Hyperthermia
A condition of failed thermoregulation causing dangerously elevated body temperature.
Hyperthermia, or overheating, happens when the body’s temperature rises above normal because its internal cooling system fails. The body either makes or takes in more heat than it can release. The International Emergency Medicine Education Project notes that severe hyperthermia—a body temperature above 40 °C (104 °F)—is a medical emergency that needs immediate care to avoid disability or death. Each year, nearly half a million people die from this condition.
Common triggers include heat stroke and reactions to certain drugs. Heat stroke is a sudden temperature spike caused by too much heat or a mix of heat and humidity that overpowers the body’s heat-regulating systems. Drug-induced hyperthermia is a rarer side effect of many medications, especially those affecting the central nervous system. Malignant hyperthermia is an uncommon complication of some general anesthetics. Traumatic brain injury can also cause hyperthermia.
Unlike a fever, hyperthermia does not change the body’s temperature set point. Its opposite is hypothermia, where body temperature drops below the level needed for normal metabolism. The word comes from Greek: *hyper* meaning “above” and *thermos* meaning “heat.” The highest recorded body temperature in a survivor of hyperthermia was 46.5 °C (115.7 °F), measured on July 10, 1980, in a man hospitalized for severe heat stroke.
**Classification**
In humans, hyperthermia is defined as a temperature above 37.5–38.3 °C (99.5–100.9 °F), depending on the reference, without a shift in the body’s temperature set point. Normal body temperature can reach 37.7 °C (99.9 °F) in the late afternoon. Hyperthermia means a rise above what would normally be expected. These elevations range from mild to extreme; temperatures over 40 °C (104 °F) can be life-threatening.
**Signs and Symptoms**
An early stage, called heat exhaustion (or heat prostration or heat stress), may involve heavy sweating, rapid breathing, and a fast, weak pulse. If it progresses to heat stroke, the skin often becomes hot and dry as blood vessels widen to try to release heat. An inability to cool down through sweating can cause dry skin. Hyperthermia from neurological disease may include little or no sweating, cardiovascular problems, and confusion or delirium.
Other symptoms vary.
Quick Facts
- Synonym
- Overheating
- Specialty
- Critical care medicine
- Symptoms
- Lack of perspiration, confusion, delirium, decreased blood pressure, increased heart rate and respiration rate, symptoms of dehydration
- Complications
- Organ failure, unconsciousness
- Causes
- Heat stroke, neuroleptic malignant syndrome, malignant hyperthermia, serotonin syndrome
- Risks
- Exposure to hot and/or humid environments, physical exertion, wearing personal protective equipment that covers the body, heatwaves
- Diagnosis
- Based on symptoms or body temperature above 37.7 C
- Differential
- Fever
- Prevention
- Maintaining a moderate temperature, regular hydration, taking regular breaks
Facts from the source article.
Lore & Background
Hyperthermia is defined as a temperature greater than 37.5–38.3 °C (99.5–100.9 °F) that occurs without a change in the body's temperature set point, distinguishing it from fever. The term comes from Greek ὑπέρ (hyper, meaning 'above') and θέρμος (thermos, meaning 'heat'). The opposite condition is hypothermia, where temperature drops below that required for normal metabolism. The highest recorded body temperature in a patient who survived hyperthermia is 46.5 °C (115.7 °F), measured on 10 July 1980 from a man admitted to hospital for serious heat stroke.
Early stages of hyperthermia can include heat exhaustion, with symptoms such as heavy sweating, rapid breathing, and a fast, weak pulse. If it progresses to heat stroke, hot, dry skin is typical as blood vessels dilate to increase heat loss. Severe cases may involve confusion, aggressive behavior, increased heart and respiration rates, and decreased blood pressure. Young children may have seizures, and eventually organ failure, unconsciousness, and death can result. The most common causes include heat stroke and adverse reactions to drugs, with malignant hyperthermia being a rare complication of some types of general anesthesia. Traumatic brain injury can also cause hyperthermia.
Reader's Guide
Hyperthermia is notable for its significant global mortality, with almost half a million deaths recorded annually. The condition is a medical emergency when body temperature exceeds 40 °C (104 °F), requiring immediate treatment to prevent disability or death. Heat stroke, the most common cause, occurs when thermoregulation is overwhelmed by excessive heat, exertion, or humidity. Drug-induced hyperthermia, though rarer, is associated with many psychotropic medications, recreational drugs, and anesthetic agents. Situational heat stroke primarily affects the young and elderly, often precipitated by medications that reduce vasodilation and sweating. During the July 1995 heatwave in Chicago, at least 700 heat-related deaths occurred, with risk factors including being confined to bed and living alone. The use of personal protective equipment (PPE) in industrial, military, or healthcare settings can inadvertently increase heat stress by creating a microclimate that impairs natural thermoregulation. This was notably observed during the 2014 Ebola virus epidemic in Western Africa, where healthcare workers could only work for 40 minutes at a time due to hyperthermia risk.
Did You Know?
- Almost half a million deaths are recorded every year from hyperthermia.
- Hyperthermia differs from fever in that the body's temperature set point remains unchanged.
- During the July 1995 heatwave in Chicago, there were at least 700 heat-related deaths.
Frequently Asked Questions
What is Hyperthermia?
Hyperthermia is a medical condition in which the body's internal cooling mechanisms break down, causing core temperature to climb beyond the normal upper limit of 37.7 °C (99.9 °F). It occurs whenever heat production or heat absorption outpaces the body's ability to shed that excess warmth.
What are the most common triggers of Hyperthermia?
The two leading culprits are heat stroke—where environmental heat overwhelms the body's defenses—and adverse drug reactions that disrupt normal temperature regulation. In both scenarios the result is a rapid, dangerous spike in core temperature.
At what point does Hyperthermia become a life-threatening emergency?
Once core temperature crosses 40 °C (104 °F), the condition is classified as severe and demands immediate medical intervention. Without prompt treatment, it can progress to permanent organ damage or death.
How many lives does Hyperthermia claim each year?
Roughly half a million people worldwide die from hyperthermia annually, making it one of the deadliest external-cause effects. The International Emergency Medicine Education Project flags it as a critical public-health concern.
What is the highest body temperature anyone has survived?
The record stands at 46.5 °C (115.7 °F), a temperature reached by a patient on 10 July 1980. That case remains the extreme upper limit of human survival under hyperthermic conditions.
More in Effects of External Causes 1-24
Spotted an error? Know more?
Reader corrections go straight into our review queue. Suggest an edit · How this site is sourced