Heat exhaustion can occur if the body loses an excessive amount of fluid. As your body becomes dehydrated, it overheats, and you may feel faint, dizzy, and lightheaded. If left untreated, heat exhaustion may progress to heat stroke, a life-threatening condition. At this stage, your temperature rises to a dangerous level, and you may no longer sweat due to extreme dehydration. A person suffering from heat stroke may be in a state of confusion and disorientation. If you suspect someone is experiencing heat stroke, press their Lifeline Personal Help button or call 911, get them out of the heat, and apply cold compresses on the body to lower their body temperature quickly.