There are many conditions of or affecting the human hematologic system — the biological system that includes plasma, platelets, leukocytes, and erythrocytes, the major components of blood and the bone marrow. An anemia is a decrease in number of red blood cells (RBCs) or less than the normal quantity of hemoglobin in the blood.However, it can include decreased oxygen-binding ability of each hemoglobin molecule due to deformity or lack in numerical development as in some other types of hemoglobin deficiency. Anemia is the most common disorder of the blood. There are several kinds of anemia, produced by a variety of underlying causes. Anemia can be classified in a variety of ways, based on the morphology of RBCs, underlying etiologic mechanisms, and discernible clinical spectra, to mention a few. The three main classes of anemia include excessive blood loss (acutely such as a hemorrhage or chronically through low-volume loss), excessive blood cell destruction (hemolysis) or deficient red blood cell production (ineffective hematopoiesis).