Treatment of Chronic Iron Deficiency Anemia
Start with oral ferrous sulfate 50-100 mg elemental iron once daily on an empty stomach as first-line therapy for most patients with chronic IDA, reserving intravenous iron for specific clinical scenarios including intolerance, malabsorption, ongoing blood loss exceeding absorption capacity, inflammatory conditions, or hemoglobin <10 g/dL in inflammatory bowel disease. 1
Initial Oral Iron Therapy
Prescribe ferrous sulfate 200 mg tablets (containing 65 mg elemental iron) once daily in the fasting state as the optimal starting regimen, balancing efficacy with tolerability while being the simplest and least expensive option 1, 2
Alternate-day dosing produces similar hemoglobin increments with significantly lower nausea rates, though with slower initial response, making it a reasonable alternative for patients experiencing gastrointestinal side effects 1
Lower daily doses (50 mg elemental iron) produce faster hemoglobin rise but achieve similar ultimate outcomes compared to higher doses (100-200 mg), supporting the use of lower therapeutic doses 1
Monitoring and Response Assessment
Check hemoglobin at 2 weeks: absence of at least 1.0 g/dL (10 g/L) rise predicts subsequent treatment failure with 90.1% sensitivity and 79.3% specificity, indicating the need to transition to intravenous iron 1, 3
Recheck hemoglobin every 4 weeks until normalized, with typical response showing improvement within 1 month of oral therapy 1
Continue oral iron for 2-3 months after hemoglobin normalization to replenish iron stores, as premature discontinuation leads to recurrence 1, 4
Intravenous Iron Therapy Indications
Switch to IV iron in the following specific scenarios:
Inflammatory bowel disease with hemoglobin <10 g/dL: IV iron is first-line therapy with odds ratio of 1.57 (95% CI 1.13-2.18) for achieving hemoglobin increase of 2.0 g/dL compared to oral iron 5, 1
Ongoing blood loss exceeding intestinal absorption capacity (e.g., heavy uterine bleeding, intestinal angiodysplasia) where oral iron cannot compensate for the rate of iron loss 1, 6
Malabsorption conditions including celiac disease, post-bariatric surgery patients, or inflammatory bowel disease with active inflammation 1
Oral iron intolerance with gastrointestinal side effects preventing adequate adherence 1, 7
Failed oral iron trial defined by <1.0 g/dL hemoglobin increase at 2 weeks 3
IV Iron Formulations and Administration
Ferric carboxymaltose, ferric derisomaltose, and iron sucrose are suitable options with different dosing regimens 1
Iron sucrose can be administered as 200 mg over 10 minutes, with multiple doses potentially required based on severity 6
IV iron produces clinically meaningful hemoglobin response within 1 week, significantly faster than oral therapy 1
Resuscitation facilities should be available during administration as a precaution for potential adverse reactions 6
Special Population Considerations
Inflammatory Bowel Disease:
- Oral iron may be appropriate only in carefully selected patients with mild anemia (hemoglobin >10 g/dL), clinically inactive disease, and demonstrated tolerance, requiring close follow-up 5, 1
- Address underlying inflammation first to control ulceration and chronic blood loss 1
Portal Hypertensive Gastropathy:
- Oral iron therapy is sufficient as there is no malabsorptive defect, though IV iron is reasonable in severe iron depletion 5
- Address underlying cirrhosis with nonselective β-blockers, transjugular intrahepatic portosystemic shunts, or liver transplantation 5
Post-Bariatric Surgery:
- IV iron is preferred in severe cases or when oral supplementation is ineffective 1
- Perform esophagogastroduodenoscopy to exclude anastomotic ulcer disease causing chronic bleeding 1
Celiac Disease:
- Most patients improve with strict gluten-free diet even without iron supplementation, but exclude other causes of iron deficiency 5
Blood Transfusion
Transfusion is rarely required and should be reserved for severe symptomatic anemia with circulatory compromise, targeting hemoglobin 70-90 g/L 1
Consider parenteral iron as an alternative before transfusion, as each unit of blood contains only ~200 mg elemental iron, insufficient to replenish stores in severe IDA 1
Common Pitfalls to Avoid
Do not continue oral iron beyond 2 weeks without documented hemoglobin response, as this delays appropriate transition to IV iron 3
Do not prescribe high-dose oral iron (>100 mg elemental iron daily) as lower doses are equally effective with better tolerability 1
Do not stop iron therapy when hemoglobin normalizes, as 2-3 additional months are required to replenish stores 1, 4
Do not use oral iron as first-line in IBD patients with hemoglobin <10 g/dL, as IV iron has superior efficacy and tolerability in this population 5, 1