Skip to main content

Health Encyclopedia

Search the Health Encyclopedia

Hematocrit

Definition

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.

Alternative Names

HCT

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.

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.

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997-A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

adam.com

The Agency for Health Care Administration (Agency) and this website do not claim the information on, or referred to by, this site is error free. This site may include links to websites of other government agencies or private groups. Our Agency and this website do not control such sites and are not responsible for their content. Reference to or links to any other group, product, service, or information does not mean our Agency or this website approves of that group, product, service, or information.

Additionally, while health information provided through this website may be a valuable resource for the public, it is not designed to offer medical advice. Talk with your doctor about medical care questions you may have.

Health
Outcome Data

No data available for this condition/procedure.

Health Encyclopedia

More Features

We Appreciate Your Feedback!
1. Did you find this information useful?
         Yes
         No
2. Would you recommend this website to family and friends?
         Yes
         No