Macrocytic Anemia

Macrocytic anemia refers to macrocytosis (mean corpuscular volume (MCV) greater than 100 fL) in the setting of anemia (hemoglobin less than 12 g/dL or hematocrit (Hct) less than 36% in nonpregnant females, hemoglobin less than 11 g/dL in pregnant females, or hemoglobin less than 13 g/dL or Hct less than 41% in males). It is divided into two forms, megaloblastic (hypersegmented neutrophils) and non-megaloblastic. The megaloblastic form is due to impaired DNA synthesis from folate and/or vitamin B12 deficiencies, while the non-megaloblastic moiety occurs from multiple mechanisms.