The complete blood count (CBC) is a screening test, used to diagnose and manage numerous diseases. It can reflect problems with fluid volume (such as dehydration) or loss of blood. It can show abnormalities in the production, life span, and destruction of blood cells. It can reflect acute or chronic infection, allergies, and problems with clotting.
The CBC test isolates and counts the 7 types of cells found in the blood: neutrophil, eosinophil, basophil, red blood cell, lymphocyte, monocyte, and platelet.
A CBC requires a small blood specimen. Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand.
Preparation: The skin should be cleaned with alcohol or iodine before the test. The patient should be seated comfortably or reclining.
How the test will feel:
When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. After the blood is drawn, there may be some throbbing.
Although the CBC test is very safe, any blood drawing has a slight risk of complication, including:
Normal values vary with altitude and gender.
What abnormal results may mean:
Low numbers of red blood cells may indicate anemia, which has many causes including:
Low numbers of white blood cells (leukopenia) may indicate:
High numbers of white blood cells (leukocytosis) may indicate:
A high hematocrit may indicate:
High numbers of red blood cells may indicate:
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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