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Hematocrit

Also known as: Hct, Crit, Packed cell volume (PCV)
Related tests: Complete blood count
The Test
 
How is it used?
When is it ordered?
What does the test result mean?
Is there anything else I should know?

How is it used?
This test is used to evaluate:

  • anemia (decrease of red blood cells), 
  • polycythemia (increase in red blood cells), 
  • dehydration
  • blood transfusion decisions, and
  • the effectiveness of those transfusions.



When is it ordered?
The hematocrit is normally ordered as a part of the complete blood count (CBC). It is also repeated at regular intervals for many conditions, including:

  • the diagnosis of anemia
  • the treatment of anemia, 
  • recovery from dehydration, and
  • monitoring of ongoing bleeding to check its severity.



What does the test result mean?
Decreased hematocrit indicates anemia, such as that caused by iron deficiency. Further testing may be necessary to determine the exact cause of the anemia.

Other conditions that can result in a low hematocrit include vitamin or mineral deficiencies, recent bleeding, cirrhosis of the liver, and malignancies.

The most common cause of increased hematocrit is dehydration, and with adequate fluid intake, the hematocrit returns to normal. However, it may reflect a condition called polycythemia vera—that is, when a person has more than the normal number of red blood cells. This can be due to a problem with the bone marrow or, more commonly, as compensation for inadequate lung function (the bone marrow manufacturers more red blood cells in order to carry enough oxygen throughout your body). Anytime a hematocrit is persistently high, the cause should be determined in consultation with a doctor.

With regard to transfusions, this is normally not considered for otherwise healthy persons as long as the hemoglobin level is above 8 grams per deciliter or the hematocrit is above 24%.

PLEASE NOTE: Numerically reported test results are interpreted according to the test's reference range, which may vary by the patient's age, sex, as well as the instrumentation or kit used to perform the test. A specific result within the reference (normal) range – for any test – does not ensure health just as a result outside the reference range may not indicate disease. To learn more about reference ranges, please see the article, Reference Ranges and What They Mean. To learn the reference range for your test, consult your doctor or laboratorian. Lab Tests Online recommends you consult your physician to discuss your test results as a part of a complete medical examination.



Is there anything else I should know?
Pregnancy usually causes slightly decreased hematocrit values due to extra fluid in the blood.

Living at high altitudes causes increased hematocrit values—this is your body’s response to the decreased oxygen available at these heights.





This page was last modified on November 12, 2003.
 
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