What Is Heat Exhaustion? MDs Explain Symptoms and Treatment

Heat exhaustion probably isn’t something you think all the time, especially when a day out in the sun can feel so good. But the condition can cause symptoms you don’t want to ignore, including dizziness, fainting, and low blood pressure upon standing — among other things. Heat related-illnesses, like heat exhaustion, can also develop into heat stroke, a potentially-life threatening medical condition.

All of this is important to keep in mind considering that “the number of people exposed to extreme heat is growing exponentially due to climate change in all world regions,” according to the World Health Organization (WHO). So, what is heat exhaustion and why are there so many warnings about the dangers of it? We tapped four emergency medicine physicians for more info.

Experts Featured in This Article:

Lewis Nelson, MD, is the chair of emergency medicine at Rutgers New Jersey Medical School.

Ali Jamehdor, DO, is an emergency medicine physician and medical director of the Weingart Foundation Emergency Department at Providence Saint John’s Health Center in Santa Monica, CA.

Henry Young, MD, is an emergency medicine physician at The Ohio State University Wexner Medical Center.

Michael Levine, MD, is an emergency medicine physician at UCLA Health.

What Is Heat Exhaustion?

Heat exhaustion is one of several conditions in a category known as heat-related illness. (Other heat-related illnesses include heat stroke, heat rash, and heat cramps, according to the Centers for Disease Control and Prevention (CDC).)

Heat exhaustion is the body’s response to losing a lot of water and salt, usually through sweating, per the CDC. “It’s a syndrome that, if you pay attention to it and you feel it coming on, you can mitigate it through cooling and hydration, and can quickly recover from it,” says Lewis Nelson, MD, chair of emergency medicine at Rutgers New Jersey Medical School. “But if you don’t pay attention to it and it progresses, it’s a true medical emergency.”

Heat exhaustion “is a very tricky thing, and it’s important to be aware of it,” says Ali Jamehdor, DO, emergency medicine physician and medical director of the Weingart Foundation Emergency Department at Providence Saint John’s Health Center in Santa Monica, CA.

Heat Exhaustion Symptoms

The CDC lists the following as common symptoms of heat exhaustion:

“If you notice you start feeling weak, or experience muscle cramps or dizziness, it is important to remove yourself from the heat and try to go to a cooler area,” says Henry Young, MD, emergency medicine physician at The Ohio State University Wexner Medical Center.

Heat Stroke vs. Heat Exhaustion

Heat stroke is the most serious form of heat-related illness and happens when the body can no longer control its temperature, Dr. Nelson says. When someone has heat stroke, their body temperature rises quickly, their sweating mechanism fails, and their body is not able to cool itself down, according to the CDC. “Your organs start to dysfunction and fail, and there is an alteration of your mental status,” Nelson says. People with heat stroke “can act bizarre and agitated, or may not be able to speak,” Dr. Jamehdor says.

Heat illness “exists on a spectrum,” points out Michael Levine, MD, an emergency medicine physician at UCLA Health. “If not properly addressed, heat exhaustion leads to heat stroke, which can be a fatal illness,” he says.

“Anyone with signs of a heat stroke should get medical attention,” Dr. Young tells PS.

How Long Does Heat Exhaustion Last?

There is no hard and fast rule for how long heat exhaustion will last. “It’s totally variable,” Dr. Levine says. If someone has mild heat illness and moves to a cooler place and rests, their symptoms “should not last long,” with someone feeling better as soon as 15 to 20 minutes after they cool off, per Dr. Young. However, recovery from heat exhaustion usually takes 24 to 48 hours, according to Mount Sinai.

Heat Exhaustion Treatment

Treatment for heat exhaustion is fairly straightforward, Dr. Nelson says. If you suspect that you or someone near you has heat exhaustion, he recommends doing the following:

“It’s best to remove the person from the source of heat and get them out of the hot environment,” Dr. Levine adds. While water is good in this situation, a drink with electrolytes, like a sports drink, can also help, per Dr. Young. “It is important to replace that fluid loss with either water or sports drinks,” he tells PS.

If someone starts to throw up, has symptoms that get worse, or symptoms last longer than an hour, Dr. Nelson says it’s time to seek medical care.

“Heat exhaustion can creep up on you and it can lead to a lot of serious issues,” Dr. Jamehdor tells PS. “But it is preventable.”

Korin Miller is a writer specializing in general wellness, health, and lifestyle trends. Her work has appeared in Women’s Health, Self, Health, Forbes, and more.