Normohydration

Normohydration is the physiological state in which the body's total body water remains within the normal range for a person’s age, sex, body composition, and environment, with stable plasma osmolality and extracellular fluid volume. It is often used interchangeably with euhydration, though normohydration emphasizes a balanced baseline under typical conditions. This state reflects a dynamic equilibrium between fluid intake and fluid losses.

Hydration status is assessed using multiple indicators because no single measure is definitive. Practical indicators include changes in body weight, urine color and volume, and urine specific gravity or osmolality. Blood tests can assess plasma osmolality and sodium concentrations. More advanced techniques, such as bioelectrical impedance analysis, can estimate body water compartments. In clinical and athletic settings, a combination of measures provides the most reliable picture of normohydration.

Maintaining normohydration involves regular fluid intake to offset losses from respiration, perspiration, urine, and feces. The balance is influenced by activity level, ambient temperature and humidity, health status, and dietary factors. For athletes, staying within the normohydration range supports thermoregulation, cognitive function, mood, and physical performance, while both dehydration and excessive fluid intake can impair function and comfort.

In health care and public health, normohydration serves as a reference target for hydration strategies and monitoring. Illness, diuretic use, kidney disorders, or extreme environmental conditions can disrupt this balance, necessitating appropriate adjustments in fluid intake and monitoring.