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Answers From Experts & Organizations (1)

Internal Medicine
Emory University
131 Answers
108,668 Helpful Votes

RDW stands for the red blood cell distribution width. This is a standard reported measure on a complete blood count (CBC) lab test. It measures the variability in red blood cell size.

In the normal state, red blood cells are continually being produced and removed from the blood at a steady rate. The young, immature red blood cells are larger than mature red blood cells. There are predictable proportions of large and small red blood cells, which can be plotted on a graph as the normal values.

In certain forms of anemia, the RDW may be higher than normal because there are more immature or abnormal red blood cells skewing the statistical range of values.

The RDW result is nonspecific. If a doctor suspects an unusual form of anemia, there are more sophisticated tests that can make the diagnosis.

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