Evaluation of Macrocytic Anemias.

Macrocytic anemia, defined as a mean cell volume (MCV) ≥100 fL in adults, has a narrow differential diagnosis that requires evaluation of the peripheral blood smear as well as additional laboratory testing taken in conjunction with clinical information that includes patient history and physical examination findings. This review is an update on the approach to a patient with macrocytic anemia with attention paid to the differentiation of megaloblastic and non-megaloblastic macrocytic anemias. Critical to the determination of the diagnosis is the judicious use of laboratory testing and the evaluation of those findings in conjunction with the patient medical, surgical, and medication history.