What it is: A hematocrit test measures the percentage of blood volume made up of red blood cells, typically as part of a complete blood count.
Why it's ordered: Ordered alongside a CBC to help diagnose or monitor anemia, dehydration, or polycythemia (an overproduction of red blood cells).
What it detects: A low hematocrit suggests anemia or blood loss; a high hematocrit can reflect dehydration, lung or heart disease affecting oxygen levels, or a bone marrow disorder that overproduces red blood cells.
Collection & prep: A standard blood draw from a vein in the arm, as part of a CBC. No special preparation is typically required.
Results:
Low – suggests anemia or blood loss
High – suggests dehydration or excess red blood cell production
Normal – roughly 38.3–48.6% for men and 35.5–44.9% for women, varying by lab
Possible complications of an abnormal result: Hematocrit is usually interpreted together with hemoglobin and red blood cell indices rather than alone, since isolated abnormal values can reflect hydration status as much as an underlying blood disorder.
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