Ventricular assistance devices have been very useful to the patients with chronic heart failures. But, regular consumption of anticoagulants to suppress the thrombosis results into many bleeding related complications. Such complications are also observed in the patients getting hemodialysis and patients undergoing heart surgery using heart-lung machine. Currently, the anticoagulation management is based on offline tests. But, the real-time non-invasive blood monitoring system is highly desirable to optimize the anticoagulation therapy. As a basic study in that direction, we employed electrical impedance spectroscopy method to study the electrical chacteristics of bovine blood under thrombogenic condition. The resistance and reactance were measured in the frequency range of 1 kHZ to 5 MHz. The measured values were then analyzed using equivalent circuit fitting. It was observed that the capacitance of the blood can be used to quantitatively measure the degree of aggregation of red blood cells in the blood undergoing thrombosis.