What is the red blood cell (RBC) count?

The red blood cells (RBCs or erythrocytes) are the most common type of cells in the blood. We each have millions and millions of these little disc-shaped cells. The RBC count is done to determine if the number of red blood cells is low (anemia) or high (polycythemia).

In an RBC count, the number and size of the RBCs are determined. This is usually reported as number of RBCs per a specified volume, typically in millions of RBC's in micro-liters (one one-thousandth of an ml) of whole blood. The shape of the red blood cells is also evaluated under a microscope. All of this information, the number, size and shape of the RBCs, is useful in the diagnosis of anemia. Further, the specific type of anemia may be determined by this information.