Absolute vs Functional Iron Deficiency

Iron deficiency may be categorized either as absolute or functional10,11

Absolute iron deficiency refers to the depletion of iron stores
and low or absent stainable iron in the bone marrow11-13
  • Can be defined as serum ferritin <100 ng/mL and transferrin saturation (TSAT) <20%

  • Occurs when there is insufficient iron available for hemoglobin (Hgb) production
Functional iron deficiency is a problem of supply and demand11,12
  • In these patients, serum ferritin may be elevated, while TSAT may be <20%

  • Functional iron deficiency can be caused by:

    • Erythropoiesis stimulating agents (ESAs) stimulating red blood cell (RBC) production beyond the available supply of iron necessary for Hgb synthesis

    • Chronic inflammation blocking the transfer of stored iron

  • Patients with functional iron deficiency may fail to reach target Hgb levels despite large dosages of ESAs

    • Patients may require more iron to support higher levels of Hgb
Now that you know about Absolute vs Functional IDA, learn more about Iron-responsive Anemia.

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