Causes for lack of response to oral iron therapy

A coexisting condition is interfering with bone marrow response to iron repletion

Infection

Inflammatory disorder (eg, rheumatoid arthritis)

Concomitant malignancy

Coexisting folate and/or vitamin B12 deficiency

Bone marrow suppression from another cause

Patient is not iron deficient; possible correct diagnoses include

Thalassemia

Lead poisoning

Anemia of chronic disease/anemia of inflammation

Copper deficiency (zinc toxicity)

Myelodysplastic syndrome/refractory sideroblastic anemia

Patient is not taking the medication

Prescription has not been filled

Prescription has been filled but patient is no longer taking the medication

Medication is being taken but is not being absorbed

Rapid intestinal transport bypasses area of maximum absorption

Enteric coated product: coating is not dissolving

Patient has an acquired condition that causes malabsorption of iron (eg, sprue, atrophic or autoimmune gastritis, Helicobacter pylori infection)

Patient is taking an agent that interferes with absorption (eg, antacids, tetracycline, tea)

Patient has a congenital cause for iron malabsorption (eg, iron-resistant iron deficiency anemia [IRIDA])

Continued blood loss or need in excess of iron dose ingested

Treatable cause of blood loss (eg, bleeding peptic ulcer)

Cause of blood loss that is not treatable (eg, hereditary hemorrhagic telangiectasia [Osler-Weber-Rendu syndrome]) or need cannot be met by oral iron preparation (eg, kidney failure or a malignancy being treated with erythropoietin)

The diagnosis of iron deficiency anemia is generally made when there is hypochromic microcytic red blood cells, low ferritin, and low transferrin saturation (TSAT). Refer to UpToDate for approaches to addressing a lack of response to oral iron that depends on the underlying condition, as well as a discussion of indications for switching to intravenous (IV) iron.

Graphic 56310 Version 5.0

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Causes for lack of response to oral iron therapy