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Hematocrit Test

What is a Hematocrit Test?

A hematocrit test is a type of blood test. Your blood is made up of red blood cells, white blood cells, and platelets. These cells and platelets are suspended in a liquid called plasma. A hematocrit test measures how much of your blood is made up of red blood cells. Red blood cells contain a protein called hemoglobin that carries oxygen from your lungs to the rest of your body. Hematocrit levels that are too high or too low can indicate a blood disorder, dehydration, or other medical conditions.

Other names: HCT, packed cell volume, PCV, Crit; Packed Cell Volume, PCV; H and H (Hemoglobin and Hematocrit)

What is it used for?

A hematocrit test is often part of a complete blood count (CBC), a routine test that measures different components of your blood. The test is also used to help diagnose blood disorders such as anemia, a condition in which your blood doesn't have enough red cells, or polycythemia vera, a rare disorder in which your blood has too many red cells.

Why do I need a hematocrit test?

Your health care provider may have ordered a hematocrit test as part of your regular checkup or if you have symptoms of a red blood cell disorder, such as anemia or polycythemia vera. These include:

Symptoms of anemia:

Symptoms of polycythemia vera:

  • Blurred or double vision
  • Shortness of breath
  • Headache
  • Itching
  • Flushed skin
  • Tiredness
  • Excessive sweating

What happens during a hematocrit test?

A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.

Will I need to do anything to prepare for the test?

You don't need any special preparations for a hematocrit test. If your health care provider has ordered more tests on your blood sample, you may need to fast (not eat or drink) for several hours before the test. Your health care provider will let you know if there are any special instructions to follow.

Are there any risks to the test?

There is very little risk to having a hematocrit test or other type of blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.

What do the results mean?

If test results show your hematocrit levels are too low, it may indicate:

If test results show your hematocrit levels are too high, it may indicate:

  • Dehydration, the most common cause of high hematocrit levels. Drinking more fluids will usually bring your levels back to normal.
  • Lung disease
  • Congenital heart disease
  • Polycythemia vera

If your results are not in the normal range, it doesn't necessarily mean that you have a medical condition requiring treatment. To learn more about your results, talk to your health care provider.

Is there anything else I need to know about a hematocrit test?

Many factors can affect your hematocrit levels, including a recent blood transfusion, pregnancy, or living at a high altitude.

References

  1. American Society of Hematology [Internet]. Washington D.C.: American Society of Hematology; c2017. Blood Basics; [cited 2017 Feb 20]; [about 2 screens]. Available from: http://www.hematology.org/Patients/Basics/
  2. Hinkle J, Cheever K. Brunner & Suddarth's Handbook of Laboratory and Diagnostic Tests. 2nd Ed, Kindle. Philadelphia: Wolters Kluwer Health, Lippincott Williams & Wilkins; c2014. Hematocrit; p. 320–21.
  3. Mayo Clinic [Internet]. Mayo Foundation for Medical Education and Research; c1998–2017. Hematocrit Test: Overview; 2016 May 26 [cited 2017 Feb 20]; [about 2 screens]. Available from: http://www.mayoclinic.org/tests-procedures/hematocrit/home/ovc-20205459
  4. Lab Tests Online [Internet]. Washington D.C.: American Association for Clinical Chemistry; c2001–2017. Hematocrit: The Test; [updated 2015 Oct 29; cited 2017 Feb 20]; [about 4 screens]. Available from: https://labtestsonline.org/understanding/analytes/hematocrit/tab/test/
  5. Lab Tests Online [Internet]. Washington D.C.: American Association for Clinical Chemistry; c2001–2017. Hematocrit: The Test Sample; [updated 2016 Oct 29; cited 2017 Feb 20]; [about 3 screens]. Available from: https://labtestsonline.org/understanding/analytes/hematocrit/tab/sample/
  6. Lab Tests Online [Internet]. Washington D.C.: American Association for Clinical Chemistry; c2001–2017. Hematocrit: At a Glance; [updated 2015 Oct 29; cited 2017 Feb 20]; [about 2 screens]. Available from: https://labtestsonline.org/understanding/analytes/hematocrit/tab/glance/
  7. National Cancer Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; NCI Dictionary of Cancer Terms: hematocrit; [cited 2017 Feb 20]; [about 3 screens]. Available from: https://www.cancer.gov/publications/dictionaries/cancer-terms?cdrid=729984
  8. National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Types of Blood Tests; [updated 2012 Jan 6; cited 2017 Feb 20]; [about 5 screens]. Available from: https://www.nhlbi.nih.gov/health/health-topics/topics/bdt/types
  9. National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; What Are the Risks of Blood Tests?; [updated 2012 Jan 6; cited 2017 Feb 20]; [about 7 screens]. Available from: https://www.nhlbi.nih.gov/health/health-topics/topics/bdt/risks
  10. National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; What Are the Signs and Symptoms of Anemia?; [updated 2012 May 18; cited 2017 Feb 20]; [about 8 screens]. Available from: https://www.nhlbi.nih.gov/health/health-topics/topics/anemia/signs
  11. National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; What Are the Signs and Symptoms of Polycythemia Vera?; [updated 2011 Mar 1; cited 2017 Feb 20]; [about 8 screens]. Available from: https://www.nhlbi.nih.gov/health/health-topics/topics/poly/signs
  12. National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; What Is Polycythemia Vera?; [updated 2011 Mar 1; cited 2017 Feb 20]; [about 3 screens]. Available from: https://www.nhlbi.nih.gov/health/health-topics/topics/poly
  13. National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; What To Expect with Blood Tests; [updated 2012 Jan 6; cited 2017 Feb 20]; [about 6 screens]. Available from: https://www.nhlbi.nih.gov/health/health-topics/topics/bdt/with
  14. University of Rochester Medical Center [Internet]. Rochester (NY): University of Rochester Medical Center; c2017. Health Encyclopedia: Hematocrit; [cited 2017 Feb 20]; [about 2 screens]. Available from: https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=167&contentid=hematocrit

The medical information provided is for informational purposes only, and is not to be used as a substitute for professional medical advice, diagnosis or treatment. Please contact your health care provider with questions you may have regarding medical conditions or the interpretation of test results.

In the event of a medical emergency, call 911 immediately.