CBC blood test
A complete blood count (CBC) test measures the following:
The CBC test also provides information about the following measurements:
The platelet count is also most often included in the CBC.
Complete blood count; Anemia - CBC
How the Test is Performed
A blood sample is needed.
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. Some people feel only a prick or stinging. Afterward there may be some throbbing or slight bruising. This soon goes away.
Why the Test is Performed
A CBC is a commonly performed lab test. It can be used to detect or monitor many different health conditions. Your health care provider may order this test:
Blood counts may vary with altitude. In general, normal results are:
Red blood cell indices:
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
High RBC, hemoglobin, or hematocrit may be due to:
Low RBC, hemoglobin, or hematocrit 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:
A high WBC count is called leukocytosis. It can result from:
A high platelet count may be due to:
A low platelet count may be due to:
There is very little risk involved with having your blood taken. Veins and arteries vary in size from one person 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:
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:
Bunn HF. Approach to the anemias. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 158.
Costa K. Hematology. In: The Johns Hopkins Hospital; Hughes HK, Kahl LK, eds. The Johns Hopkins Hospital: The Harriet Lane Handbook. 21st ed. Philadelphia, PA: Elsevier; 2018:chap 14.
Vajpayee N, Graham SS, Bem S. Basic examination of blood and bone marrow. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. St Louis, MO: Elsevier; 2017:chap 30.
Review Date: 10/24/2018
Reviewed By: Todd Gersten, MD, Hematology/Oncology, Florida Cancer Specialists & Research Institute, Wellington, FL. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
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