macrocytosis

the condition in which abnormally large red blood cells ( ERYTHROCYTES ) are present in the blood. It is characteristic of macrocytic anaemias such as those caused by the deficiency of VITAMIN B12 (cyanocobalamin, see also PERNICIOUS ANAEMIA ) and FOLIC ACID . Macrocytes are also produced in those anaemias in which there is an increased rate of production of erythrocytes.