CBC Complete blood count, a set of values of the cellular (formed) elements of blood. CBC measurements are usually determined by specially designed machines that analyze the different components of blood in less than a minute. The values generally included in a CBC are the following: The number of white blood cells in a vol-ume of blood. The normal range varies slightly among laboratories but is generally between 4,300 and 10,800 cells per cubic millimeter (cmm). The automated white cell differential,which is a machine-generated percentage of the different types of white blood cells, usually split into granulocytes, lymphocytes, monocytes, eosinophils, and basophils. Red cell count, which is the number ofred blood cells in a volume of blood. The normal range varies slightly among laboratories but is generally between 4.2 and 5.9 million cells/cmm. The amount of hemoglobin in a volumeof blood. The normal range for hemoglobin is different between the sexes; it is approximately 13–18 g/deciliter for men and 12–16 g/deciliter for women (international units 8.1–11.2 millimoles/liter for men and 7.4–9.9 millimoles/liter for women). Hematocrit, the ratio of the volume of redcells to the volume of whole blood. The normal range for hematocrit is different between the sexes and is approximately 45 to 52 percent for men and 37 to 48 percent for women. Mean cell volume, which is the averagevolume of a red cell. This is a calculated value derived from the hematocrit and red cell count, and the normal range is 86–98 femtoliters. Mean cell hemoglobin, which is the aver-age amount of hemoglobin in the average red cell. This is a calculated value that is derived from the measurement of hemoglobin and the red cell count. The normal range is 27–32 picograms. Mean cell hemoglobin concentration,which is the average concentration of hemoglobin in a given volume of red cells. This is a calculated volume that is derived from the hemoglobin measurement and the hematocrit. The normal range is 32 to 36 percent. Red cell distribution width, which is ameasurement of the variability of red cell size. Higher numbers indicate greater variation in size. The normal range is 11–15. Platelet count, which is the number ofplatelets in a volume of blood. Platelets are not complete cells; they are actually fragments of cytoplasm from a cell called a megakaryocyte that is found in the bone marrow. Platelets play a vital role in blood clotting. The normal range varies slightly among laboratories but is in the range of 150,000–400,000/cmm (150×109/liter to 400×109/liter).

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