The maintenance of optimal water balance is a priority for homeostasis; unfortunately, the aging process adversely affects the mechanisms of water balance, making it more difficult for the body to adequately defend itself against water loss. Four major age-related changes predispose the elderly to dehydration and hypernatremia: a decrease in total body water, an altered sense of thirst, a decrease in the renal urine concentrating ability, and a decrease in the effectiveness of ADH. In the case of fluid balance, careful assessment cannot be overemphasized due to the fact that there are few symptoms unique to dehydration that readily allow a nurse to know that fluid imbalances are involved.