The most frequent fluid and electrolyte disorder in old age is dehydration. Result of normal age-related physiological modification comprise reduction in total-body water, alterations in thirst perception, and decreased renal function leading to reduced urine-concentrating ability. Disorders in fluid management in older adults may be caused by renal, gastrointestinal, endocrine disturbances, further by burns, pharmacotherapy and inappropriate intake of fluids and solutes. In addition, in the elderly the clinical signs of dehydration may be alterated, vague or even absent.