What is the first line of treatment for an adult patient with iron deficiency anemia?

First-Line Treatment for Iron Deficiency Anemia in Adults

Oral iron supplementation with ferrous sulfate, ferrous fumarate, or ferrous gluconate at one tablet daily is the first-line treatment for most adults with iron deficiency anemia. 1

Immediate Initiation of Iron Therapy

• Iron replacement therapy should not be delayed while awaiting diagnostic investigations unless colonoscopy is imminent. 1, 2
• Begin treatment with ferrous sulfate 325 mg (containing 65 mg elemental iron) once daily, or equivalent doses of ferrous fumarate or gluconate. 1, 2
• If oral iron is not tolerated at standard dosing, reduce to one tablet every other day, which maintains efficacy while improving tolerability. 1

When Oral Iron is Appropriate

Oral iron remains first-line therapy for patients who meet ALL of the following criteria:

• Hemoglobin ≥100 g/L (10 g/dL) 1
• Clinically inactive disease (no active inflammation) 1
• No previous intolerance to oral iron 1
• Mild anemia without severe symptoms 1

When to Use Intravenous Iron as First-Line

Intravenous iron should be considered as first-line treatment instead of oral iron in the following situations:

• Hemoglobin <100 g/L (10 g/dL) 1
• Clinically active inflammatory bowel disease 1
• Previous intolerance to oral iron 1
• Chronic kidney disease requiring dialysis 1
• Chronic heart failure with functional iron deficiency 1
• Need for erythropoiesis-stimulating agents 1
• Malabsorption conditions (celiac disease, post-bariatric surgery) 3
• Ongoing significant blood loss 3
• Second or third trimester of pregnancy 3

Monitoring Response

• Check hemoglobin within 4 weeks of starting oral iron therapy. 1
• A hemoglobin rise ≥10 g/L within 2 weeks confirms absolute iron deficiency, even if initial iron studies were equivocal. 1, 2
• Continue iron therapy for approximately 3 months after hemoglobin normalization to replenish iron stores. 1

Critical Caveat: Investigation Cannot Wait

While oral iron is first-line treatment, investigation of the underlying cause must proceed simultaneously, particularly in men and postmenopausal women where gastrointestinal malignancy causes IDA in approximately one-third of cases. 2

• Gastroscopy and colonoscopy should be first-line investigations in men and postmenopausal women with newly diagnosed IDA. 1, 2
• Screen for celiac disease in all patients with IDA (found in 3-5% of cases). 1
• Perform urinalysis to exclude renal tract bleeding. 1

Special Populations Requiring Modified Approach

Inflammatory Bowel Disease: Intravenous iron is superior to oral iron in IBD patients, showing greater efficacy (odds ratio 1.57 for achieving 2 g/dL hemoglobin increase) and better tolerability (odds ratio 0.27 for treatment discontinuation). 1 The European Crohn's and Colitis Organization recommends IV iron as first-line for IBD patients with hemoglobin <10 g/dL. 1

Chronic Heart Failure: Both absolute and functional iron deficiency (ferritin <100 μg/L or transferrin saturation <20%) occur in 40-70% of CHF patients. 1 Intravenous iron improves symptoms and quality of life in this population. 1

Chronic Kidney Disease: Intravenous iron is required once dialysis commences or if oral iron is ineffective in predialysis patients. 1 Management should be coordinated with nephrology. 1