What is the best course of treatment for a 15-year-old female patient with iron deficiency anemia, characterized by a low serum iron level and high Total Iron Binding Capacity (TIBC)?

Treatment of Iron Deficiency Anemia in a 15-Year-Old Female

Start oral iron supplementation immediately with ferrous sulfate 324 mg daily (containing 65 mg elemental iron) while pursuing diagnostic workup to identify the underlying cause of iron loss. 1, 2

Diagnostic Confirmation

The laboratory values confirm iron deficiency anemia:

• Transferrin saturation = 11% (calculated as 50/450 × 100), which is well below the diagnostic threshold of <16% used to confirm iron deficiency 3
• The elevated TIBC of 450 mg/dL indicates depleted iron stores, as TIBC increases when serum iron and stored iron are low 3
• These findings are consistent with absolute iron deficiency requiring both treatment and investigation 3

Immediate Treatment Approach

Initiate oral iron therapy without delay:

• Ferrous sulfate 324 mg tablets once daily, providing 65 mg of elemental iron (362% of the U.S. RDI) 1, 2
• A daily dose of 100-200 mg elemental iron is recommended, with lower doses if side effects occur 4
• Treatment duration typically requires 3-6 months to normalize hemoglobin and replenish iron stores 4

Monitor response to therapy:

• Reassess hemoglobin after 2-4 weeks of treatment 1
• An adequate response (Hb rise ≥10 g/L within 2 weeks) confirms absolute iron deficiency even if initial iron studies were equivocal 3, 1

Mandatory Investigation for Underlying Cause

In a 15-year-old female, the diagnostic workup must focus on:

• Menstrual history: Heavy menstrual bleeding is the most common cause in adolescent females, but this alone should not preclude further evaluation if anemia is severe 3, 1
• Dietary assessment: Evaluate for inadequate iron intake, particularly in vegetarians or those with restrictive eating patterns 3
• Celiac disease screening: Perform transglutaminase antibody (IgA type) and total IgA testing, as celiac disease is present in 3-5% of IDA cases and causes malabsorption 1, 4
• Gastrointestinal blood loss: Consider stool guaiac testing for occult blood to evaluate for GI bleeding 3

Bidirectional endoscopy is not routinely required in premenopausal women under 40 years of age unless there are red flags (involuntary weight loss, abdominal pain, elevated inflammatory markers, or failure to respond to iron therapy) 1, 4

When to Consider Intravenous Iron

Switch to IV iron if:

• Intolerance to oral iron develops (gastrointestinal side effects) 3, 1
• Malabsorption is documented (e.g., confirmed celiac disease with active inflammation) 3, 4
• Inadequate response after 4-6 weeks of adequate oral therapy 5, 6
• Active inflammatory conditions compromise iron absorption 3

Critical Pitfalls to Avoid

• Do not assume dietary deficiency alone: Even in adolescent females, investigate for pathologic causes, especially if anemia is moderate to severe 1
• Do not delay iron supplementation: Begin treatment immediately while pursuing diagnostic workup 1
• Do not overlook celiac disease: This is a frequently missed cause of iron deficiency that requires specific management beyond iron replacement 1, 4
• Do not stop investigation if initial response to iron is good: In cases with severe anemia or concerning features, complete the diagnostic evaluation 1