Iron Deficiency Anemia Diagnosis and Treatment

Diagnostic Criteria

The American College of Physicians recommends that iron deficiency anemia be diagnosed based on laboratory findings, including microcytic hypochromic pattern, elevated RDW, and low serum ferritin, in patients with a clinical picture consistent with iron deficiency 1, 2
A microcytic hypochromic pattern, characterized by MCV <80 fL, MCH <27 pg, and MCHC <32 g/dL, is indicative of iron deficiency anemia 1, 2
An elevated RDW (>14.0%) combined with low MCV strongly distinguishes iron deficiency anemia from thalassemia minor 1, 2
Serum ferritin <45 μg/L provides optimal sensitivity and specificity for iron deficiency 1, 2

The American College of Physicians recommends oral ferrous sulfate 324 mg (65 mg elemental iron) one to three times daily as the first-line treatment for iron deficiency anemia 1, 2
Treatment should continue for at least three months after hemoglobin normalizes to fully replenish iron stores 1, 2
Alternative formulations, such as ferrous gluconate or ferrous fumarate, may be used if gastrointestinal side effects occur 1, 2
Adding ascorbic acid (vitamin C) 200-500 mg with each iron dose enhances absorption 1, 2

Hemoglobin should rise ≥1 g/dL within 2 weeks of starting treatment, confirming iron deficiency as the cause 1, 2
Expect hemoglobin increase of at least 2 g/dL within 4 weeks of starting treatment 1, 2
Monitoring schedule should include checking hemoglobin, hematocrit, MCV, and MCH at 2 weeks, 4 weeks, 3 months, then every 3 months for the first year, then annually 1, 2

Identification of the source of iron loss is critical in patients with iron deficiency anemia, particularly in postmenopausal women 1, 3
Investigation for gastrointestinal blood loss, menstrual blood loss, dietary inadequacy, and malabsorption should be performed 1, 3
Non-menstruating women with hemoglobin <10 g/dL warrant fast-track gastrointestinal referral to exclude malignancy 1, 3

Intravenous iron should be considered if malabsorption is documented, patient cannot tolerate oral iron, ongoing blood loss exceeds oral replacement capacity, or no hemoglobin response after 4 weeks of adequate oral therapy 1, 2, 4
Expected hemoglobin increase with IV iron is at least 2 g/dL within 4 weeks 1, 2

In patients with severe iron‑deficiency anemia (e.g., hemoglobin ≈ 7 g/dL, MCV ≈ 66 fL) who have borderline low serum vitamin B12 (≈ 200 pg/mL) and folate (≈ 4–5 ng/mL), these marginal deficiencies are typically secondary to the iron deficiency and do not require immediate supplementation. 5

Serum vitamin B12 and folate should be re‑measured after approximately three months of adequate oral iron therapy, because levels often return to normal once iron stores are restored. 5

Empiric supplementation of vitamin B12 or folate at the initial stage of treatment is discouraged; priority should be given to iron repletion, with reassessment of the vitamin levels after iron therapy has been established. 5