The present invention is directed to a dialysis system with a disconnection monitor for determining if a blood line connection to a patient has been disconnected. It includes a blood circuit in fluid communication with a patient and a dialysis circuit, a pressure transducer for generating a signal indicative of a pulse signal in the blood circuit, a cardiac reference signal generator for generating a signal indicative of the patient's pulse and a disconnection monitor. The disconnection monitor includes a pressure transducer data receiver for receiving the signal indicative of the pulse signal in the blood circuit, a cardiac reference signal receiver for receiving the signal indicative of the patient's pulse, and a processor for cross-correlating the signal indicative of the pulse signal in the blood circuit and the signal indicative of the patient's pulse to generate data indicative of a disconnection of the blood line connection to the patient.
