Hydration

Hydration refers to the state of having an adequate amount of body water necessary for physiological processes. Water makes up a large portion of body weight and participates in digestion, circulation, temperature regulation, joint lubrication, and waste removal. Hydration status reflects the balance between water intake and water loss.

The body regulates hydration through thirst, hormonal signaling, and kidney function. When fluid levels drop, the kidneys conserve water, reducing urine output and increasing urine concentration. Hormones adjust thirst and urine production to maintain plasma osmolality. Hydration is influenced by climate, physical activity, health status, age, and medications.

Fluid sources include drinking water and beverages, as well as moisture from foods. Most people obtain a large portion from beverages and a substantial portion from foods. Daily needs vary; guidelines commonly cite about 3.7 liters for men and 2.7 liters for women as total intake from all sources, with higher needs during exercise or heat. Electrolytes such as sodium and potassium support fluid balance, particularly with sweating or illness.

Signs of adequate hydration include regular urination and pale, straw-colored urine; signs of dehydration include darker urine, dry mouth, thirst, dizziness, or confusion in severe cases. Severe dehydration or rapid weight loss requires medical evaluation.

Special considerations include older adults, who may have reduced thirst perception; athletes during intense exercise may need fluid and electrolyte replacement; illness with fever, vomiting, or diarrhea increases needs. Moderate caffeine intake contributes to daily fluid intake, but individual responses vary. In chronic conditions, healthcare providers can tailor fluid recommendations.