How should I evaluate and manage a reproductive‑age woman with prolonged heavy menstrual bleeding and mild iron‑deficiency anemia (hemoglobin 110 g/L, low MCV (mean corpuscular volume), low MCH (mean corpuscular hemoglobin), low MCHC (mean corpuscular hemoglobin concentration))?

Management of Iron‑Deficiency Anemia in a Reproductive‑Age Woman with Prolonged Heavy Menstrual Bleeding

Begin oral ferrous sulfate 200 mg once daily with vitamin C 500 mg immediately, continue for 3 months after hemoglobin normalizes, and simultaneously evaluate menstrual blood loss and screen for celiac disease before considering gastrointestinal endoscopy.

Immediate Treatment Protocol

• Start ferrous sulfate 200 mg (65 mg elemental iron) once daily on an empty stomach without waiting for further diagnostic work‑up. 1
• Co‑administer vitamin C 500 mg with each iron dose to markedly enhance absorption, especially critical when transferrin saturation is low. 2, 1
• Once‑daily dosing is superior to multiple daily doses because hepcidin remains elevated for ~48 hours after each dose, blocking additional absorption and increasing gastrointestinal side effects without improving efficacy. 2, 1
• If ferrous sulfate is not tolerated, switch to ferrous fumarate (106 mg elemental iron) or ferrous gluconate (38 mg elemental iron), which provide comparable efficacy. 2, 1

Expected Response and Monitoring

• Hemoglobin should rise by approximately 2 g/dL after 3–4 weeks of treatment; a rise of ≥10 g/L within 2 weeks confirms iron deficiency even when initial iron studies are equivocal. 2, 1
• Continue oral iron for an additional 3 months after hemoglobin normalizes to fully replenish iron stores, resulting in a total treatment duration of 6–7 months. 2, 1
• Monitor hemoglobin and red‑cell indices every 3 months during the first year, then again after another year. 2, 1

Investigation of Underlying Cause in Premenopausal Women

• Assess menstrual blood loss first using pictorial blood loss assessment charts, which have 80% sensitivity and specificity for detecting menorrhagia; menstrual loss, pregnancy, and breastfeeding account for iron deficiency in 5–10% of menstruating women. 3, 1
• Screen for celiac disease with antiendomysial antibody and IgA measurement (to exclude IgA deficiency which makes the test unreliable), as celiac disease is present in 2–3% of iron‑deficiency anemia cases and can cause treatment failure if missed. 3, 2, 1
• In women under 45 years without upper gastrointestinal symptoms, endoscopy is not indicated; only patients with upper GI symptoms should have endoscopy and small bowel biopsy. 3
• Colonic investigation in patients less than 45 years should only be performed if there are specific indications such as rectal bleeding, family history of colon cancer, or alarm symptoms. 3, 1

When to Switch to Intravenous Iron

• Switch to IV iron if the patient cannot tolerate at least two different oral iron preparations (ferrous sulfate, fumarate, or gluconate). 2, 1
• Consider IV iron if ferritin levels fail to improve after 4 weeks of compliant oral therapy, or if hemoglobin does not rise by ≥1 g/dL after 4 weeks. 2, 1
• Prefer IV iron formulations that can replace iron deficits in 1–2 infusions, such as ferric carboxymaltose (750–1000 mg per 15‑minute infusion) or ferric derisomaltose (1000 mg as a single infusion). 2, 1
• Avoid iron dextran as first‑line IV therapy because it carries a higher risk of anaphylaxis (0.6–0.7%); most infusion reactions are complement‑activation pseudo‑allergies that respond to slowing the infusion rate. 2, 1

Critical Pitfalls to Avoid

• Do not prescribe multiple daily doses of oral iron, as this increases side effects without improving efficacy due to hepcidin‑mediated absorption blockade. 2, 1
• Do not stop iron therapy when hemoglobin normalizes; continue for an additional 3 months to replenish stores. 2, 1
• Do not overlook vitamin C supplementation when oral iron response is suboptimal, as ascorbic acid enhances iron absorption. 3, 2, 1
• Do not attribute iron deficiency solely to menstrual loss without screening for celiac disease, as its 2–3% prevalence in iron‑deficiency cases can lead to treatment failure. 3, 2, 1
• Do not pursue gastrointestinal endoscopy in women under 45 years without upper GI symptoms or alarm features, as menstrual loss is the most likely cause. 3, 1

Failure‑to‑Respond Algorithm

• If hemoglobin fails to rise by ≥2 g/dL after 4 weeks, verify adherence to oral iron therapy. 2, 1
• Evaluate for continued menstrual blood loss and consider gynecologic intervention for menorrhagia. 3, 4
• Reassess for malabsorption syndromes, particularly celiac disease, with antiendomysial antibody testing. 3, 2, 1
• If anemia does not resolve within 6 months despite appropriate iron therapy and menstrual management, consider further gastrointestinal investigation. 3, 2, 1