 Chronic blood loss may lead to iron deficiency as a cause for anemia, particularly microcytic anemia (small red blood cells), which can be evaluated with a serum ferritin, iron, total iron-binding capacity and transferrin saturation.Anemia may be due to a complication of treatment from azathioprine, which can cause low blood counts, or sulfasalazine, which can result in folate deficiency.Thiopurine metabolites (from azathioprine) and a folate level can help.