This patient presented with altered mental status and hypernatremia. Initial workup found a serum sodium of 151 mEq/L, urine sodium of 20 mEq/L, and a urine osmolality less than 1%. A water deprivation test confirmed the diagnosis of central diabetes insipidus, as the patient continued to produce dilute urine despite becoming hypernatremic and hyperosmolar. Central diabetes insipidus was likely caused by damage to the hypothalamus preventing adequate release of antidiuretic hormone.