bone marrow, or myelodysplasia. In contrast, non-megaloblastic macrocytic anemias associated with a high reticulocyte count (reticulocytosis) may be caused by hemolysis or bleeding. For megaloblastic macrocytic anemias, useful tests may include serum levels of Vitamin B12, methylmalonic acid, and homocysteine. If there is no clear evidence of Vitamin B12 or folic acid deficiency, additional causes of megaloblastic anemia include copper deficiency, medications, and certain inborn errors of metabolism. Epidemiology Macrocytic anemias have several causes but with the implementation of folic acid fortification in North America, folic acid deficiency has become a rare cause of megaloblastic macrocytic anemia in that part of the world. In this region, Vitamin B12 deficiency is a far more common cause of megaloblastic macrocytic anemia. In countries that have not put such practices into place — including most European nations — folic acid deficiency remains a common cause of macrocytic anemia. See also List of circulatory system conditions References External links Anemias