Hypernatremia in elderly patients is most often due to the patients' mental incapacity or physical inability to obtain water despite intact thirst sensation. Hypodipsia leading to hypernatremia is not often considered in alert, elderly subjects since hypodipsia is not a recognized consequence of nonaphasia-producing cerebrovascular accidents. Described herein are six elderly patients who had such cerebrovascular accidents and who had recurrent hospitalizations for dehydration and hypernatremia. Hypernatremia in this group was due to hypodipsia and could only be prevented by prescribing daily fluid intake as a medication order. Hypodipsia should be considered as a cause of hypernatremia in elderly subjects even when they seem fully capable of requesting and obtaining water.