Apparatus and method for using ultrasound to determine hematocrit

This invention is an ultrasound apparatus for determining hematocrit. A sample of blood in a microhematocrit capillary tube is acoustically coupled to an ultrasound transducer which creates a standing wave in the blood sample. Red blood cells in the blood sample are packed in bands that correspond to the nodes of the standing wave. The thickness of the bands as a function of the thickness of the remaining plasma is an indication of the hematocrit of the blood sample.