Definition of dehydration


A condition that occurs when the body loses too much water and other fluids that it needs to work normally. Dehydration is usually caused by severe diarrhea and vomiting, but it may also be caused by not drinking enough water or other fluids, sweating too much, fever, urinating too much, or taking certain medicines. Signs and symptoms include thirst, dry mouth, headache, fatigue, dark-colored urine, urinating less than normal, sunken eyes or cheeks, dry and cool skin, dizziness, fainting, muscle cramps, rapid heartbeat, and rapid breathing. Dehydration can be severe, especially in young children and older adults.

Source: NCI Dictionary of Cancer Terms