What is red cell distribution width?

Red cell distribution width is a measurement of variation between red blood cells sizes. There should be an even distribution of immature and mature /small and large red blood cells. If that distribution leans to one side or the other, a medical condition could be causing the imbalance.

If the red cell distribution width percentage is abnormal, doctors will compare the results of the test with the mean corpuscular volume to determine a possible cause for the abnormality.

Normal Value Range

• Negative Pregnancy Adult: < 14.5 percent or < 0.145
• Pregnancy Trimester One: 11.7 to 14.9 percent or 0.117 to 0.149
• Pregnancy Trimester Two: 12.3 to 14.7 percent or 0.123 to 0.147
• Pregnancy Trimester Three: 11.4 to 16.6 percent or 0.114 to 0.166

Varying forms of anemia can cause an imbalance in red blood cell size variation. Too many immature red blood cells may be a sign of degenerative anemia; while too many small red blood cells could be a sign of anemia caused by iron deficiency.