Dehydration is the excessive loss of water and electrolytes (minerals that help maintain fluid balance) from the body. Water and electrolytes are essential to support normal body functioning.

Dehydration can quickly progress from mild to moderate to severe within hours, especially in infants and young children. Dehydration may involve primarily water loss, primarily electrolyte (e.g., sodium) loss, or the loss of equal amounts of both. Determining the specific fluid/electrolyte imbalance that is present can help ensure that appropriate replacement fluids are used.

Symptoms of mild dehydration may include thirst, headaches and dark yellow urine. Moderate cases of dehydration may include dry mouth, little or no urine, sluggishness, a rapid heartbeat and lack of skin elasticity. Severe dehydration, a life-threatening condition, is characterized by extreme thirst, no urine or tears, rapid breathing, an altered mental state and cold, clammy skin.

Mild dehydration is common, and usually caused by not drinking enough fluids throughout the day. Fluids are continuously lost through normal body functions such as sweating, breathing and urinating. Illness (e.g., diarrhea, vomiting), physical activity and climate conditions (e.g., heat and humidity) can cause fluid loss and increase the risk of dehydration. Certain populations are at higher risk of developing moderate to severe dehydration. These include infants and small children, people with chronic illnesses and the elderly.

Physicians can usually identify dehydration after compiling a medical history (including a discussion of the patient’s symptoms) and performing a physical examination. Urine and blood tests may be used to confirm the diagnosis.

Treatment in mild cases of dehydration often involves drinking adequate amounts of water and eating foods with high water content. Other types of fluids may also be used. In some moderate to severe cases of dehydration, the use of intravenous (I.V.) fluids and hospitalization may be necessary.