GSTM1 and Iron deficiency anemia: In patients with AID, iron therapy is recommended to be started independently of the actual haemoglobin (Hb) level, while in patients with FID, iron therapy is advised only if patients are symptomatic because of iron deficiency and/or anaemia and should be withheld in patients with high ferritin levels (i.e. > 1000 ng/mL).