How should I manage a patient with iron‑deficiency anemia (Ferritin 12 ng/mL, Transferrin 382 mg/dL, Total iron‑binding capacity 438 µg/dL, Serum iron 95 µg/dL, Iron saturation 22%)?

Management of Iron-Deficiency Anemia with Ferritin 12 ng/mL

This patient has absolute iron deficiency anemia requiring iron supplementation and mandatory gastrointestinal investigation to exclude malignancy as the underlying cause. 1

Diagnostic Confirmation

Your patient's laboratory values confirm absolute iron deficiency:

• Ferritin 12 ng/mL is diagnostic of iron deficiency – values <15 ng/mL (or <30 ng/mL by most modern criteria) definitively establish depleted iron stores in the absence of inflammation. 1
• Transferrin saturation of 22% falls just above the <20% threshold but combined with the low ferritin confirms true iron deficiency rather than functional deficiency. 1, 2
• Elevated transferrin (382 mg/dL) and TIBC (438 µg/dL) reflect the body's compensatory attempt to capture more iron when stores are depleted. 2
• The serum iron of 95 µg/dL is misleadingly "normal" but must be interpreted in context – serum iron alone is unreliable due to diurnal variation and should never be used in isolation. 2

Mandatory Investigation for Underlying Cause

Gastrointestinal blood loss is the most common cause of iron deficiency in men and postmenopausal women, and occult malignancy must be excluded. 1

Required Evaluations:

• Upper endoscopy with duodenal biopsies – 30-50% of patients will have an upper GI source identified; duodenal biopsies are mandatory to screen for celiac disease, which causes iron deficiency in 2-3% of cases. 1
• Colonoscopy – particularly important if the patient is >50 years old, as 9% of elderly patients with iron deficiency have gastrointestinal cancer. 1, 3
• Medication review – document and discontinue NSAIDs, aspirin, and anticoagulants whenever possible, as these are common contributors to occult GI blood loss. 1
• Dietary assessment – identify iron-deficient diets, but do not presume dietary insufficiency as the sole cause without completing full GI investigation. 1

The British Society of Gastroenterology emphasizes that even with a positive dietary history, full GI investigation is still required because borderline deficient diets are common but rarely the sole explanation. 1

Iron Replacement Strategy

First-Line: Oral Iron

Oral iron is the appropriate initial therapy for this patient with absolute iron deficiency and no inflammatory condition. 1, 4

• Ferrous sulfate 325 mg daily or on alternate days is the standard regimen. 4
• Alternate-day dosing improves absorption and reduces gastrointestinal side effects (constipation, diarrhea, nausea) compared with daily dosing. 2
• Expect hemoglobin to rise by 1-2 g/dL within 4 weeks if the patient is absorbing iron and bleeding has stopped. 1, 2, 3

When to Switch to Intravenous Iron

Consider IV iron if any of the following apply:

• Gastrointestinal intolerance to oral iron (nausea, constipation). 2
• No hemoglobin response after 8-10 weeks of adequate oral therapy, suggesting malabsorption or ongoing blood loss. 2
• Documented malabsorption (celiac disease, post-bariatric surgery, inflammatory bowel disease). 2, 4
• Ongoing blood loss that exceeds oral replacement capacity. 2

Intravenous formulations include ferric carboxymaltose (1,000 mg over 15 minutes), iron sucrose, or low-molecular-weight iron dextran. 2, 5

Monitoring Response

• Recheck complete blood count in 4 weeks after starting oral iron. 1, 3
• If hemoglobin rises by ≥10 g/L (1 g/dL) within 2 weeks, this confirms iron deficiency even if initial iron studies were equivocal. 1
• If hemoglobin does not increase after 4 weeks, consider three possibilities: malabsorption of oral iron, continued bleeding, or an unidentified lesion requiring further investigation. 3
• Do not recheck iron parameters within 4 weeks of IV iron infusion because circulating iron interferes with assays and produces falsely elevated results; the optimal re-assessment window is 4-8 weeks after the last IV dose. 2

Target Iron Parameters After Repletion

• Ferritin ≥30-45 ng/mL in patients without chronic inflammatory conditions. 2
• Transferrin saturation ≥20% to ensure adequate iron availability for erythropoiesis. 2

Common Pitfalls to Avoid

• Do not rely on serum iron alone – it has high intra-individual variability and normal values do not exclude iron deficiency. 2
• Do not skip GI investigation even if dietary insufficiency is identified – occult malignancy must be ruled out in adults. 1
• Do not assume oral iron failure means the patient is non-compliant – consider malabsorption, ongoing blood loss, or the need for IV iron. 2
• Do not measure iron studies too early after IV iron – wait at least 4 weeks to avoid falsely elevated results. 2