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

Treatment for Iron Deficiency Anemia

First-Line Treatment: Oral Ferrous Sulfate

Start ferrous sulfate 200 mg (65 mg elemental iron) once daily on an empty stomach—this is the preferred first-line treatment due to superior effectiveness, low cost, and better tolerability compared to multiple daily dosing. 1, 2

• Ferrous sulfate 324 mg tablets contain 65 mg of elemental iron 3
• Take as a single morning dose rather than divided throughout the day 1, 2
• Once-daily dosing is superior because hepcidin (the iron absorption regulator) remains elevated for 48 hours after iron intake, blocking further absorption if multiple doses are given 1, 4
• If gastrointestinal side effects occur, taking with food is acceptable though absorption decreases 1
• Alternative formulations (ferrous gluconate or ferrous fumarate) are equally effective if ferrous sulfate is not tolerated 2, 5

Optimize Absorption

Add vitamin C (ascorbic acid) 500 mg with each iron dose to enhance absorption, particularly critical when transferrin saturation is low. 1, 2

• If daily dosing is not tolerated, switch to alternate-day dosing (every other day), which increases fractional iron absorption and improves tolerance with similar efficacy 1, 4
• Alternate-day dosing allows hepcidin levels to subside by 48 hours, maximizing the next dose's absorption 4

Expected Response and Treatment Duration

Hemoglobin should rise by approximately 2 g/dL after 3-4 weeks of treatment. 1, 2

• Check hemoglobin at 4 weeks to confirm response 1, 2
• If no rise occurs within 4 weeks, assess for non-adherence, ongoing blood loss, or malabsorption 1
• Continue oral iron for 3 months after hemoglobin normalizes to fully replenish iron stores—total treatment typically lasts 6-7 months 1, 2
• Monitor hemoglobin and red cell indices every 3 months for the first year, then again after another year 1, 2

When to Switch to Intravenous Iron

Use IV iron if the patient meets any of these criteria:

• Intolerance to at least two different oral iron preparations (ferrous sulfate, ferrous fumarate, and ferrous gluconate) 1, 2
• Failure of ferritin levels to improve after 4 weeks of compliant oral therapy 1, 2
• Active inflammatory bowel disease with hemoglobin <10 g/dL—inflammation-induced hepcidin elevation severely impairs oral iron absorption 1, 2
• Post-bariatric surgery patients due to disrupted duodenal absorption mechanisms 1, 2
• Celiac disease with inadequate response to oral iron despite strict gluten-free diet adherence 1, 2
• Ongoing gastrointestinal blood loss exceeding oral replacement capacity 6, 7
• Chronic kidney disease with functional iron deficiency (ferritin 100-300 ng/mL with transferrin saturation <20%) 2
• Chronic heart failure with iron deficiency (ferritin <100 ng/mL or 100-300 ng/mL with transferrin saturation <20%) 2

IV Iron Formulation Selection

• Prefer IV iron preparations that replace iron deficits in 1-2 infusions rather than multiple infusions 1, 2
• 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%) 2
• Most reactions are complement activation-related pseudo-allergy (infusion reactions) that respond to slowing the infusion rate 2

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 if hemoglobin <10 g/dL with clinically active IBD—oral iron is poorly absorbed and may worsen inflammation 1, 2
• Oral iron may be appropriate only for mild anemia (hemoglobin >10 g/dL) with clinically inactive disease 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 1
• Refer if hemoglobin <9.0 g/dL for further medical evaluation 1
• IV iron is indicated during second and third trimesters if oral iron fails 2

Celiac Disease

• Ensure strict adherence to gluten-free diet to improve iron absorption 1, 2
• Screen with antiendomysial antibody and IgA measurement 1, 7
• Progress to IV iron if oral supplementation fails despite dietary compliance 1, 2

Post-Bariatric Surgery

• IV iron is preferred due to disrupted duodenal absorption mechanisms 1, 2

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, 4
• Do not stop iron therapy when hemoglobin normalizes—continue for 3 months to replenish stores 1, 2
• Do not continue oral iron indefinitely without response—reassess after 4 weeks and switch to IV iron if hemoglobin fails to rise 1, 2
• 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 supplementing 1, 2, 7
• Do not delay iron supplementation while awaiting diagnostic workup unless colonoscopy is scheduled within days 2

Diagnostic Workup for Underlying Cause

• In premenopausal women, assess menstrual blood loss first—menorrhagia accounts for iron deficiency in 5-10% of menstruating women 1, 7
• Patients >45 years should undergo bidirectional endoscopy (upper endoscopy and colonoscopy) 1
• Patients <45 years should have endoscopy only if upper GI symptoms are present; otherwise perform celiac disease screening 1, 7
• If anemia does not resolve within 6 months despite appropriate therapy, consider small bowel evaluation and hematology consultation 1, 2