A drip infusion path monitoring system employing a low power, 8-bit, one chip microcomputer has been developed for hospital and home use. The system monitors the security of a drip infusion path. Drip infusion fluids have electrical conductivity which enables them to conduct an electrical curent. This system continuously monitors an electric current passed from the drip infusion polyvinyl chloride tube to the body. The current is applied to the infusion tube by capacitor coupling with 30kHz and is detected by an electrode attached to the skin. If the patient pulls out the injection needle or catheter tube(consciously or unconsciously), then the monitoring system detects the interruption of current flow and generates a warning signal that calls the nurse or nurse assistant. The system can also detect if the patient's hand grasped the tube before the injection needle or catheter was pulled out.