Macrocytic anemias can be caused by impaired DNA synthesis leading to megaloblastosis, as occurs with Deficiencies of vitamin B12 or folate (see Megaloblastic Macrocytic Anemias) Other causes of macrocytic anemia include Chronic alcohol intake Medications (eg, zidovudine, azathioprine, methotrexate, hydroxyurea, imatinib) or toxins Hemolysis with reticulocytosis Liver disease Myelodysplastic syndromes (MDS) Some patients with hypothyroidism have macrocytic RBC indices, including some without anemia.