What is the appropriate treatment for an adult patient with iron deficiency anemia, characterized by hypoferritinemia, elevated TIBC, and low transferrin saturation?

Treatment of Iron Deficiency Anemia

Start oral iron supplementation immediately with ferrous sulfate 324 mg daily (containing 65 mg elemental iron) while simultaneously pursuing diagnostic workup to identify the underlying cause. 1, 2, 3

Immediate Treatment Approach

Initiate oral iron therapy without delay at a dose of 100-200 mg elemental iron daily, typically given as ferrous sulfate 324 mg once daily. 1, 2, 3 Your patient's labs (iron 34, TIBC 243, transferrin saturation 14%) confirm absolute iron deficiency requiring both treatment and investigation. 2

• Take iron on an empty stomach for optimal absorption, though some patients tolerate it better with meals. 1
• Adding 500 mg vitamin C with the iron dose enhances absorption even in the presence of calcium or fiber. 1
• Taking iron with meat protein further improves absorption. 1

Monitoring Response

Reassess hemoglobin after 2-4 weeks of therapy to determine if oral iron is adequate. 2

• A hemoglobin rise ≥1.0 g/dL (10 g/L) within 2 weeks indicates successful oral iron absorption and confirms absolute iron deficiency. 2, 4
• If hemoglobin increases <1.0 g/dL at day 14, transition to intravenous iron as this predicts failure of oral therapy (sensitivity 90.1%, specificity 79.3%). 4
• Repeat complete iron studies after 8-10 weeks, not earlier, as ferritin levels are falsely elevated immediately after iron infusion. 1

When to Use Intravenous Iron

Switch to IV iron if any of the following apply: 1, 2

• Intolerance to oral iron (nausea, abdominal pain, constipation are common)
• Malabsorption conditions (celiac disease, inflammatory bowel disease)
• Ongoing blood loss exceeding intestinal absorption capacity
• Chronic inflammatory conditions where oral iron is ineffective
• Inadequate hemoglobin response (<1.0 g/dL rise) at 2 weeks

Ferric carboxymaltose is the best-studied IV formulation, allowing rapid administration of large single doses (up to 1 gram elemental iron over 15 minutes). 1

Mandatory Diagnostic Workup

Do not delay investigation while awaiting response to iron therapy, especially in men or postmenopausal women, as this may miss gastrointestinal malignancy. 2

Essential investigations include: 1, 2

• Celiac disease screening (present in 3-5% of IDA cases) via serology or small bowel biopsy at gastroscopy
• Bidirectional endoscopy (gastroscopy and colonoscopy) as first-line GI investigation for men and postmenopausal women
• Urinalysis or urine microscopy to exclude urinary blood loss
• Dietary assessment for inadequate iron intake, particularly in vegetarians or restrictive eating patterns
• Menstrual history in premenopausal women (though severe anemia warrants investigation regardless)

Risk stratification: 1, 2

• Men with hemoglobin <110 g/L or postmenopausal women with hemoglobin <100 g/L warrant fast-track urgent GI evaluation
• The threshold for investigating non-anemic iron deficiency should be low in men, postmenopausal women, and those with GI symptoms or family history of GI pathology

Common Pitfalls to Avoid

• Never assume dietary deficiency alone without excluding pathologic causes, especially in men and postmenopausal women. 2
• Do not supplement iron if ferritin is normal or elevated (>150 μg/L), as this is potentially harmful and suggests anemia of chronic disease rather than true iron deficiency. 1
• Avoid increasing oral iron doses beyond 200 mg elemental iron daily, as gastrointestinal side effects worsen without improving absorption due to tight intestinal regulation. 1
• Recent evidence suggests alternate-day dosing may improve absorption with fewer adverse effects compared to daily dosing. 1