Dehydration

Dehydration is a condition in which the body loses more water than it takes in. It reduces the water available for normal physiological functions.

Osmoregulation: The regulation of water and dissolved substances in an organism’s fluids. The body adjusts thirst and kidney water retention as dehydration changes fluid concentration.
Gastroenteritis: Inflammation of the stomach and intestines, commonly causing diarrhea and vomiting. These symptoms can rapidly remove water and salts from the body.
Total body water: The water contained within the body, distributed across cells and extracellular spaces. Dehydration is a deficit in this body-wide water supply.
Overhydration: A state in which the body contains excess water relative to its needs. It is the opposite direction of water imbalance.
Antidiuretic hormone: A hormone that helps the kidneys conserve water by reducing urine production. Rising release helps limit water loss through the kidneys.
Heat illness: A range of disorders caused by excessive heat exposure, from cramps to heatstroke. Sweating in hot conditions increases water loss and dehydration risk.
Extracellular fluid: Body fluid located outside cells, including blood plasma and fluid between cells. Water loss changes this compartment and can affect circulation.
Edema: Swelling caused by excess fluid in the spaces between body cells. Visible tissue fluid can coexist with low effective circulating volume, unlike simple dehydration.
Thirst: The conscious drive to drink, triggered largely by changes in body water and dissolved substances. Increasing thirst encourages fluid intake as water deficit develops.
Oral rehydration therapy: Treatment using a drink containing water, glucose, and electrolytes to replace losses. It replaces fluid and salts, especially during diarrheal illness.

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