Iron Deficiency Anemia Diagnosis and Treatment

Diagnostic Considerations

If TSAT is >45-50% or ferritin is markedly elevated, the patient may have iron overload, anemia of chronic disease, or hemolytic anemia, rather than iron deficiency, and giving iron to these patients can cause cirrhosis, diabetes, cardiomyopathy, and arthropathy 1, 2
Serum ferritin is the single most useful marker for iron deficiency anemia and should be obtained prior to investigation and treatment, as it helps distinguish between absolute and functional iron deficiency 3

Insurance will mandate documented ferritin <30 ng/mL OR TSAT <20% before authorization for IV iron therapy, which is indicated for patients who cannot tolerate oral iron, have malabsorption, or have chronic inflammatory conditions 3

Iron studies can distinguish between absolute iron deficiency (TSAT <20%, ferritin <30 ng/mL) and functional iron deficiency (TSAT 20-50%, ferritin 30-800 ng/mL), which have different treatment approaches, with absolute iron deficiency typically treated with oral or IV iron monotherapy, and functional iron deficiency potentially requiring IV iron with or without ESA therapy 4, 5

If hemoglobin hasn't increased by 1-2 g/dL after one month of oral iron, the differential diagnosis includes malabsorption of oral iron, continued occult bleeding, wrong diagnosis, or non-compliance, and iron studies can help identify the cause 1, 3, 5