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Latest Edit: Hector 2014-03-24 (EDT)

See Also Lab Tests

Hematocrit or Hct, is an indirect measurement of red blood cell (RBC) number and volume. It is used routinely as part of the complete blood cell count and is an integral part of the evaluation of anaemia. The Hct is a measure of the percentage of the total blood volume that is made up by the RBCs.[1],[2]

Patient Preparation

  • Fasting is not required for this test.

Interfering Factors:

  • Women tend to have lower values than men.
  • Hct values tend to decrease with age.
  • Abnormalities in RBC size may alter Hct values. Larger RBCs are associated with higher Hct levels.
  • Extremely elevated white blood cell count decreases Hct.
  • Dehydration can affect Hct levels.
  • Pregnancy can cause slightly decreased levels.
  • Living in high altitudes may increase Hct levels.
  • Recent hemorrhage can disrupt levels.
  • Drugs that may cause decreased levels include chloramphenicol and penicillin.

Clinical Implications

Hct is primarily used as a test for anaemia, but it can also indicate:

High levels indicate:

Low levels indicate:

Associated Tests

A Hct test is typically part of a complete blood count which includes hemoglobin and red blood cell count which are closely associated with Hct.


  1. Pagana Kathleen D, Pagana Timothy J (2006) Mosby's Manual of Diagnostic and Laboratory Tests, Mosby.
  2. Weatherby Dicken, Ferguson Scott (2002) Blood Chemistry and CBC Analysis: Clinical Laboratory Testing from a Functional Perspective, Bear Mountain.