Hematocrit

Medical Author:
Medical Editor:

What is the hematocrit?

The hematocrit is the proportion, by volume, of the blood that consists of red blood cells. The hematocrit (hct) is expressed as a percentage. For example, an hematocrit of 25% means that there are 25 milliliters of red blood cells in 100 milliliters of blood.

Picture of Red Blood Cells

How is the hematocrit measured?

The hematocrit is typically measured from a blood sample by an automated machine that makes several other measurements at the same time. Most of these machines in fact do not directly measure the hematocrit, but instead calculate it based on the determination of the amount of hemoglobin and the average volume of the red blood cells. The hematocrit can also be determined by a manual method using a centrifuge. When a tube of blood is centrifuged, the red cells will be packed into the bottom of the tube. The proportion of red cells to the total blood volume can be visually measured.



Patient Comments

Viewers share their comments

Hematocrit - Cause Question: What was the cause of your low hematocrit reading?

Get the latest health and medical information delivered direct to your inbox FREE!