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Hematocrit

HCT

 

Hematocrit is a blood test that measures how much of a person's blood is made up of red blood cells. This measurement depends on the number of and size of the red blood cells.

How the Test is Performed

 

A blood sample is needed.

 

How to Prepare for the Test

 

No special preparation is necessary for this test.

 

How the Test will Feel

 

When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.

 

Why the Test is Performed

 

The hematocrit is almost always done as part of a complete blood count (CBC).

Your health care provider may recommend this test if you have signs of or are at risk for anemia. These ionclude having:

  • Grumpiness or tiredness
  • Headaches
  • Problems concentrating
  • Poor nutrition
  • Heavy menstrual periods
  • Blood in your stools, or vomit (if you throw up)
  • Treatment for cancer
  • Leukemia or other problems in the bone marrow
  • Chronic medical problems, such as kidney disease or certain types of arthritis

 

Normal Results

 

Normal results vary, but in general they are:

  • Male: 40.7% to 50.3%
  • Female: 36.1% to 44.3%

For babies, normal results are:

  • Newborn: 45% to 61%
  • Infant: 32% to 42%

The examples above are common measurements for results of these tests. Normal value ranges vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your provider about the meaning of your specific test results.

 

What Abnormal Results Mean

 

Low hematocrit may be due to:

  • Anemia
  • Bleeding
  • Destruction of red blood cells
  • Leukemia
  • Malnutrition
  • Too little iron, folate, vitamin B12, and vitamin B6 in the diet
  • Too much water in the body

High hematocrit may be due to:

  • Congenital heart disease
  • Failure of the right side of the heart
  • Too little water in the body (dehydration)
  • Low levels of oxygen in the blood
  • Scarring or thickening of the lungs
  • Bone marrow disease that causes abnormal increase in red blood cells

 

Risks

 

Veins and arteries vary in size from one person to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight but may include:

  • Excessive bleeding
  • Fainting or feeling lightheaded
  • Hematoma (blood buildup under the skin)
  • Infection (a slight risk any time the skin is broken)

 

 

References

Chernecky CC, Berger BJ. H. In: Chernecky CC, Berger BJ. Laboratory Tests and Diagnostic Procedures. 6th ed. St. Louis, MO: Elsevier Saunders; 2013:chap H.

Kumar V, Abbas AK, Aster JC. Red blood cell and bleeding disorders. In: Kumar V, Abbas AK, Aster JC, eds. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Philadelphia, PA: Elsevier Saunders; 2015:chap 14.

Maheshwari A, Carlo WA. Blood disorders. In: Kliegman RM, Stanton BF, St Geme JW, Schor NF, eds. Nelson Textbook of Pediatrics. 20th ed. Philadelphia, PA: Elsevier; 2015:chap 103.

 
  • Formed elements of blood

    Formed elements of blood - illustration

    Blood transports oxygen and nutrients to body tissues and returns waste and carbon dioxide. Blood distributes nearly everything that is carried from one area in the body to another place within the body. For example, blood transports hormones from endocrine organs to their target organs and tissues. Blood helps maintain body temperature and normal pH levels in body tissues. The protective functions of blood include clot formation and the prevention of infection.

    Formed elements of blood

    illustration

    • Formed elements of blood

      Formed elements of blood - illustration

      Blood transports oxygen and nutrients to body tissues and returns waste and carbon dioxide. Blood distributes nearly everything that is carried from one area in the body to another place within the body. For example, blood transports hormones from endocrine organs to their target organs and tissues. Blood helps maintain body temperature and normal pH levels in body tissues. The protective functions of blood include clot formation and the prevention of infection.

      Formed elements of blood

      illustration

    A Closer Look

     

      Tests for Hematocrit

       

       

      Review Date: 3/13/2016

      Reviewed By: Laura J. Martin, MD, MPH, ABIM Board Certified in Internal Medicine and Hospice and Palliative Medicine, Atlanta, GA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.

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