Heat Exhaustion and Heatstroke Symptoms: What You Should Look Out For

Heat-related illness — also known as hyperthermia — happens when the body is exposed to heat and can’t cool itself down. This includes heat exhaustion and heatstroke, which causes 1,000 deaths in the U.S. every year. But these are preventable conditions. If caught on time, quick treatment can save someone’s life, or prevent any long-term damage to vital organs. So everyone should know how to recognize heatstroke symptoms, and what to do when it happens. 

Heatstroke vs. heat exhaustion

Heatstroke and heat exhaustion are both heat-related illnesses, but heatstroke is more serious. 

Heat exhaustion:

• Has milder symptoms, like headache and nausea

• Is easier to treat, and doesn’t always need emergency medical care

• Can progress to heatstroke if not treated

Heatstroke:

• Has more serious symptoms, and typically involves a change in someone’s mental state

• Needs emergency medical treatment

• Can result in death or serious health issues

The main way to tell the difference between heatstroke and heat exhaustion is by someone’s symptoms.

Hyperthermia symptoms

Hyperthermia often starts when someone is in a warm environment and starts to get dehydrated. Some of the first symptoms of heat exhaustion or heatstroke might be:  

• Thirst

• Less urination

• Dry mouth

• Fatigue

But if your symptoms feel more severe than this, it could be a sign of a more serious heat-related illness. 

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Signs and symptoms of heat exhaustion

Common symptoms of heat exhaustion include:

• Muscle cramping

• Heavy sweating, which can feel like cold or clammy skin

• Pale skin color

• Nausea or vomiting

• Faster and weaker pulse than usual

• Fatigue 

• Headache

• Feeling weak, dizzy, or lightheaded

Signs and symptoms of heatstroke

Heatstroke shares a lot of the same symptoms with heat exhaustion. But if someone has any of these additional symptoms, they may be experiencing a heatstroke: 

• Hot, dry, red skin

• Body temperature of 103°F (39.4°C) or higher

• Confusion

• Loss of consciousness

• Seizure

Causes of heatstroke

The body usually cools itself by sweating, but sometimes that’s not enough. Some conditions, for example, can make it more challenging to regulate the body’s temperature.

These factors can place you at greater risk for heat-related illness:

• Environmental factors (hot temperatures, high humidity levels)

• Exercising or working in the heat

• Increased body weight

• Certain medical conditions, like heart disease, lung disease, high blood pressure, and  diabetes

• Conditions that affect thinking and mental health, such as dementia and or psychosis

• Heart medications, such as diuretics and beta blockers

• Psychiatric medications, such as antipsychotics and amphetamines

• Any recent vomiting or diarrhea, which can easily make you dehydrated

• Being younger than 4 years or older than 65 years 

Treatment for hyperthermia

Heat-related illnesses are serious. If you think someone has heat exhaustion or heatstroke, act quickly. Getting treatment as early as possible increases the likelihood a person will recover.

If you or someone near you is experiencing symptoms of heat exhaustion — or even just feeling overheated — you should:

• Stop all activity.

• Get into a cool environment, ideally indoors with air conditioning.

• Loosen clothing and remove extra layers.

• Cool the skin with ice packs, a moist cloth, or shower.

• Take sips of water.

But if someone has any symptoms of heatstroke — like confusion or lethargy — call 911 right away. And while you’re waiting for medical help to arrive, you can start to implement some of the first aid measures listed above. Just don’t try to force them to drink any water or take any medications. They could choke on this if they can’t swallow properly.

You should also get immediate medical help if your symptoms get worse or last longer than 1 hour.

How to prevent heat exhaustion and heatstroke

Overheating is more likely to occur when a person is dehydrated. This is because sweat is the body’s natural cooling system. Drink water and fluids with electrolytes before you become thirsty. By keeping up with fluids and staying hydrated, you’ll be able to sweat more. This will help to keep your body cool. 

Here are some tips for staying hydrated while in the heat:

• Drink 8 oz (1 cup) of water every 15 to 20 minutes.

• Try to drink fluids with electrolytes in them, rather than pure water.

• Don’t drink more than 48 oz (about 6 cups) of fluid per hour, to avoid a dangerously low salt level in the blood.

• Look at your urine color. If it’s light yellow, you’re well hydrated.

There are additional steps you can take to decrease the risk of heat-related illness. These include:

• Avoid being outdoors and exercising during the heat of the day.

• If you have to be outside, try to stay in the shade and avoid direct sunlight.

• Wear lightweight and light-colored clothing.

• Wear protective clothing (hat, pants, shirt, sunglasses).

• Avoid alcohol and caffeinated drinks.

• Eat salty foods.

• Be on the lookout for warning signs of heat-related symptoms.

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Written by:

Jewels Doskicz, RN, BA

Jewels Doskicz, RN, BA, is an Arizona-based registered nurse with 22 years of hospital-wide clinical nursing experience and 11 years of medical writing and editing experience. She was a former healthcare content creator for a digital health tool at HealthLoop and director of clinical content operations at GetWellNetwork.

Edited by:

Katie E. Golden, MD

Katie E. Golden, MD, is a board-certified emergency medicine physician and a medical editor at GoodRx.

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