As discussed earlier, the RDW indicates the variation in the size of RBCs in the blood sample. A normal RDW indicates a homogenous population of RBCs, meaning the cells are similar in size. The RDW does not necessarily suggest that the cells are normocytic but rather that they are homogenous. When the peripheral smear is examined, the population's RBCs will generally be similar, as seen in the top image on the right.
An increase in RDW indicates that the red cell population is not homogenous. When the peripheral smear is evaluated, the observations should include variation in RBC sizes (heterogeneous population), as seen in the bottom image on the right.
