Overhydration, also called water excess or water intoxication, is a condition in which the body contains too much water. It occurs when the body takes in more water than it excretes, and its normal sodium level is diluted. This can result in digestive problems, behavioral changes, brain damage, seizures, or coma. An adult whose heart, kidneys, and pituitary gland are functioning properly would have to drink more than two gallons of water a day to develop water intoxication. The condition is most common in patients whose kidney function is impaired and may occur when health care professionals administer greater amounts of water-producing fluids and medications than the patient's body can handle.

Infants are especially likely to develop overhydration. The Centers for Disease Control and Prevention has cautioned that babies are particularly susceptible to the problem during the first month of life, when the kidneys' filtering mechanism is too...