What is the specific treatment for iron‑deficiency anemia in non‑pregnant adults?

Treatment of Iron Deficiency Anemia in Non-Pregnant Adults

First-Line Oral Iron Therapy

Start ferrous sulfate 200 mg (65 mg elemental iron) once daily immediately upon diagnosis—this is the gold-standard, most cost-effective treatment with proven efficacy. 1, 2

• Take the dose on an empty stomach in the morning for maximal absorption, though taking with food is acceptable if gastrointestinal side effects occur. 1, 2
• Add vitamin C 500 mg with each iron dose to markedly enhance absorption, especially critical when transferrin saturation is severely low. 1, 2
• Never prescribe multiple daily doses—hepcidin remains elevated for 48 hours after iron intake, blocking subsequent absorption by 35-45% and increasing side effects without improving efficacy. 1, 2
• Avoid tea and coffee within 1 hour of the iron dose, as these strongly inhibit absorption. 1

Alternative Oral Formulations

• If ferrous sulfate is not tolerated, switch to ferrous fumarate (106 mg elemental iron) or ferrous gluconate (38 mg elemental iron)—all ferrous salts have equivalent efficacy and tolerability. 1, 2
• Avoid modified-release preparations—they release iron beyond the duodenum and are classified as "less suitable for prescribing." 2
• Do not use multivitamin preparations as the sole iron source; they contain insufficient elemental iron (≤14 mg) for treating anemia. 2

Alternate-Day Dosing Option

• If daily dosing causes intolerable gastrointestinal side effects, switch to alternate-day dosing with 100-200 mg elemental iron—this markedly increases fractional absorption and reduces side effects while maintaining efficacy. 1, 2

Expected Response and Monitoring

Check hemoglobin at 2-4 weeks; expect a rise of approximately 2 g/dL (≥10 g/L). 1, 2, 3

• A hemoglobin rise <10 g/L at 2 weeks predicts treatment failure with 90.1% sensitivity and 79.3% specificity—this signals the need to switch to intravenous iron. 2, 3
• Continue oral iron for 3 months after hemoglobin normalizes to fully replenish iron stores; total treatment duration is typically 6-7 months. 1, 2
• Monitor hemoglobin and red-cell indices every 3 months during the first year, then again after another year. 1

When to Switch to Intravenous Iron

Switch to IV iron when oral therapy fails or is contraindicated—do not persist with ineffective oral iron beyond 4 weeks. 1, 4

Absolute Indications for IV Iron

• Intolerance to at least two different oral iron preparations (e.g., ferrous sulfate and ferrous fumarate or gluconate). 1, 5, 6
• Active inflammatory bowel disease with hemoglobin <10 g/dL—inflammation-driven hepcidin markedly impairs oral absorption and oral iron may worsen inflammation. 1, 6
• Post-bariatric surgery patients—duodenal absorption is anatomically disrupted. 1, 6
• Ferritin fails to improve after 4 weeks of compliant oral therapy despite adequate dosing. 1

Relative Indications for IV Iron

• Celiac disease with inadequate response to oral iron despite strict gluten-free diet adherence. 1, 6
• Chronic kidney disease (non-dialysis dependent) with functional iron deficiency. 1, 5, 6
• Chronic heart failure with iron deficiency (ferritin <100 ng/mL or 100-300 ng/mL with transferrin saturation <20%) to improve exercise capacity. 1, 5, 6
• Ongoing gastrointestinal blood loss exceeding oral replacement capacity. 1
• Need for rapid correction of severe symptomatic anemia with circulatory compromise. 1, 7

Preferred Intravenous Iron Formulations

Choose IV iron products that can replenish the iron deficit in 1-2 infusions to minimize risk and improve convenience. 1, 7

• Ferric carboxymaltose: 750-1000 mg per 15-minute infusion; two doses ≥7 days apart provide 1500 mg total. 1, 5, 7
• Ferric derisomaltose: 1000 mg as a single infusion. 1, 7
• Avoid iron dextran as first-line—it carries a higher anaphylaxis risk (0.6-0.7%), though true anaphylaxis with any IV iron is rare. 1, 7
• Most infusion reactions are complement-activation pseudo-allergies that respond to slowing the infusion rate, not true anaphylaxis. 1, 7
• All IV iron must be administered in a setting equipped with resuscitation equipment. 1, 7

Diagnostic Workup for Underlying Cause

All adult men and post-menopausal women with iron deficiency anemia require bidirectional endoscopy (upper endoscopy + colonoscopy) to exclude gastrointestinal malignancy. 1

• Perform upper endoscopy with small-bowel biopsies to screen for celiac disease, which affects 2-3% of iron-deficiency patients. 1
• Test for Helicobacter pylori and eradicate when positive in patients with recurrent iron deficiency. 1

Premenopausal Women

• Assess menstrual blood loss first—menorrhagia, pregnancy, and breastfeeding account for iron deficiency in 5-10% of menstruating women. 1
• Screen for celiac disease with tissue transglutaminase IgA antibodies; celiac disease is present in 3-5% of iron-deficiency cases. 1
• Reserve endoscopy for women ≥50 years old, those with gastrointestinal symptoms, alarm features, family history of colorectal cancer, or failure to respond to oral iron after 8-10 weeks. 1

Critical Pitfalls to Avoid

• Do not prescribe multiple daily doses—this increases side effects without improving efficacy due to hepcidin-mediated absorption blockade. 1, 2
• Do not stop iron therapy when hemoglobin normalizes—continue for 3 months to replenish stores. 1, 2
• Do not persist with oral iron beyond 4 weeks without a hemoglobin rise—reassess for malabsorption, ongoing loss, or need for IV iron. 1, 3
• Do not overlook vitamin C supplementation when oral iron response is suboptimal. 1, 2
• Do not fail to identify and treat the underlying cause of iron deficiency while providing supplementation. 1
• Do not use oral iron in active IBD patients with hemoglobin <10 g/dL—IV iron is the appropriate first-line option. 1
• Do not delay endoscopic evaluation in high-risk patients (age ≥50, alarm symptoms, or treatment failure), as gastrointestinal malignancy may present solely with iron deficiency. 1