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Symptoms and Signs of Heat Exhaustion vs. Heat Stroke: How to Tell the Difference

Doctor's Notes on Heat Exhaustion vs. Heat Stroke: How to Tell the Difference

Heat exhaustion and heat stroke are related conditions that develop when a person’s body becomes overheated because the body cannot cool itself rapidly enough to prevent an increased body core temperature. The signs and symptoms for heat exhaustion are usually the same for early heat stroke; however, heat stroke has additional life-threatening signs and symptoms. Heat exhaustion symptoms and signs are as follows: pale, cool and clammy skin, profuse sweating, dizziness or lightheadedness and a core body temperature (best measured by a rectal thermometer) of more than 100 F (37.7 C) but not above 104 F (40 C). These can be considered early warning signs of heat stroke if the patient tries to continue activity and is not treated. Heat stroke signs and symptoms are worsening of the above resulting in flushed dry skin, ceased sweating, core body temperature of 105 F (40.5 C) or more, fainting and confusion. The heat stroke patient can also develop blood pressure changes (high or low levels), hyperventilation, coma and death.

The cause of both heat exhaustion and heat stroke is the body’s inability to cool its core temperature to keep it in a normal range. Work or play in a humid and hot environment where sweating cannot cool the body leads to dehydration and potentially rapid onset of symptoms that need urgent and/or emergent care.

Medical Author:
Medically Reviewed on 3/11/2019


Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.