Complete Blood Count (CBC)

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What is the complete blood count test (CBC)?

The complete blood count (CBC) is one of the most commonly ordered blood tests. The complete blood count is the calculation of the cellular (formed elements) of blood. These calculations are generally determined by special machines that analyze the different components of blood in less than a minute.

A major portion of the complete blood count is the measure of the concentration of white blood cells, red blood cells, and platelets in the blood.

How is the complete blood count test (CBC) done?

The complete blood count (CBC) test is performed by obtaining a few milliliters (one to two teaspoons) of blood sample directly form the patient. It can be done in many settings including the doctor's office, laboratories, and hospitals. The skin is wiped clean with an alcohol pad, and a needle is inserted through the area of cleansed skin into to patient's vein (one that can be visualized from the skin.) The blood is pulled from the needle by a syringe or by a connection to a special vacuumed vial where it is collected. This sample is taken to the laboratory for analysis.

What are the components of the complete blood count (CBC)?

The complete blood count, or CBC, lists a number of many important values. Typically, it includes the following:

  • White blood cell count (WBC or leukocyte count)
  • WBC differential count
  • Red blood cell count (RBC or erythrocyte count)
  • Hematocrit (Hct)
  • Hemoglobin (Hbg)
  • Mean corpuscular volume (MCV)
  • Mean corpuscular hemoglobin (MCH)
  • Mean corpuscular hemoglobin concentration (MCHC)
  • Red cell distribution width (RDW)
  • Platelet count
  • Mean Platelet Volume (MPV)
Medically Reviewed by a Doctor on 1/24/2014

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Complete Blood Count - Diagnosis Question: What was your complete blood count (CBC) test used for?
Complete blood count (CBC) is a blood test used to assist in diagnosing certain diseases and conditions.

What Does a High White Platelet Count Mean?

Medical Author: Benjamin Wedro, MD, FAAEM
Medical Editor: Melissa Conrad Stöppler, MD

Viewer Question: What are some of the potential diagnoses when a person has a high platelet count? (Platelet count approximately 420?)

Dr. Stöppler's Response: Platelets are the smallest cell-like structures in the bloodand are important for blood clotting and plugging damaged blood vessels. Platelet countsare usually done by laboratory machines that also count other blood elements such as the white and red cells. Normal platelet counts are in the range of 150,000 to 400,000 per microliter (or 150 - 400 x 109 per liter), but the normal rangefor the platelet count varies slightly among different laboratories.