What does elevated rdw on hematicrit mean?

Random Dist Width: Random distribution width (RDW) is a measure of the variability of the sizes (volume) of the red blood cells in a complete blood count. The lower the number, the more similar are the sizes of the red cells. The higher the rdw, the more variable are the red cells in sizes (from small to large). The variability in red cell sizes can sometimes help narrow down the causes of anemia in a patient.