How to manage a patient with iron deficiency anemia?

Management of Iron Deficiency Anemia

Laboratory Interpretation

Your patient has iron deficiency anemia with severely depleted iron stores despite a seemingly "normal" ferritin of 135 ng/mL. The iron saturation of 9% (critically low, normal >20%) and total iron of 20 μg/dL confirm true iron deficiency, while the elevated TIBC of 214 μg/dL indicates the body is desperately trying to capture any available iron 1. The ferritin level, though appearing adequate, can be falsely elevated by inflammation, infection, or chronic disease, masking underlying iron deficiency 2.

Immediate Treatment Protocol

Start ferrous sulfate 200 mg (65 mg elemental iron) once daily immediately—this is the gold standard first-line therapy. 3, 1, 2

• Take with 500 mg vitamin C (ascorbic acid) to enhance absorption, which is critical given your patient's severely low iron saturation of 9% 3, 1, 2
• Once-daily dosing is superior to multiple daily doses because hepcidin (the iron regulatory hormone) blocks further absorption after the first dose, making additional doses ineffective while increasing gastrointestinal side effects 2
• Take on an empty stomach for optimal absorption, but with food if gastrointestinal symptoms occur 2
• If ferrous sulfate is not tolerated, switch to ferrous fumarate or ferrous gluconate—all are equally effective 3, 1, 2

Expected Response and Monitoring

• Check hemoglobin at 4 weeks—expect a rise of approximately 2 g/dL 3, 1, 2
• Continue iron therapy for 3 months after hemoglobin normalizes to fully replenish iron stores 3, 1
• Monitor hemoglobin and red cell indices every 3 months for the first year, then once more after another year 3, 1

Investigate the Underlying Cause

You must identify why this patient is iron deficient—treatment without finding the source risks missing serious pathology. 3, 1

For Premenopausal Women:

• Assess menstrual blood loss first, as menorrhagia, pregnancy, and breastfeeding account for iron deficiency in 5-10% of menstruating women 3, 1
• Consider pictorial blood loss assessment charts (80% sensitivity/specificity for menorrhagia) 3
• Screen for celiac disease with antiendomysial antibody and IgA measurement—this is a common cause of malabsorption in younger patients 1, 2
• Gastrointestinal investigation is only needed if: upper GI symptoms present, family history of colorectal cancer, or persistent IDA after treating menorrhagia and supplementing iron 3, 1

For Men and Postmenopausal Women:

• Perform upper endoscopy and colonoscopy immediately—gastrointestinal blood loss (including colon cancer) is the most common cause 3, 1, 4
• Screen for celiac disease 1, 2

When to Switch to Intravenous Iron

Reserve IV iron for specific indications only—oral iron should work if the patient is compliant and absorbing properly. 3, 1, 2

Switch to IV iron if:

• Intolerance to at least two different oral iron preparations 3, 1, 2
• No hemoglobin rise after 4 weeks despite confirmed compliance 1, 2
• Active inflammatory bowel disease with hemoglobin <10 g/dL 1, 2
• Post-bariatric surgery (disrupted duodenal absorption) 1, 2
• Celiac disease with inadequate response despite gluten-free diet adherence 1, 2
• Ongoing gastrointestinal blood loss exceeding oral replacement capacity 2

Preferred IV formulations: Ferric carboxymaltose or ferric derisomaltose (500-1000 mg single doses, can replace deficit in 1-2 infusions) 1, 2, 5

Avoid iron dextran due to higher anaphylaxis risk 2

Failure to Respond After 4 Weeks

If hemoglobin fails to rise by 2 g/dL after 4 weeks, the causes are: 3, 1, 2

• Poor compliance (most common)
• Continued blood loss (reassess for occult bleeding)
• Malabsorption (celiac disease, inflammatory bowel disease, post-bariatric surgery)
• Misdiagnosis (anemia of chronic disease, thalassemia trait, combined deficiencies)

Critical Pitfalls to Avoid

• Never prescribe multiple daily doses (e.g., three times daily)—this increases side effects without improving efficacy due to hepcidin-mediated absorption blockade 1, 2
• Never stop iron when hemoglobin normalizes—continue for 3 months to replenish stores 3, 1
• Never overlook vitamin C supplementation when iron saturation is severely low 3, 1, 2
• Never fail to investigate the underlying cause, especially in patients >45 years or men of any age 3, 1
• Never use parenteral iron as first-line unless specific contraindications to oral therapy exist—it's painful, expensive, and carries anaphylaxis risk 3, 6
• Never assume ferritin alone rules out iron deficiency—ferritin up to 100 ng/mL can still indicate iron deficiency when inflammation is present 2

Special Considerations

• Avoid taking iron within 2 hours of tetracycline antibiotics (interferes with absorption of both) 6
• Black stools are expected and harmless 6
• If pregnant, refer for further evaluation if hemoglobin <9.0 g/dL 2
• In patients of African, Mediterranean, or Southeast Asian ancestry with anemia unresponsive to iron, consider thalassemia minor or sickle cell trait 2