What is the best iron regimen for elderly patients with iron deficiency anemia?

Best Iron Regimen for the Elderly

Start with ferrous sulfate 100-200 mg elemental iron once daily (or every other day if not tolerated), taken with vitamin C on an empty stomach, and switch to intravenous iron if there is no response after 4 weeks or if oral iron is not tolerated. 1

Initial Oral Iron Therapy

First-Line Formulation and Dosing

• Prescribe ferrous sulfate as the preferred formulation because it is the least expensive and no single oral iron formulation has demonstrated superiority over others 1
• Start with one tablet daily containing 100-200 mg elemental iron (ferrous sulfate, fumarate, or gluconate are all acceptable) 1
• Never dose more than once daily—increased dosing frequency elevates hepcidin levels for up to 48 hours, which paradoxically blocks further iron absorption while increasing side effects 1

Optimizing Absorption

• Add vitamin C supplementation (at least 80 mg, up to 500 mg) with each iron dose to enhance absorption by forming iron chelates and reducing ferric to ferrous iron 1, 2
• Take iron on an empty stomach in the morning when hepcidin levels are lowest for optimal absorption 1, 2
• If gastrointestinal side effects are intolerable, taking iron with food is acceptable despite reduced absorption—this trade-off may be necessary for adherence 1, 2
• Avoid tea and coffee within one hour of iron administration as they are powerful inhibitors of iron absorption 1, 2

Alternative Dosing for Poor Tolerance

• Consider every-other-day dosing if daily dosing causes intolerable side effects, as this schedule achieves similar iron absorption with better tolerability 1, 3
• Reduce to one tablet every other day before abandoning oral therapy entirely 1

Monitoring and Duration

Early Assessment

• Monitor hemoglobin response within the first 4 weeks of starting oral iron therapy 1, 3
• Check ferritin levels after 4 weeks—if ferritin fails to improve despite optimized oral therapy, proceed directly to intravenous iron 3

Treatment Duration

• Continue oral iron for approximately 3 months after hemoglobin normalization to adequately replenish marrow iron stores 1, 3
• Do not defer iron replacement while awaiting diagnostic investigations unless colonoscopy is imminent 1, 3

Indications for Intravenous Iron

When to Switch from Oral to IV

Switch to intravenous iron in the following situations:

• Patient cannot tolerate oral iron despite dosing adjustments 1, 3
• Ferritin levels fail to improve after 4 weeks of optimized oral therapy 3
• Conditions causing malabsorption are present (active inflammatory bowel disease, post-bariatric surgery, celiac disease) 1, 3
• Ongoing blood loss exceeds oral iron replacement capacity 3
• Rapid correction of anemia is required 4

IV Iron Administration

• Select high-dose IV formulations that replace iron deficits with 1-2 infusions rather than multiple infusions, such as ferric carboxymaltose or ferric derisomaltose at 500-1000 mg per infusion 1, 3
• For patients weighing ≥50 kg, administer ferric carboxymaltose 750 mg intravenously in two doses separated by at least 7 days for a total cumulative dose of 1,500 mg per course 5
• Monitor serum phosphate levels in patients requiring repeat IV iron courses, as ferric carboxymaltose carries increased risk for hypophosphatemia 1, 5, 4
• Observe patients for at least 30 minutes after IV iron administration for hypersensitivity reactions, though true anaphylaxis is very rare 1, 5

Special Considerations for the Elderly

Multifactorial Etiology

• Iron deficiency in the elderly is often multifactorial, requiring investigation for gastrointestinal blood loss, malabsorption, and inadequate dietary intake 1
• Carefully weigh risks and benefits of invasive endoscopic investigations in elderly patients with major comorbidities or limited performance status 1

Lower Dose Evidence

• A randomized trial in octogenarians demonstrated that 15 mg elemental iron daily was as effective as 150 mg daily for resolving iron deficiency anemia over 60 days, with significantly fewer adverse effects at the lower dose 6
• However, current guidelines prioritize 100-200 mg daily based on broader evidence, with dose reduction reserved for intolerance 1

Long-Term Management

• Consider long-term maintenance iron therapy if the underlying cause of iron deficiency is unknown or irreversible 1, 3
• Iron replacement therapy may be repeated if iron deficiency anemia recurs 5

Critical Pitfalls to Avoid

• Do not continue ineffective oral iron indefinitely—reassess after 4 weeks and switch to IV iron if no improvement 1, 3
• Do not prescribe iron more than once daily—this increases side effects without improving absorption 1
• Avoid excessive vitamin C supplementation (>500 mg daily) in patients with hemochromatosis or iron overload, as this can accelerate iron deposition and worsen cardiac function 3, 2
• Do not assume all oral iron failures are due to non-compliance—malabsorption and inflammation are common causes requiring IV therapy 3