Hyperthermia, also known simply as overheating, is a condition in which an individual's body temperature is elevated beyond normal due to failed thermoregulation. The person's body produces or absorbs more heat than it dissipates. When extreme temperature elevation occurs, it becomes a medical emergency requiring immediate treatment to prevent disability or death.
Hyperthermia: Characterized on the left. Normal body temperature (thermoregulatory set-point) is shown in green, while the hyperthermic temperature is shown in red. As can be seen, hyperthermia can be considered an increase above the thermoregulatory set-point. Hypothermia: Characterized in the center: Normal body temperature is shown in green, while hypothermic temperature is shown in blue. As can be seen, hypothermia can be conceptualized as a decrease below the thermoregulatory set-point. Fever: Characterized on the right: Normal body temperature is shown in green. It reads "New Normal" because the thermoregulatory set-point has risen. This has caused what was the normal body temperature (in blue) to be considered hypothermic.
Hyperthermia affects those who are unable to regulate their body heat, mainly due to environmental conditions. The main risk factor for hyperthermia is the lack of ability to sweat. People who are dehydrated or who are older may not produce the sweat they need to regulate their body temperature.