CBC

Definition

A complete blood count (CBC) test measures the following:

The CBC test also provides information about the following measurements:

The platelet count is also usually included in the CBC. 

How the Test is Performed

A blood sample is needed. For information on how this is done, see: Venipuncture

How to Prepare for the Test

There is no special preparation needed.

How the Test will Feel

When the needle is inserted to draw blood, you may feel moderate pain, though most people feel only a prick or a stinging sensation. Afterward there may be some throbbing or bruising.

Why the Test is Performed

A complete blood count (CBC) is used to detect or monitor many different health conditions. It may be used to:

Normal Results

Blood counts may vary with altitude. In general, normal results are:

RBC count:

WBC count:

Hematocrit:

Hemoglobin:

Red blood cell indices:

Note:

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

What Abnormal Results Mean

A high RBC or hematocrit may be due to:

A low RBC or hematacrit is a sign of anemia, which can result from:

A lower than normal white blood cell count is called leukopenia. A decreased WBC count may be due to:

High numbers of WBCs is called leukocytosis. It can result from:

Low hemoglobin values may be due to:

Risks

There is very little risk involved with having your blood taken. Veins and arteries vary in size from one patient to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others.

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

Considerations

RBCs transport hemoglobin which, in turn, carries oxygen. The amount of oxygen received by body tissues depends on the amount and function of RBCs and hemoglobin.

WBCs are mediators of inflammation and the immune response. There are various types of WBCs that normally appear in the blood:


Review Date: 3/19/2012
Reviewed By: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, Inc.

This information 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. © 1997- 2007 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.