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Definition
By Mayo Clinic staffHematocrit (he-MAT-uh-krit) is the proportion of your blood composed of red blood cells. Hematocrit (Hct) is also called packed-cell volume (PCV).
Red blood cells, or erythrocytes (uh-RITH-ro-sites), are cells that transport oxygen throughout your body. A hematocrit test indicates whether you have too few or too many red blood cells — conditions that can occur as the result of certain diseases.
Your hematocrit value is determined from a sample of your blood. A technician puts the sample in a device called a centrifuge that spins the blood very quickly in a test tube. This motion separates your blood into three parts: the fluid component of blood (plasma), red blood cells and other blood cells. When the blood is separated, the technician can determine what proportion of the cells are red blood cells.
- Fischbach FT, et al. Manual of Laboratory and Diagnostic Tests. Online ed. Philadelphia, Pa.: Lippincott Williams & Wilkins; 2008.
- McPherson RA, et al, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 21st ed. Philadelphia, Pa.: Saunders Elsevier; 2007.
- Laboratory reference values. Hematocrit. Rochester, Minn.: Mayo Foundation for Medical Education and Research; Nov. 2008.
