Dehydration

In physiology, dehydration is a lack of total body water that disrupts metabolic processes. It occurs when free water loss exceeds intake, often resulting from excessive sweating, health conditions, or inadequate consumption of water. Mild dehydration can also be caused by immersion diuresis, which may increase risk of decompression sickness in divers. Most people can tolerate a 3–4% decrease in total body water without difficulty or adverse health effects. A 5–8% decrease can cause fatigue and dizziness. Loss of over 10% of total body water can cause physical and mental deterioration, accompanied by severe thirst. Death occurs with a 15 to 25% loss of body water. Mild dehydration usually resolves with oral rehydration, but severe cases may need intravenous fluids. Dehydration can cause hypernatremia (high levels of sodium ions in the blood). This is distinct from hypovolemia (loss of blood volume, particularly blood plasma). Chronic dehydration can cause kidney stones as well as the development of chronic kidney disease.