Uroflowmetry is considered a simple and noninvasive test in the evaluation of urinary symptoms. It requires patients to consume fluid orally for a full bladder prior to undertaking the test. Guidelines regarding the amount and rate of oral fluid intake have not been accurately defined. We report on a patient who suffered a serious complication of water intoxication with hyponatremia and seizure due to excessive water consumption and absorption during uroflowmetry. We discuss the underlying factors concerning this complication and recommend a more conservative approach to attain a full bladder in a certain subgroup of patients at risk of developing such a complication.