Iron deficiency is the most common reason for EPO not working. Iron forms an important part of the chemical structure of hemoglobin. EPO treatment causes the body's iron stores to be used up more quickly than usual.

To find out how much iron is in your body, a test is carried out to measure the level of a substance called ferritin in the blood. The ferritin level should be at least 200 milligrams per liter (200 mg/L) of blood.

Iron deficiency can sometimes be treated with iron tablets such as ferrous sulphate.

You may need regular iron injections. Your doctor or renal nurse administers these at the renal unit.