What is the recommended treatment for a patient with iron deficiency anemia?

Treatment of Iron Deficiency Anemia

Start with oral ferrous sulfate 200 mg once daily, which is the preferred first-line treatment due to its effectiveness and low cost, and switch to intravenous iron only when specific indications exist. 1

First-Line Oral Iron Therapy

• Prescribe ferrous sulfate 200 mg (containing 65 mg elemental iron) once daily—never multiple times per day. 1
• Once-daily dosing improves gastrointestinal tolerance while maintaining equal or better iron absorption compared to multiple daily doses due to hepcidin regulation that blocks iron absorption for 48 hours after each dose. 1, 2
• No single oral iron formulation has any therapeutic advantage over another—ferrous sulfate is simply the least expensive option. 1
• Alternative formulations (ferrous gluconate or ferrous fumarate) are equally effective if ferrous sulfate causes intolerable side effects, though they cost more without providing superior efficacy or tolerability. 1, 2

Optimizing Oral Iron Absorption

• Add vitamin C (ascorbic acid) 500 mg with each iron dose to enhance absorption, particularly critical when response is suboptimal. 1
• Take iron on an empty stomach for optimal absorption, but taking with food is acceptable if gastrointestinal side effects occur. 1
• If daily dosing causes intolerable side effects, switch to every-other-day dosing, which increases fractional iron absorption and improves tolerance with similar efficacy. 1

Expected Response and Monitoring Protocol

• Hemoglobin should rise by approximately 2 g/dL after 3-4 weeks of treatment. 1
• Check hemoglobin at 4 weeks—failure to rise by 2 g/dL indicates poor compliance, continued blood loss, or malabsorption requiring reassessment. 1
• Continue oral iron for 3 months after hemoglobin normalizes to fully replenish iron stores. 1
• Monitor hemoglobin and red cell indices every 3 months for the first year, then again after another year. 1

Absolute Indications for Intravenous Iron

Switch to IV iron when oral therapy fails or specific conditions exist:

• Intolerance to at least two different oral iron preparations 1
• Active inflammatory bowel disease with hemoglobin <10 g/dL (IV iron is first-line treatment in this scenario) 1
• Post-bariatric surgery patients due to disrupted duodenal absorption mechanisms 1
• Celiac disease with inadequate response to oral iron despite gluten-free diet adherence 1
• Ongoing gastrointestinal blood loss exceeding oral replacement capacity 3
• Chronic kidney disease with functional iron deficiency (ferritin 100-300 ng/mL with transferrin saturation <20%) 1
• Chronic heart failure with iron deficiency (ferritin <100 ng/mL or 100-300 ng/mL with transferrin saturation <20%) to improve symptoms and quality of life 1
• Second and third trimesters of pregnancy when oral iron is insufficient 1, 4

Intravenous Iron Administration

• Prefer IV iron formulations that can replace iron deficits with 1-2 infusions rather than multiple infusions. 1
• Ferric carboxymaltose (Injectafer) is FDA-approved and can deliver 750 mg intravenously in two doses separated by at least 7 days for a total cumulative dose of 1,500 mg per course. 5
• For patients weighing 50 kg or more, ferric carboxymaltose 15 mg/kg body weight up to a maximum of 1,000 mg may be administered as a single-dose per course. 5
• All IV iron formulations have similar overall safety profiles; true anaphylaxis is very rare (0.6-0.7%), with most reactions being complement activation-related pseudo-allergy that responds to slowing the infusion rate. 1
• Check serum phosphate levels in patients requiring repeat IV iron treatment within 3 months, as hypophosphatemia can occur and lead to bone complications. 5

Special Population Considerations

Inflammatory Bowel Disease

• Treat active inflammation first to enhance iron absorption and reduce iron depletion. 1
• Use IV iron as first-line treatment when hemoglobin <10 g/dL with active inflammation. 1

Pregnant Women

• Start oral low-dose iron 30 mg/day at first prenatal visit for prevention. 1
• Treat anemia with 60-120 mg/day elemental iron orally. 1
• Refer pregnant women with hemoglobin <9.0 g/dL for further medical evaluation. 1
• Use IV iron during second and third trimesters if oral iron is insufficient. 1, 4

Post-Bariatric Surgery

• IV iron is preferred due to disrupted duodenal absorption mechanisms. 1

Celiac Disease

• Ensure strict adherence to gluten-free diet to improve iron absorption. 1
• Progress to IV iron if iron stores do not improve despite dietary compliance. 1

Chronic Kidney Disease

• Functional iron deficiency is common, defined by ferritin 100-300 ng/mL with transferrin saturation <20%. 1
• IV iron is preferred for dialysis patients; either IV or oral iron for non-dialysis CKD stages 3-5. 1

Heart Failure

• Screen for iron deficiency with ferritin and transferrin saturation. 1
• IV iron improves symptoms, quality of life, and exercise capacity in heart failure with functional iron deficiency. 1, 5

Critical Pitfalls to Avoid

• Do not prescribe multiple daily doses of oral iron—this increases side effects without improving efficacy due to hepcidin-mediated absorption blockade. 1
• Do not stop iron therapy when hemoglobin normalizes—continue for 3 months to replenish stores. 1
• Do not continue oral iron indefinitely without response—reassess after 4 weeks and switch to IV iron if hemoglobin fails to rise. 1
• Do not overlook vitamin C supplementation when oral iron response is suboptimal. 1
• Do not fail to identify and treat the underlying cause of iron deficiency while supplementing. 1, 6
• Do not use parenteral iron as first-line unless specific contraindications to oral therapy exist. 1

Failure to Respond

If anemia does not resolve within 6 months despite appropriate iron therapy:

• Reassess for ongoing blood loss 1
• Evaluate for malabsorption syndromes 1, 6
• Consider further gastrointestinal investigation 1
• Verify patient adherence to therapy 1
• Consider hematology consultation for complex cases 1