Medication error is a frequent adverse event in health care. In this study, we checked each medication dose in 744 medical orders and identified a prevalence rate of 0.53 medication errors per medical order. The highest prevalence was in the critical care unit (0.98), and the most frequent type was dose omission (53%). The results were published bimonthly for health care professionals, with an improvement recommendation list to minimize medication errors and increase patient safety.