Heat exhaustion vs. heat stroke: Key differences and how to prevent heat-related illness

• Heat exhaustion comes before heat stroke and can cause weakness, lightheadedness, and nausea.
• Heat stroke requires medical attention, whereas heat exhaustion can be treated at home by cooling down the body.

Heat stroke and heat exhaustion are two types of heat-related illnesses. These conditions most commonly occur during physical exertion in hot and humid temperatures.

Heat exhaustion comes first, and if it's left untreated, it can lead to heat stroke — which may cause damage to vital organs or even be fatal. In fact, more than 600 Americans die of heat stroke every year.

It's important to understand the different symptoms and treatment methods for heat exhaustion and heat stroke, so you can take the appropriate action to prevent harm. Here's what you need to know.

Differences between heat exhaustion and heat stroke

To recognize the difference between heat stroke and heat exhaustion, it's important to look for changes in mental status.

According to Josh Scott, MD, primary care sports medicine physician at Cedars-Sinai Kerlan-Jobe Institute, someone suffering from heat exhaustion may feel light-headed and weak, but they'll be able to carry on a conversation. Someone suffering from heat stroke will be very confused and may even become unconscious.

There are also major differences when it comes to treatment. While heat exhaustion can be treated and managed at home, heat stroke requires a call to 911 and immediate medical attention.

Quick tip: If a person's cognitive ability seems to be altered, it's likely that they're experiencing heat stroke, not just heat exhaustion.

Heat exhaustion symptoms

The main symptoms of heat exhaustion are:

• Profuse sweating
• Rapid, weak pulse
• Clammy skin
• Nausea
• Heat cramps or muscle spasms
• Lightheadedness
• Shortness of breath

If you notice these symptoms, you should immediately seek shade or go indoors into air conditioning. You can also help lower your body temperature by drinking lots of water, applying cool, wet cloths while sitting in front of a fan, or submerging yourself in cold water.

Quick tip: It can take less than 30 minutes for heat exhaustion to escalate into heat stroke, so try to cool down immediately.

Heat stroke symptoms

If you don't cool yourself down, heat exhaustion can progress into something more dangerous called heat stroke.

There are two main indicators of heat stroke that differentiate it from heat exhaustion: a core body temperature above 104°F and central nervous system dysfunction.

This can result in the following symptoms:

• Rapid, strong pulse
• Altered mental status, such as confusion, disorientation, or slurring of speech
• Possible loss of consciousness
• Red, flushed skin
• Vomiting

If someone is experiencing these symptoms, it's important to call 911 right away. If left untreated, heat stroke can damage vital organs like the brain, liver, or kidneys, and sometimes it is fatal.

In the meantime, you should cool the body down in the same way you would with heat exhaustion — submerging in cool water, drinking lots of cold water, and placing wet cloths while in front of a fan or air conditioner.

Heat exhaustion treatment

Heat exhaustion can be treated without medical intervention if caught in time. A few treatment options include:

• Get out of the heat and into cooler temperatures.
• Hydrate with water and electrolytes.
• Cool the body down with cool water, damp cloths, or ice packs.
• Loosen or remove tight clothing.

Heat stroke treatment

While heat stroke will require medical attention, there are a few ways to help someone suffering from heat stroke. These include:

• Submerging them in cool water.
• Placing ice packs or cool clothes around their armpits, groin, and neck.
• Removing unnecessary, tight clothing.

Quick tip: Call for medical attention immediately, and apply these treatment methods, if possible, in the meantime.

How to prevent heat exhaustion and heat stroke

To avoid heat stroke, you have to first prevent heat exhaustion. This can be done using the same precautionary measures for hot and humid temperatures.

Here are a few helpful tips that can keep you safe from both heat-related illnesses:

• Avoid the hottest part of the day. Temperatures are generally highest between 3 and 4:30 pm. If you do wish to exercise outside during the summer months, aim to exercise very early in the morning or late in the evening to avoid the sun and higher temperatures.
• Build up to exercise. If you are not acclimated to hot and humid conditions when exercising, don't jump right into it. "Gradually adjust to high temperatures by slowly increasing your exercise duration and intensity over a couple of weeks," says Elizabeth Barchi, MD, primary care sports medicine specialist at New York University Langone Sports Health.
• Have a plan. If you are going to be working or exercising outside in the heat, you should have an idea of how you will cool yourself down if you experience symptoms. Barchi recommends thinking through these questions: Is there a place to seek shade on your route? Do you have water with you? Are you able to step into an air-conditioned building? Can you call someone for help?
• Stay hydrated. Your body cools itself by sweating, and if you don't take in enough fluids, your body won't be able to regulate its temperature. Scott recommends taking a drink every 15 to 20 minutes while you work out.
• Wear loose-fitting clothing. Tight or excessive clothing can trap heat, so dress lightly and avoid layering.

Insider's takeaway

It's important to know the difference in symptoms and treatment for heat exhaustion and heat stroke — especially for those most at risk, such as young children and older adults.

Between 1999 and 2010, more than 8,000 heat-related deaths were reported in the US. Of those, about 36% were adults aged 65 and older.

During hot and humid temperatures, make sure that your loved ones are practicing these measures to prevent heat-related illness and understand what to do if symptoms occur.