What is the primary treatment for iron deficiency anaemia in adults?

Treatment of Iron Deficiency Anaemia in Adults

Oral iron replacement with ferrous sulfate 325 mg (65 mg elemental iron) once daily is the primary treatment for iron deficiency anaemia in most adults, with treatment continued for 3 months after haemoglobin normalisation to replenish iron stores. 1, 2

First-Line Oral Iron Therapy

Start with one tablet daily of ferrous sulfate, fumarate, or gluconate taken in the morning on an empty stomach. 1 Each ferrous sulfate 325 mg tablet contains 65 mg elemental iron. 3

• If not tolerated, reduce to alternate-day dosing (one tablet every other day) rather than stopping treatment, as this maintains similar iron absorption while reducing gastrointestinal side effects. 1, 4
• Recent evidence shows that alternate-day dosing with 60-120 mg elemental iron may optimize fractional iron absorption by allowing hepcidin levels to subside between doses. 4
• Adding vitamin C (ascorbic acid) enhances iron absorption. 2

Monitoring Response to Oral Iron

• Check haemoglobin at 4 weeks to confirm response—expect a rise of ≥10 g/L within 2 weeks or 2 g/dL after 3-4 weeks. 1, 2
• Continue treatment for 3 months after haemoglobin normalises to replenish body iron stores. 1, 5, 2
• Monitor haemoglobin and MCV every 3 months for the first year, then every 6-12 months thereafter to detect recurrence. 1, 5, 2

Failure to Respond to Oral Iron

If haemoglobin fails to rise adequately after 4 weeks, consider:

• Poor compliance (most common cause). 2
• Ongoing blood loss exceeding absorption capacity. 5
• Malabsorption (celiac disease, atrophic gastritis, inflammatory bowel disease, post-bariatric surgery). 1, 2
• Misdiagnosis (anaemia of chronic disease rather than true iron deficiency). 5

Intravenous Iron Therapy

Parenteral iron should be used when oral iron is contraindicated, ineffective, or not tolerated. 1

Specific Indications for Intravenous Iron

• Chronic heart failure: Intravenous iron has demonstrated prognostic benefit in meta-analyses, whereas oral iron shows no prognostic benefit and is poorly absorbed due to gut oedema. 1
• Chronic kidney disease: Intravenous iron is required once dialysis commences or if oral iron is ineffective in predialysis patients. 1
• Inflammatory bowel disease: Indicated for moderate to severe anaemia (Hb <100 g/L) or intolerance to oral iron. 1
• Ongoing blood loss exceeding intestinal absorption capacity (e.g., large hiatus hernias with Cameron lesions). 5
• Malabsorption syndromes: Celiac disease, post-bariatric surgery, atrophic gastritis. 1, 6
• Second and third trimesters of pregnancy. 6
• Oral iron intolerance with significant gastrointestinal side effects. 1, 6

Alternative Oral Preparations

If traditional iron salts (ferrous sulfate, fumarate, gluconate) cause intolerable side effects:

• Ferric maltol may be considered for patients with inactive inflammatory bowel disease and moderate anaemia (Hb >95 g/L), normalising haemoglobin in 63-66% at 12 weeks. 1
• Liquid preparations may be better tolerated than tablets. 2

Critical Pitfalls to Avoid

• Do not defer iron replacement therapy while awaiting investigations unless colonoscopy is imminent. 1
• Do not stop investigating after finding one cause—multiple causes frequently coexist (e.g., celiac disease with concurrent gastrointestinal malignancy). 2, 7
• Serum ferritin may be falsely normal in inflammatory conditions (acts as acute phase reactant)—use transferrin saturation <20% or ferritin threshold of 100 μg/L in the presence of inflammation. 1, 7
• In chronic heart failure, avoid oral iron—use intravenous iron instead due to poor absorption and lack of prognostic benefit. 1

Investigation of Underlying Cause

All adults with iron deficiency anaemia require investigation of the underlying cause, particularly those over age 50. 1, 2

• Bidirectional endoscopy (gastroscopy with small bowel biopsy and colonoscopy) is mandatory for men and postmenopausal women, as approximately one-third have underlying gastrointestinal pathology, with one-third of these being malignancy. 1, 2, 7
• Celiac disease serology (tissue transglutaminase antibody) should be checked, accounting for 2-5% of cases. 5, 2, 7
• Consider capsule endoscopy if anaemia persists after negative bidirectional endoscopy, with diagnostic yield of 66.6% in recurrent iron deficiency anaemia. 5