In some cases victims, especially the elderly, should be hospitalized. Heat exhaustion is more likely after a few days of a heat wave than when one is just beginning. The best defense is to take it easy and drink plenty of water. Don't take salt tablets without consulting a physician. In some cases extreme heat can upset the body's thermostat, causing body temperature to rise to 105 degrees or higher.
Symptoms are lethargy, confusion and unconsciousness.
Even a suspicion that someone might be suffering from heatstroke requires immediate medical aid. Heatstroke can kill.