A system for measuring the blood loss comprises a measuring device that determines the hemoglobin concentration of fluid within a container utilizing a light source and a light detector. The container receives blood and other fluids from a patient during a medical procedure. Light from the light source is passed through the blood and other fluids in the container and is detected by the light detector. Based upon a magnitude of light detected, the hemoglobin concentration of the fluid in the container can be determined. A volume-measuring device determines the volume of blood and fluid in the container. Knowing the hemoglobin concentration and volume of fluid in the container, the volume of patient blood loss in the container can be determined. The blood loss measuring device in combination with infusion systems maintains a real-blood volume status so that proper infusion of blood, crystalloid and/or colloid solutions occurs.