Complete blood count

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Complete blood count (CBC) is a blood test often ordered by doctors to assist them in disease diagnosis. The absence or excess in levels of cellular components in the blood help medical professionals determine the patient’s disease. The main portion of the test measures the complete blood count of [white blood cell|white blood cells] (WBC), [red blood cell|red blood cells] (RBC) and [platelet|platelets]. A [medical technology|medical technologist] usually performs the test as required.


How the test is performed

The complete blood count is taken by drawing a teaspoon or two of blood from the vein of the patient via needle and syringe into vacuum containers. These containers are taken to the laboratory for analysis. There are no special requirements to prepare for the test.

Five major components of CBC

  1. White blood cell (WBC) or [leukocyte] count is the amount of infection-fighting cells in the blood. The normal level or range of white blood cell count differs between laboratories but commonly between 4,500 to 10,000 cells per cubic millimeter (cells/mcL) of blood. A differential count comprises of [granulocyte|granulocytes], [monocyte|monocytes], [lymphocyte|lymphocytes], [eosinophil|eosinophils] and [basophil|basophils].
  2. Red blood cell (RBC) or [erythrocyte] count is the amount of oxygen-carrying cells in the blood. The normal range is usually between 4.7 to 6.1 million cells/mcL for males and 4.2 to 5.4 million cells/mcL for females. RBCs are the biggest group of cells in the blood; they are smaller than white blood cells but bigger than platelets.
  3. [Hemoglobin] (HGB) gives RBCs their red color. This is the substance which carries oxygen from the lungs to the other parts of the body and swaps it with carbon dioxide, taking it from the tissues to the lungs. Normal levels vary per altitude.
  4. Hematocrit (HCT) is the proportion in percentage of RBCs in relation to total blood volume.
  5. Platelet – These cells are responsible for forming blood clots in order to stop bleeding. These are measured in thousands per cubic millimeter (m/uL).

Other components of CBC

  • Mean corpuscular volume (MCV) – The average volume of hemoglobin in an average RBC.
  • Mean Corpuscular Hemoglobin (MCH) – The average amount of hemoglobin in the average RBC.
  • Mean Corpuscular Hemoglobin Concentration (MCHC) – The average concentration of hemoglobin in a specified volume of RBCs.
  • Red Cell Distribution Width (RDW) – The measurement of the differences of red cell shape and size.
  • Mean Platelet Volume (MPV) – Average size of platelets in a given blood volume.


There is hardly any risk in having blood taken. Since vein and arterial size vary from one person to the next, drawing blood may be difficult [Fondue Forks for some people. Some may experience light-headedness or [hematoma].


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