms of heat cramps. These symptoms include a red rash and muscle cramps

Seek a cooler environment if you think you may have heat cramps or heat exhaustion. If your symptoms are severe or do not improve, seek medical care.

How do doctors diagnose heat exhaustion?

Doctors will need to ask you about your medical history and check your temperature to diagnose heat exhaustion. People with heat exhaustion will typically have a temperature of 100°F or higher.

Your doctor may also order some lab tests to rule out heatstroke and other possible illnesses. Blood tests can check for electrolyte levels in your blood, while urine tests can help doctors assess how well your kidneys are functioning.

What are the treatments for heat exhaustion?

You may be able to treat heat exhaustion with the right home remedies. These remedies can help rehydrate your body and restore your body’s ability to cool itself.

They include:

  • Drinking water in sips: When you drink enough water, your body can produce enough sweat to cool itself. 
  • Resting: Find a cool, shaded area and lie on your back with your legs slightly elevated.
  • Taking a bath: A cool bath may help lower your body’s core temperature. You can also apply cool towels to your skin.
  • Loosening clothing: Be sure to remove any excess or tight clothing to improve airflow around your body.

If your symptoms persist after these remedies, you may need medical treatment. Your doctor may administer IV fluids through your veins to reduce dehydration.

They may also try to lower your body’s temperature with an evaporation cooling technique. This technique involves fanning your body while spraying water over it to facilitate evaporative cooling.

What are some potential complications of heat exhaustion?

Without treatment, severe heat exhaustion can lead to heatstroke. This condition can have life threatening implications, including:

Be sure to get prompt and effective treatment to prevent these complications.

What are the risk factors for heat exhaustion?

The following factors can increase your risk of heat exhaustion:

  • Age: According to the Centers for Disease Control and Prevention (CDC), older adults are at an increased risk of heat exhaustion.
  • Alcohol: Alcohol has properties that can speed up dehydration.
  • Medications: Certain medications, such as for depression, insomnia, allergies, and blood pressure, can also dehydrate the body more quickly. 
  • Weight: Being overweight means you have higher water needs and are more likely to become dehydrated.

Other risk factors for heat exhaustion include:

Can you prevent heat exhaustion?

Heat exhaustion is largely preventable. The main preventive measures include staying hydrated and avoiding strenuous physical activity.

Other measures include:

  • wearing loose, light-colored clothing
  • avoiding the sun, especially in the hottest parts of the day
  • taking cool showers
  • avoiding alcohol

Frequently asked questions

These are a couple of commonly asked questions about heat exhaustion and related illnesses.

How long does heat exhaustion last? 

With treatment, symptoms of heat exhaustion usually go away within 30 minutes. If they last longer, seek medical treatment.

Is heat exhaustion different from heatstroke? 

Heat exhaustion and heatstroke are both heat-related illnesses, but they are not the same. Heat exhaustion is a mild illness that usually causes dizziness, confusion, and headache. On the other hand, heatstroke is a serious illness that can cause organ failure and brain damage.

Summary

Heat exhaustion is when the body’s temperature rises to very high levels. It commonly results from intense physical exercise, dehydration, and prolonged exposure to heat.

Doctors usually diagnose the illness by assessing your medical history and checking your temperature. If your temperature is 100°F or higher, you may have heat exhaustion.

In most people, heat exhaustion responds to home remedies. These remedies include drinking enough water, resting, and wearing loose clothing. 

Untreated heat exhaustion may lead to complications, such as heatstroke. Heatstroke is a serious condition that can cause organ failure and brain damage.

Seek prompt medical treatment if you have symptoms of severe heat exhaustion.

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Medical Reviewer: Meredith Goodwin, MD, FAAFP
Last Review Date: 2022 May 25
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THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
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