Objective To explore the characteristics and factors associated with interruptions during medication administration in endocrinology department, and to provide information for reducing interruptions and ensuring medication safety. Methods This study used direct observations of nurses while administrating medications to patients. Ten clinical nurses on day shift were observed at 9:00-12:00, then frequency, source, main role, time distribution, type and outcome of interruptions were analyzed. Results An average of 8.83 interruptions per hour occurred during medication administration, with the peak being 13.20 at 11:00-12:00. Family/patient interruptions were the most (62.3%), followed by fellow nurse (20.0%) and environment (12.8%). More than seventy percent (73.2%) of the interruptions were inducde by expected encounter, whereas just over ten percent (12.8%) of the interruptions were material initiated breaks. More than half were intrusions (52.1%) and 41.5% were distractions. Most interruptions (98.1%) had negative outcomes. Conclusion Interruptions during medication administration are prevalent in endocrinology department. It is of great significance to manage and control the main time period, source and main role of interrupted events, to ensure medication safety.