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The hematocrit is the volume of red blood cells in comparison to the total blood volume. It is expressed as a percentage. The hematocrit is measured with a blood count (CBC), a laboratory test performed on a blood sample. The hematocrit is between 40 and 55% in men. In women, it varies between 35 and 50%. Its variations can highlight pathologies.


A decrease in the hematocrit may indicate anemia in most cases (decreased red blood cells or hemoglobin). It can have different causes: iron deficiency, inflammation, intestinal malabsorption (pernicious anemia), excessive blood loss.
Anemia results in:

An increase in hematocrit indicates a polycythemia (increased red blood cell count). Polycythemia may be primitive. This is the case in polycythemia vera. It is a condition that will affect the bone marrow, the source for the synthesis of red blood cells. The latter will often be way too high in number. This may be due to heart disease, tumors, or an increased synthesis of hormones that stimulate the production of red blood cells. In the case of polycythemia, blood is thicker and the main risk is the occurrence of thrombosis, blood clots that can block overall blood flow.
Polycythemia causes:


The hematocrit alone cannot be used to make a diagnosis. The test will be supplemented by others to highlight the pathology in question. Hematocrit is measured simultaneously with hemoglobin levels, red blood cell count, and mean corpuscular volume (MCV). An interpretation of the hematocrit may be done in addition to the interpretation of the rest of the blood globular levels.


Treatment will depend on the condition that caused the change in red blood cell count. In the case of polycythemia vera, treatment with certain medications is also recommended.