Heatstroke is a potentially life-threatening condition in which the body's ability to cool itself stops functioning correctly and body temperature rises to dangerous levels.


Heatstroke is the most dangerous of the heatrelated illnesses. It is more serious than either heat cramps or heat exhaustion. Untreated heatstroke can cause death. Heatstroke occurs most frequently during heat waves and during very hot, humid weather. It is especially common among athletes and other individuals engaging in outdoor activities in very hot weather. However, it can occur even without significant exertion, just by exposure to very hot conditions. Because heatstroke and other heat-related illnesses are a serious public health concern during periods of very hot weather, many cities open schools and other airconditioned buildings to young children, the elderly, and others at risk for heatstroke so that they can have cool, safe places to spend the hottest parts of the day.

Risk factors

Anyone can get heatstroke. However, the elderly and young children are more likely to be affected than young or middle-aged adults. Obese individuals and those with cardiovascular problems are also at increased risk. Alcohol and diseases that impair the ability to sweat are associated with a higher risk of heatstroke.

Individuals taking certain medications are more likely to be affected because the medications can interfere with the body's normal cooling mechanisms. Individuals taking some blood pressure and heart medications, allergy medications, diet pills, diuretics (water pills), cold medicines, medicines to prevent seizures, laxatives, and thyroid pills are at increased risk for heatstroke.


The United States Centers for Disease Control and Prevention (CDC) report that more than 330 individuals die of heat-related causes each year. More deaths occur in years that have significant heat waves, and more individuals die of heat-related illness during the summer months. More than 40% of the individuals who die of heat-related causes each year are over the age of 65.

Heatstroke (left) and heat exhaustion (right) manifest in very different ways.

Causes and symptoms

Heatstroke is caused by the body being unable to cool itself effectively. Normally, the body cools itself by sweating. The sweat dampens the surface of the skin and then evaporates, causing a cooling effect. When the body's ability to sweat is compromised, or the conditions are so hot and humid that sweating is not producing enough of a cooling effect, the internal temperature of the body begins to rise and heatstroke can occur.

Heatstroke is caused by a significant rise in body temperature. An individual experiencing heatstroke typically has a body temperature above 104°F (40°C). The individual often has skin that is dry and warm, but in many cases is no longer sweating. If the individual was recently doing strenuous exercise, the skin may still feel moist. The individual's heart rate increases, and he or she may begin to hyperventilate (rapid, shallow breathing). Headache, nausea, and fatigue may occur. The individual may appear to be confused and may have difficulty understanding or responding to things that are said. Heatstroke can lead to dizziness, hallucinations, and even to seizures and coma.


Ions in the body that participate in metabolic reactions. The major human electrolytes are sodium (Na+), potassium (K+), calcium (Ca2+), magnesium (Mg2+), chloride (Cl-), phosphate (HPO42-), bicarbonate (HCO3-), and sulfate (SO4 2-). Careful and regular monitoring of electrolytes and intravenous replacement of fluid and electrolytes are part of the acute care in many illnesses including heatstroke.
Rapid, shallow breathing.
Intravenous (IV)—
The process of giving a liquid through a vein.
A substance that stimulates movement of food through the bowels. Laxatives are used to treat constipation.
A sudden attack, spasm, or convulsion.


The goals of heatstroke treatment are to lower the body's temperature and to help the body's natural cooling mechanisms begin functioning again. When an individual seems to have the signs and symptoms of heatstroke, medical attention should be sought immediately. While waiting for help to arrive, the individual should be moved to an air-conditioned building or a place in the shade. The individual should be given cool, noncaffeinated, nonalcoholic liquid if they are able to drink. The individual can be sprayed with cool water or even submersed in a bathtub of cool water to help bring down the body temperature. Fanning the individual to help circulate air over the damp skin can mimic the act of sweating and help reduce body temperature.

Heatstroke is a medical emergency. An individual experiencing heatstroke should be taken to the hospital as quickly as possible. There, the emergency room staff will reduce the individual's body temperature in one or more ways. The individual may be placed in a bath of cool or ice water. The doctor may instead choose to place the individual under cooling blankets and put ice packs where the blood flows closest to the surface of the body, such as the armpits, behind the neck, and the groin area. Another option is spraying the patient with cool water and then using a fan to move warm air over the body to simulate sweating.

Additional fluids and medications may be given intravenously during the treatment. Shivering is the body's natural response to cold conditions, and the patient being treated may begin to shiver. Because shivering is designed to warm up the body, it is counterproductive when an individual is being treated for heatstroke. If the patient begins to shiver during treatment, the doctor may administer a muscle relaxant to stop the shivering and allow the cooling treatment to continue.

When individuals experience heatstroke they are not getting enough fluids. Often the electrolytes are depleted as well. Drinking fluids such as water that do not contain caffeine, alcohol, or large amounts of sugar can help restore fluid levels and improve the body's ability to sweat. Drinking isotonic sports drinks such as Gatorade can help to restore both fluids and electrolytes.


Untreated heatstroke can be fatal. Even when not fatal, it can lead to permanent damage to the organs, muscles, central nervous system, cardiovascular system, and brain. Heatstroke is, however, extremely treatable when the signs and symptoms are detected early. Individuals are more likely to die of heatstroke if they are not producing urine, are in a coma, or have heart failure when they arrive at the hospital. Treating heatstroke early can prevent these complications.


The key to preventing heatstroke is to avoid exertion during very hot days, to stay out of direct sunlight, and to drink plenty of fluids. Individuals should wear light, loose fitting clothing on hot days to help allow sweat to evaporate and cool the body efficiently. Individuals should drink two to four 8-oz. glasses of water every hour in extremely hot weather, even if they do not feel thirsty. On very hot days when people begin to feel thirsty it is a sign that there is already a problem. Individuals who are at increased risk of heatstroke should try to spend as much of the day as possible in air-conditioned buildings or in the shade. Senior centers, community centers, churches, and other organizations often open on hot days to allow individuals a place to stay out of the heat.

  • Do any of my medications put me at increased risk for heatstroke?
  • Do any of my diseases or conditions put me at increased risk for heatstroke?
  • What are some strategies to ensure I can still participate in my favorite activities while not putting myself at risk of heatstroke?
  • Do any of my outdoor fitness activities put me at an increased risk of heatstroke?

Any signs of heat-related illness should be taken extremely seriously. Beginning treatment when heat cramps or heat exhaustion occur and before they progress to heatstroke can prevent heatstroke and dangerous complications. Individuals should avoid drinks that contain alcohol, large amounts of sugar, and caffeine on very hot days. These substances can actually inhibit the body's ability to cool itself, so drinking them may increase the severity of the heatrelated illness instead of treating it.



Clay, Richmond, L. Special Events Medical Services. Sudbury: Jones and Bartlett, 2011.

Towell, Colin. The Survival Handbook: Essential Skills for Outdoor Adventure, 2nd ed. New York: DK Publishing, 2012.


Bray, Patricia, Rosemary Sokas, and Jaspa Ahluwalia. “Heat-Related Illnesses: Opportunities for Prevention.” Journal of Occupational and Environmental Medicine 52, no. 8 (August 2010): 844–5.

Day, Michael W. “Keeping Your Cool When Heatstroke Strikes.” Nursing 40 (2010): 9–11.

Yard, Ellen E., et al. “Heat Illness Among High School Athletes.” Journal of Safety Research 41, no. 6 (December 2010): 471–4.


“Heat Exhaustion and Heatstroke.” American Academy of Family Physicians. FamilyDoctor.org . December 2010. https://familydoctor.org/heat-exhaustion-and-heatstroke (accessed January 24, 2017).

“Heat Stroke: First Aid.” MayoClinic. March 31, 2015. http://www.mayoclinic.org/first-aid/first-aid-heatstroke/basics/art-20056655 (accessed January 24, 2017).


National Athletic Trainers' Association, 1620 Valwood Pkwy., Ste. 115, Carrollton, TX, (214) 637-6282, # http://www.nata.org/ #.

Helen Colby, MA
Revised by Tish Davidson, AM

  This information is not a tool for self-diagnosis or a substitute for professional care.