Heat Exhaustion vs. Heatstroke

Reviewed on 5/20/2022

What Is the Difference Between Heat Exhaustion and Heatstroke? Which Is More Serious?

Picture of a man wiping sweat off his head.
Picture of a man wiping sweat off his head.

Heat Exhaustion

Heat exhaustion and heatstroke are both a type of heat-related illness. Other types of heat illnesses include heat rash, heat cramps, and heat syncope (fainting). Heat exhaustion often occurs when people work or play in a hot, humid environment and body fluids are lost through sweating, which causes the body to overheat and become dehydrated. The temperature may be elevated, but not above 104 F (40 C).


Heatstroke (also called heatstroke or sunstroke) also is a heat-related illness, and it is a life-threatening medical condition. It usually develops because of untreated heat exhaustion. The body's cooling system, which is controlled by the brain, stops working and the internal body temperature rises to the point at which brain damage or damage to other internal organs may result (temperature may reach 105 F or greater [40.5 C or greater]). Heatstroke is a medical emergency.

Both heat-related illnesses are more dangerous when they happen in children or the elderly, or in people that have certain pre-existing health conditions.

If you think that you or someone with you is having a heatstroke, call 911 or go to the Emergency Department immediately because it can cause death. While waiting for emergency services to arrive use first aid treatments in this article because heatstroke can cause death.

What Are the Differences Between the Warning Signs and Symptoms of Heat Exhaustion vs. Heatstroke (Chart)?

Symptoms of heat exhaustion are milder than symptoms of heatstroke, which can be severe. The signs and symptoms of these heat-related illnesses may not always be apparent in children or the elderly.

Chart Comparing Heat Exhaustion vs. Heatstroke Symptoms and Signs
Heat Exhaustion Symptoms & Warning SignsHeatstroke Symptoms & Warning Signs
Pale, cool, clammy skinFlushed, hot, dry skin
Profuse sweatingThe person may no longer sweat due to dehydration.
Core body temperature usually is elevated to more than 100 F (37.7 C), but not above 104 F (40 C)Core body temperature is 105 F (40.5 C) or more.
Dizziness or lightheadednessFainting, confusion, coma
Blood pressure changes (may be high or low)
Hyperventilation (rapid breathing)

Which Heat Exhaustion and Heatstroke Signs and Symptoms Are the Same?

Heat exhaustion and heatstroke have similar symptoms, for example:

The difference is that heatstroke will progress beyond those symptoms to more severe symptoms that are a danger to your health. If heatstroke isn't treated, the person can die.

What Causes Heat Exhaustion vs. Heatstroke?

Heat exhaustion often happens when you work or play in humid, hot weather or other environment; and your body has not adjusted to the heat. Your body usually cools itself through sweating. When it is hot and humid, and you sweat excessively you can become dehydrated from the loss of essential fluids and salts (electrolytes).

If you have heat exhaustion and do not receive prompt treatment, heatstroke can occur because sweating can no longer cool your body. Moreover, heatstroke develops rapidly, and can lead to death if medical attention is not sought for treatment.

What Are First-Aid Treatments for Heat Exhaustion and Heatstroke?

Heat Exhaustion

Heat exhaustion treatment begins with treating dehydration by drinking cool (not ice cold) sports drinks (with 6% or less glucose), not plain water. If a you can't keep fluids down, a doctor or other health care professional may use intravenous (IV) fluid for rehydration. You'll need to rest in a cool environment for several days.


If you or someone you know is suffering from heatstroke, they need medical treatment immediately or they may die. There is no home treatment. A doctor or other health care professional may use immersion, evaporative, or invasive cooling techniques to reduce the patient's core body temperature. An IV is started to give fluids, and treatment will continue until the patient's core body temperature is about 101.3-102.2 F (38.5-39 C). Hospital admission may be necessary for further tests and observation. 

What Should You Do If You Think You Are Having Heat Exhaustion or Heatstroke?

If you think you or someone you know is suffering from heat exhaustion, call a doctor or healthcare provider, or get to an emergency department if you think the person has heatstroke.

Heatstroke is a life-threatening medical emergency. If you suspect heatstroke, call 911 or get to a hospital immediately.

Go to an emergency department right away if the person is unable to keep fluids down (vomiting) or if their mental status begins to deteriorate and there are symptoms of confusion or delirium. Shortness of breath, chest pain, or abdominal pain may be signs of additional medical problems.

Heat Cramps Symptoms and Signs

Heat cramps are brief, painful muscles cramps that can happen when you exercise or work in a hot, humid environment or extreme heat. It's one of several heat-related illnesses. The only sign of heat cramps are muscle spasms. These spasms are painful, brief, involuntary, they come and go (intermittent), and usually resolve on their own.

Reviewed on 5/20/2022
American Academy of Orthopaedic Surgeons. "Heat Injury and Heat Exhaustion." August 2021. <http://orthoinfo.aaos.org/topic.cfm?topic=a00319>.

Helman, R.S. "Heat Stroke." Medscape. Oct. 21, 2021. <http://emedicine.medscape.com/article/166320-overview>.

United States. CDC. "About Extreme Heat." June 19, 2017. <https://www.cdc.gov/disasters/extremeheat/heat_guide.html>.