Anemia associated with a mean red cell volume (MCV) that is higher than the normal range is frequently encountered. Some patients will also have multiple cytopenias. Vitamin B12 and folate deficiency are common causes of megaloblastic anemia and easily treated if distinguished from other bone marrow failure syndromes or microangiopathy. Elevated serum methylmalonic acid values confirm B12 deficiency, and elevated homocysteine is seen in either B12 or folate deficiency.