What is the recommended treatment approach for correcting Iron Deficiency Anemia (IDA) in adults, including pregnant women?

Treatment of Iron Deficiency Anemia

Start oral ferrous sulfate 200 mg (65 mg elemental iron) once daily on an empty stomach, add vitamin C 500 mg with each dose, and continue for 3 months after hemoglobin normalizes—switching to intravenous iron only if oral therapy fails after 4 weeks with confirmed adherence, or in specific conditions where oral absorption is impaired. 1, 2, 3

First-Line Oral Iron Therapy

Ferrous sulfate is the preferred formulation because it contains the highest elemental iron content (65 mg per 200 mg tablet) and is consistently the least expensive option, with no therapeutic advantage of any other oral iron preparation over another. 3, 4

Dosing Strategy

• Prescribe once-daily dosing, never multiple times per day. Once-daily dosing improves tolerance while maintaining equal or better iron absorption compared to multiple daily doses because hepcidin levels remain elevated for 48 hours after iron intake, blocking further absorption. 2, 3, 5

• Take on an empty stomach for optimal absorption, though taking with food is acceptable if gastrointestinal side effects occur. 2, 3

• Add vitamin C (ascorbic acid) 500 mg with each iron dose to enhance absorption, especially critical when transferrin saturation is severely low. 2, 3

• Avoid tea, coffee, antacids, and proton pump inhibitors within 1 hour of taking iron, as these significantly decrease absorption. 2

• Alternative formulations (ferrous gluconate 38 mg elemental iron or ferrous fumarate 106 mg elemental iron per tablet) are equally effective if ferrous sulfate is not tolerated. 2, 3

Expected Response and Monitoring

• Check hemoglobin at 4 weeks, expecting a rise of approximately 2 g/dL. 1, 2, 3

• Continue oral iron for 3 months after hemoglobin normalizes to fully replenish iron stores—total treatment duration typically 6-7 months. 1, 2, 3

• Monitor hemoglobin and red cell indices every 3 months for the first year, then again after another year. 3

When to Switch to Intravenous Iron

Intravenous iron replaces oral therapy in specific clinical scenarios where oral iron is ineffective or contraindicated:

Absolute Indications for IV Iron

• Active inflammatory bowel disease with hemoglobin <10 g/dL—inflammation-induced hepcidin elevation severely impairs oral iron absorption, making IV iron first-line therapy. 1, 6, 3

• Intolerance to at least two different oral iron preparations despite trying ferrous sulfate, ferrous fumarate, and ferrous gluconate. 2, 3

• Failure of ferritin levels to improve after 4 weeks of compliant oral therapy with confirmed adherence and absence of acute illness. 2, 6, 3

• Post-bariatric surgery patients—disrupted duodenal absorption mechanisms make IV iron the preferred route. 6, 3

• Celiac disease with inadequate response to oral iron despite strict gluten-free diet adherence. 6, 3

• Ongoing gastrointestinal blood loss exceeding oral replacement capacity. 3

IV Iron Formulations

• Prefer formulations that replace iron deficits in 1-2 infusions rather than multiple infusions to minimize risk and improve convenience. 6, 3

• Ferric carboxymaltose (500-1000 mg single doses, 15-minute infusion) is the preferred agent based on clinical trial evidence, particularly in pregnancy and postpartum populations. 6, 3

• Iron dextran can be given as total dose infusion but carries a 0.6-0.7% risk of serious reactions including anaphylaxis, requiring resuscitation facilities available. 6

• Iron sucrose requires multiple visits with maximum 200 mg per dose over 10 minutes. 6

Special Population Considerations

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, 6

• Refer if hemoglobin <9.0 g/dL or Hct <27.0% to a physician familiar with anemia during pregnancy for further medical evaluation. 1, 6

• If no response after 4 weeks (hemoglobin does not increase by 1 g/dL or Hct by 3%) despite compliance, switch to intravenous iron therapy—ferric carboxymaltose 15 mg/kg up to 750 mg per dose, two occasions separated by at least 7 days. 1, 6

• In women of African, Mediterranean, or Southeast Asian ancestry, mild anemia unresponsive to iron therapy may be due to thalassemia minor or sickle cell trait—perform MCV, RDW, and serum ferritin. 1, 6

• When hemoglobin normalizes for gestational age, decrease to maintenance dose of 30 mg/day oral iron. 1, 6

Non-Pregnant Women and Men

• Treat with 60-120 mg/day elemental iron orally. 1, 2

• Follow up at 4 weeks—if no response despite compliance, further evaluate with MCV, RDW, and serum ferritin. 1, 2

• Continue iron treatment for 2-3 more months after anemia correction in adolescent girls and nonpregnant women. 1

Postpartum Women

• Screen at 4-6 weeks postpartum if risk factors present (anemia continued through third trimester, excessive blood loss during delivery, multiple birth). 1

• Treatment and follow-up are the same as for nonpregnant women. 1

• If no risk factors for anemia are present, stop supplemental iron at delivery. 1

Men and Postmenopausal Women

• No routine screening recommended. 1

• Iron deficiency or anemia detected during routine examinations should be fully evaluated for its cause—approximately one-third have underlying pathological abnormality, most commonly in the gastrointestinal tract. 1

• Men and postmenopausal women usually do not need iron supplements unless deficiency is confirmed. 1

Critical Pitfalls to Avoid

• Do not prescribe multiple daily doses—this increases side effects without improving efficacy due to hepcidin-mediated absorption blockade. 2, 3, 5

• Do not stop iron therapy when hemoglobin normalizes—continue for 3 months to replenish stores. 2, 3

• Do not overlook vitamin C supplementation when oral iron response is suboptimal, as this significantly enhances absorption. 2, 3

• Do not continue oral iron indefinitely without response—reassess after 4 weeks and switch to IV iron if hemoglobin fails to rise by 2 g/dL. 2, 3

• Do not prescribe oral iron to patients with active inflammatory bowel disease and hemoglobin <10 g/dL—this is ineffective and potentially harmful; use IV iron instead. 6, 3

• Do not assume adherence without verification—frequent side effects often lead to treatment discontinuation. 2

• Do not attribute iron deficiency anemia solely to aspirin or proton pump inhibitors without completing appropriate gastrointestinal investigations. 2

Investigation of Underlying Cause

While initiating iron replacement, simultaneously investigate the cause of iron deficiency:

• In premenopausal women, assess menstrual blood loss first—menorrhagia, pregnancy, and breastfeeding account for iron deficiency in 5-10% of menstruating women. 3

• Screen for celiac disease with antiendomysial antibody and IgA measurement, especially in younger patients. 3

• Gastrointestinal investigation with bidirectional endoscopy is indicated in men, postmenopausal women, and premenopausal women with alarm features or family history of colon cancer. 1, 3

• Do not delay iron replacement while awaiting investigations unless colonoscopy is scheduled within days, as iron can interfere with visualization. 3