Treatment of Iron Deficiency Anemia
Start ferrous sulfate 200 mg (65 mg elemental iron) once daily immediately—this is the preferred first-line treatment due to superior effectiveness, lowest cost, and equivalent tolerability compared to all other oral iron formulations. 1
First-Line Oral Iron Therapy
Ferrous sulfate 200 mg once daily is the only recommended formulation because it contains 65 mg of elemental iron per dose 2, costs significantly less than alternatives, and has no therapeutic disadvantage compared to other oral preparations 1
Once-daily dosing is superior to multiple daily doses because hepcidin levels remain elevated for 48 hours after iron intake, blocking further absorption and increasing gastrointestinal side effects without improving efficacy 1
Take on an empty stomach for optimal absorption, though taking with food is acceptable if gastrointestinal side effects occur 1
Add vitamin C (ascorbic acid) 500 mg with each iron dose to enhance absorption, particularly critical when transferrin saturation is severely low 1
Avoid tea and coffee within 1 hour of taking iron as these inhibit absorption 1
Alternative Oral Formulations (Only If Ferrous Sulfate Not Tolerated)
Ferrous gluconate contains only 38 mg elemental iron per 324 mg tablet 3, requiring higher pill burden with no proven tolerability advantage over ferrous sulfate 1
Ferrous fumarate is equally effective but typically more expensive 1
Do not use ferrous gluconate as first-line therapy—it is inferior due to lower elemental iron content and lack of evidence supporting better tolerability 1
Expected Response and Monitoring
Check hemoglobin at 4 weeks, expecting a rise of approximately 2 g/dL 1
Continue oral iron for 3 months after hemoglobin normalizes to fully replenish iron stores (total treatment duration typically 6-7 months) 1
Monitor hemoglobin and red cell indices every 3 months for the first year, then again after another year 1
When to Switch to Intravenous Iron
Switch to IV iron if any of the following conditions are met:
Intolerance to at least two different oral iron preparations (ferrous sulfate and one alternative) 1
Ferritin levels fail to improve after 4 weeks of compliant oral therapy 1
Active inflammatory bowel disease with hemoglobin <10 g/dL (use IV iron as first-line, not oral) 1
Post-bariatric surgery patients due to disrupted duodenal absorption 1
Celiac disease with inadequate response to oral iron despite strict gluten-free diet adherence 1
Ongoing gastrointestinal blood loss exceeding oral replacement capacity 1
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%) 1
Preferred IV Iron Formulations
Choose IV iron preparations that replace iron deficits in 1-2 infusions rather than multiple infusions to minimize risk 1
Ferric carboxymaltose (500-1000 mg single doses delivered within 15 minutes) is preferred 1
All IV iron formulations have similar overall safety profiles; true anaphylaxis is very rare (0.6-0.7%) 1
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 prescribe ferrous gluconate as first-line therapy—it contains less elemental iron (38 mg vs 65 mg) with no proven tolerability advantage 1, 3
Do not continue oral iron in patients with active inflammatory bowel disease and hemoglobin <10 g/dL—inflammation-induced hepcidin elevation severely impairs oral iron absorption, making IV iron first-line 1
Do not fail to add vitamin C supplementation—this significantly enhances absorption, especially with low transferrin saturation 1
Do not delay treatment while awaiting diagnostic workup unless colonoscopy is scheduled within days (iron interferes with visualization) 1
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 1
- Refer for further evaluation if hemoglobin <9.0 g/dL 1
Inflammatory Bowel Disease
- Use IV iron as first-line when hemoglobin <10 g/dL with active inflammation—oral iron is poorly absorbed and potentially harmful 1
- Treat active inflammation first to enhance iron absorption 1
- For mild anemia (hemoglobin >10 g/dL) with clinically inactive disease, oral iron may be appropriate 1
Post-Bariatric Surgery
- IV iron is preferred due to disrupted duodenal absorption mechanisms 1