Red Cell Distribution Width (RDW)

What Does Red Cell Distribution Width (RDW) Mean?

Red cell distribution width (RDW) refers to the variation in the size of red blood cells within a particular specimen. The determination of RDW is made using an RDW test, often as part of a complete blood count (CBC) test. Normal red blood cells average between 6 and 8 micrometers in diameter. Cells that are larger or smaller than this average may be indicative of an underlying health condition.


WorkplaceTesting Explains Red Cell Distribution Width (RDW)

Red cell distribution width is calculated based on the deviation of the cells from the standard size. A higher level of deviation results in a higher RDW level. A high RDW, which indicates that the blood cells have a greater variation in size, whether larger or smaller than normal, is called anisocytosis.

When a person's red blood cells are unequal in size, as determined by assessing the RDW, this may indicate that his or her blood cell production, or erythropoiesis, is impaired. Conditions that may be diagnosed in part through the use of an RDW test include anemia, inflammation, malnutrition, kidney disease, clotting disorders or cardiovascular diseases, diabetes, liver disease, and cancer.


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