Macrocytosis is a common laboratuary finding with the increase of mean cell volume of the red blood cells. Although the normal range varies slightly from one laboratory to another, mean cell volume values exceeding 100 femtolitres generally shows the presence of macrocytosis. Macrocytic anemia is due to different causes and the most frequent causes are megaloblastic anemia and alcoholism. Macrocytic anemia split into two groups as megaloblastic and nonmegaloblastic anemia. Neutrophil hypersegmentation and macroovalocytosis on the blood film are the most sensitive and specific for megaloblastic anemia. The red cells are usually round rather than oval and the neutrophil hypersegmentation are not showed in the nonmegaloblastic anemia.