The McGill Physiology Virtual Lab

Blood Laboratory

Blood cell indices > Hematocrit
  When heparinized blood (heparin is an anticoagulant) is centrifuged, the red blood cells become packed at the bottom of the tube, while the plasma is left at the top as a clear liquid. The ratio of the volume of packed red cells to the total blood volume is called the hematocrit.


Heparinized blood is transferred from the microcentrifuge tube (often called eppendorf tube) to a microhematocrit capillary. The tube is filled to at about 3/4 capacity by capillary action.

Then the blood-filled end is sealed with clay, and placed in a slot in the hematocrit centrifuge.

In order to obtain a value of hematocrit from the centrifuged blood sample in the capillary tube, one must refer to a scale plate, which is located directly under the samples in the centrifuge. The bottom of the packed red cell column is first lined up with the "0" line on the scale plate, and then the scale is moved under the sample until the top of the plasma column lines up with the"100%" line. In the example animation given below, watch as first one, and then a second sample tube moves over the grid. A black square on the right will give you a digital reading at a given point, but make sure that you note the right one!


  • You should have obtained a value of 44% for the first tube, and 37% for the second tube.
  • Note that the normal range of values for hematocrit are as follows:
    Female: 36-48%
    Male: 40-52%

To continue to the next section Hemoglobin content determination, click here