Yep, anemia can be classified into 3 groups based off the MCV, mean corpuscle volume, which is basically the average size of the RBC. Without enough iron, the cells tend to be smaller so that they can maintain a normal concentration of iron in the cell itself. But problems with heme formation, other enzymes deficiencies like G6PD or pyruvate kinase deficiency, can also lead cause anemia.

Another example of anemia with normal sized cells is hemolytic anemia. You have normal cells but they are being broken up either in the blood vessels themselves, or somewhere else such as the spleen. This decreases the available RBC, but each one is still the normal size. Due to having less though, you get less oxygen delivery.

The last type is called macrocytic anemia which is where the RBC are larger than normal. An example is folate (B9) or cobalamin (B12) deficiency. There is not enough of the vitamin available in the cells, so DNA synthesis is impaired. If the synthesis is impaired, cells get arrested in the G2 stage and they are unable to divide and get to a more normal size.