Heat Exhaustion

What is heat exhaustion?

Heat exhaustion is the most common type of heat-related illness. It can occur when you exercise or do manual labor in a hot environment, and your body struggles to cool itself down. When you have heat exhaustion, your internal (core) body temperature may be abnormally high, but it’s typically below 104 degrees Fahrenheit (40 degrees Celsius). You’ll likely sweat a lot and have other symptoms like dizziness, nausea and a headache.

Without treatment, heat exhaustion can turn into the most severe form of heat-related illness: heat stroke. A key difference between heat exhaustion and heat stroke is that with heat stroke, you have signs of brain dysfunction (encephalopathy). These include persistent confusion, changes in behavior (like aggression or agitation) and slurred speech. You’ll also have a dangerously high body temperature, typically above 104 degrees F.

If you or someone you’re with has signs of heat exhaustion or heat stroke, call 911 or your local emergency services number. Treating heat exhaustion is essential for preventing its progression to life-threatening heat stroke.

What are the signs and symptoms of heat exhaustion?

Heat exhaustion signs and symptoms include:

• Heavy sweating.
• Cold, clammy skin.
• Muscle cramps.
• Headache.
• Dizziness.
• Feeling tired or weak.
• Feeling thirsty.
• Nausea or vomiting.
• Fast heart rate (tachycardia).
• Fast and weak pulse (“thready pulse”).
• Fast, deep breathing (hyperventilation).
• Elevated body temperature — typically 101 to 104 degrees F (38.3 to 40 degrees C).

What are the first signs of heat exhaustion?

Heat exhaustion can begin with one or more of the symptoms listed above. But the first thing you might notice is that you have muscle cramping or spasms. These are known as exercise-associated muscle cramps, or heat cramps. They usually occur in the muscle group you’re using most heavily — like your arms, legs or abs.

Heat cramps feel like a slow, painful tightening or contracting of your muscles that you can’t control. They might begin during physical activity or soon after you stop.

Heat cramps are often the first warning sign that you could develop heat exhaustion if you don’t cool down. If they occur, move to a cooler area and replenish your body with fluids, like electrolyte-enhanced water. You should also rest for two days before returning to heavy work or exercise in the heat.

What causes heat exhaustion?

Heat exhaustion occurs when your body loses too much water and/or sodium (a key electrolyte) through your sweat. Heavy manual labor or a strenuous workout in a hot environment are common activities that cause this to happen. When you’re sweating a lot, it can be hard to take in enough fluids and electrolytes to replenish what you’re losing.

What are the risk factors for heat exhaustion?

You may have an increased risk for heat exhaustion if you:

• Work outdoors in hot temperatures, especially with high humidity.
• Exercise or do athletic competitions in a hot environment.
• Do intense physical activity in the heat without slowly building up to it (for example, traveling somewhere that’s much hotter than where you live and hiking or rock climbing).
• Exert yourself in the heat while wearing heavy equipment or protective gear.
• Are over age 65 and do strenuous physical activity in the heat.

What happens to the body during heat exhaustion?

When you have heat exhaustion, your body has trouble cooling itself down. Your core body temperature typically rises, but it’s generally below 104 degrees F (unlike in heat stroke, where your temperature spikes higher than this).

With heat exhaustion, you’re aware of what’s going on and don’t have any persistent disruptions to your brain function. You might feel momentarily confused, but this feeling soon passes. Persistent confusion or changes to your mental state could signal heat stroke.

How is heat exhaustion diagnosed?

Paramedics or other emergency services personnel may be the first providers you speak with. They’ll talk to you about your symptoms and check your vital signs. Depending on your condition, they may take you to a hospital for further evaluation and treatment.

What is the treatment for heat exhaustion?

Heat exhaustion treatment involves cooling your body, hydrating and monitoring for signs of heat stroke.

Treatment often begins on-site, wherever heat exhaustion happens — this is because the faster you cool your body down, the better your chances of preventing a progression to heat stroke. But you should still call emergency services so a healthcare provider can check you and provide further care at a hospital, if needed.

If you have signs or symptoms of heat exhaustion, do these things right away:

• Call for medical help.
• Move to a cooler or shaded area.
• Loosen or remove excess clothes.
• Lie down with your legs elevated.
• Use any available means to cool your body — like fanning yourself or soaking towels in ice water and applying them to your skin.
• Slowly sip water or other fluids. But do NOT drink anything if you suspect you might have heat stroke. Wait until help arrives. People with heat stroke are at risk of inhaling fluids (aspiration), which can be dangerous.

When emergency services personnel arrive, they’ll immediately look for any signs of heat stroke. They may do things to cool you down, like fanning you after misting your skin with cool water. They may take you to a hospital so you can receive IV fluids or faster methods of cooling.

If your heat exhaustion progresses to heat stroke, you’ll need to stay a couple nights or longer at the hospital. Providers will give you further treatment and monitor your condition.

How can I prevent heat exhaustion?

Here are some tips for preventing heat exhaustion:

• Stay hydrated. This involves taking in enough fluids to support your daily needs plus drinking even more than usual when you’re active. Tips for staying hydrated include setting alerts on your phone to remind yourself to drink up and eating foods with a high water content. It’s also important to take in enough electrolytes.
• Limit physical activity in the heat. Whenever possible, plan your outdoor activities for cooler times during the day (like early morning). If you work in a hot environment, talk to your employer about ways to lower your risk of heat exhaustion — for example, by taking short, scheduled breaks.
• Let your body get used to the heat. Healthcare providers call this process acclimatizing. It means you slowly work up to more intense physical activity in the heat over a period of at least a couple weeks. Start with short sessions and gradually increase the duration and intensity. This can help if you’re training for an athletic event (where you can’t control the weather on the big day) or planning a trip somewhere warm.
• Dress for the occasion. Wear loose-fitting or vented clothes when working out to allow air to circulate against your skin. This helps sweat evaporate and cool your body.

Preventing heat exhaustion in children

If your child plays a sport, talk to their coach about what they’re doing to prevent and monitor for heat exhaustion. Even if they don’t play on a team, kids and teens may overdo it in the heat because they don’t recognize when they’ve pushed their bodies to their limits.

Talk to your child about the signs and symptoms of heat exhaustion and help them understand it’s OK (and necessary!) to take breaks to let their body recover.

How long does it take to recover from heat exhaustion?

Recovery from heat exhaustion depends on how quickly you get treatment and whether it turns into heat stroke. Your healthcare provider can tell you more about what to expect. In general, most people need at least one or two days to feel back to normal.

Many people who receive care at a hospital for heat exhaustion can safely go home after just a few hours. You’ll need to rest and rehydrate for at least 48 hours before returning to your usual level of physical activity.

What questions should I ask my healthcare provider?

As you recover from heat exhaustion, it may help to ask your provider:

• What activities should I avoid as I recover?
• How much water should I drink each day?
• What should I do to take in enough electrolytes?
• When can I return to my usual level of physical activity?
• How can I prevent this from happening in the future?

What are the 3 stages of heat exhaustion?

Heat exhaustion itself doesn’t have three stages, but it’s often considered the second stage of heat-related illness. The first stage, or warning sign, is heat cramps. If you stay in the heat or continue to exert yourself, you may develop heat exhaustion. And without treatment, heat exhaustion can worsen into heat stroke.