How should I manage an 11-year-old boy with iron deficiency anemia (serum iron ~20 µg/dL, transferrin saturation ~7%)?

Management of Severe Iron Deficiency in an 11-Year-Old Boy

Start oral ferrous sulfate 3–6 mg/kg/day of elemental iron immediately, divided into 1–2 doses, and investigate the underlying cause of iron deficiency while monitoring response at 2–4 weeks. 1

Understanding the Laboratory Results

Your patient has severe iron deficiency with iron-deficient erythropoiesis:

• A serum iron of 20 µg/dL is markedly reduced, confirming inadequate circulating iron for red blood cell production 1
• A transferrin saturation of 7% is severely low—well below the diagnostic threshold of 10–15% that the World Health Organization uses to define iron deficiency, and far below the 16% cutoff used in adults 2, 1
• A saturation of 4–7% indicates insufficient iron is available for hemoglobin synthesis regardless of ferritin level 1
• The day-to-day variation in serum iron is substantial, but a value this low combined with such severe transferrin saturation confirms true deficiency 2

Essential Diagnostic Work-Up

Before initiating treatment, obtain these studies to identify the cause and assess severity:

• Complete blood count with red cell indices (MCV, MCH) and reticulocyte count to assess anemia severity and confirm microcytic hypochromic pattern 1, 3
• Serum ferritin to quantify iron stores; however, ferritin is an acute-phase reactant and will be falsely elevated by any infection or inflammation 2, 1
• C-reactive protein (CRP) or ESR to identify inflammation that could artificially elevate ferritin from its true depleted state 1
• Erythrocyte protoporphyrin (>80 µg/dL in children aged 1–2 years confirms iron-deficient erythropoiesis) 1
• MCV and RDW to distinguish iron deficiency (low MCV with RDW >14%) from thalassemia trait 1

Identifying the Underlying Cause

Iron deficiency at this age and severity rarely occurs without an identifiable source:

• Dietary insufficiency: Assess intake of heme iron (meat, poultry, fish) and non-heme iron sources; excessive cow's milk intake (>24 oz/day) inhibits iron absorption 1, 3
• Gastrointestinal blood loss: Obtain stool guaiac testing; consider celiac disease screening (affects 3–5% of children with iron deficiency anemia) 4
• Malabsorption disorders: Screen for celiac disease, inflammatory bowel disease, or Helicobacter pylori infection 2, 4
• Increased demand: Rapid growth spurts during adolescence increase iron requirements 3
• Chronic blood loss: Assess for epistaxis, hematuria, or parasitic infections (hookworm in endemic areas) 4

Treatment Strategy

Oral Iron Therapy (First-Line)

• Ferrous sulfate 3–6 mg/kg/day of elemental iron, divided into 1–2 doses 1, 3
• Administer on an empty stomach when possible to maximize absorption (1 hour before or 2 hours after meals), but may give with food if gastrointestinal side effects occur 1
• Avoid giving with milk or calcium-rich foods, as these inhibit iron absorption 1
• Common side effects include constipation, diarrhea, nausea, and dark stools; these can be minimized by starting at lower doses and titrating up 5

Monitoring Response

• Recheck hemoglobin and reticulocyte count at 2–4 weeks to confirm response (expected hemoglobin increase of 1–2 g/dL) 1
• If inflammation was present initially, repeat CRP/ESR and complete blood count to assess resolution 1
• Repeat complete iron panel at 8–10 weeks, not earlier, as ferritin levels remain falsely elevated immediately after treatment 1
• Continue oral iron for 2–3 months after hemoglobin normalizes to replenish iron stores 3

When to Consider Intravenous Iron

Switch to IV iron if any of the following occur:

• Gastrointestinal intolerance to oral iron despite dose adjustments 1, 4
• Lack of hematologic response after 4–8 weeks of adequate oral therapy (hemoglobin fails to rise by 1–2 g/dL) 1, 4
• Documented malabsorption (celiac disease, inflammatory bowel disease) 2, 1
• Ongoing blood loss that exceeds oral replacement capacity 4
• Chronic kidney disease with eGFR <30 mL/min/1.73 m² (unlikely in an 11-year-old but must be excluded) 2, 1

IV iron formulations include ferric carboxymaltose, iron sucrose, and low-molecular-weight iron dextran, which bypass intestinal absorption and directly replenish stores 1, 4

Critical Pitfalls to Avoid

• Do not delay iron supplementation while awaiting complete diagnostic work-up in severe deficiency, as this worsens anemia and impairs growth and neurodevelopment 1, 3
• Do not rely on ferritin alone for diagnosis; it is falsely elevated by infection, inflammation, or chronic disease, masking true iron depletion 2, 1
• Do not dismiss iron deficiency based on "normal" serum iron; serum iron has high day-to-day variability and poor diagnostic accuracy compared to transferrin saturation and ferritin 2, 4
• Do not stop iron therapy once hemoglobin normalizes; continue for 2–3 months to replenish iron stores and prevent recurrence 3
• Do not overlook dietary counseling: Increase heme and non-heme iron intake, limit cow's milk to <24 oz/day, and avoid tea/coffee with meals 1, 3

Neurodevelopmental Considerations

• When iron deficiency anemia occurs in early childhood and is severe and prolonged, it can result in neurodevelopmental and cognitive deficits that may not be fully reversible even after correction 3
• At 11 years old, prompt treatment is essential to prevent further impact on school performance, attention, and cognitive function 3
• The American Academy of Pediatrics recommends universal screening at approximately 1 year of age, but selective screening should be performed at any age when risk factors are identified 3

Treatment Targets

• Achieve hemoglobin appropriate for age and sex (typically >11.5 g/dL for children aged 5–11 years) 3
• Target transferrin saturation ≥20% to ensure adequate iron availability for erythropoiesis 1, 4
• Aim for ferritin ≥30 ng/mL (in absence of inflammation) or ≥100 ng/mL (if chronic inflammation present) to ensure sufficient iron stores 4