Abstract: A blood loss monitoring apparatus is disclosed. The system includes a tank having a solution which removes blood from blood containing materials which are deposited in the tank and also hemolyzes the blood. Blood and blood containing materials are deposited into the tank during surgery, and the volume of liquid in the tank as well as the hemoglobin concentration in the tank are then determined. From this information, the total amount of hemoglobin lost is determined, and by measuring the patient's hemoglobin level immediately prior to the surgery, the total amount of blood lost is then calculated. The amount of blood lost can be continuously monitored and updated throughout the course of the surgical procedure or operation.