In an elderly patient with iron‑deficiency anemia, at what serum ferritin and transferrin saturation values should intravenous iron infusion be initiated?

Iron Infusion Thresholds for Elderly Patients with Iron Deficiency Anemia

In elderly patients with iron deficiency anemia, intravenous iron infusion should be initiated when ferritin is <100 ng/mL with transferrin saturation <20%, or when hemoglobin is <10 g/dL, particularly if oral iron has failed or is not tolerated. 1, 2

Diagnostic Thresholds for IV Iron

Ferritin and Transferrin Saturation Criteria

• Ferritin <30-45 ng/mL confirms absolute iron deficiency and warrants IV iron consideration 1, 2
• Ferritin 30-100 ng/mL with transferrin saturation <20% indicates functional iron deficiency requiring IV iron 3, 1
• In the presence of inflammation (common in elderly), ferritin up to 100 ng/mL may still represent iron deficiency 3, 1
• Transferrin saturation <15-20% confirms depleted iron stores regardless of ferritin level 3, 1

Hemoglobin-Based Criteria

• Hemoglobin <10 g/dL is a clear indication for IV iron as first-line therapy 3
• For hemoglobin 10-12 g/dL in women or 10-13 g/dL in men, IV iron should be considered if oral iron fails or is not tolerated 1, 2

Clinical Situations Favoring IV Iron Over Oral

IV iron should be first-line treatment in elderly patients when: 3

• Previous intolerance to oral iron (gastrointestinal side effects occur in ~50% of patients) 2
• Active inflammatory conditions or chronic disease 3
• Need for rapid correction of anemia 3
• Hemoglobin <10 g/dL 3
• Malabsorption suspected 2

Dosing Based on Body Weight and Hemoglobin

For patients ≥50 kg: 4

• Standard dose: 750 mg IV iron in two doses separated by ≥7 days (total 1,500 mg per course) 4
• Alternative: Single dose of 15 mg/kg up to maximum 1,000 mg 4

For patients <50 kg: 4

• 15 mg/kg IV in two doses separated by ≥7 days 4

Weight and hemoglobin-based dosing (from IBD guidelines, applicable to elderly): 3

• Body weight <70 kg with Hb 10-12 g/dL: 1,000 mg total iron 3
• Body weight ≥70 kg with Hb 10-12 g/dL: 1,500 mg total iron 3
• Body weight <70 kg with Hb 7-10 g/dL: 1,500 mg total iron 3
• Body weight ≥70 kg with Hb 7-10 g/dL: 2,000 mg total iron 3

Important Caveats for Elderly Patients

Upper Safety Limits

• Do not exceed transferrin saturation >50% or ferritin >800 ng/mL to avoid iron overload 3
• Monitor serum phosphate levels in elderly requiring repeat courses, especially if within 3 months 4

When Oral Iron May Be Acceptable

Oral iron (100 mg elemental iron daily maximum) can be considered only if: 3, 1

• Hemoglobin 11-12 g/dL (mild anemia) 3
• No active inflammatory disease 3
• No previous intolerance to oral iron 3
• Patient can tolerate and absorb oral preparations 2

Response Monitoring

• Reassess hemoglobin and iron studies in 2-4 weeks after initiating treatment 1, 5
• Expected response: 1-2 g/dL hemoglobin increase within 4 weeks 1, 5
• If no response after 4 weeks of oral iron, switch to IV iron 1, 5

Maintenance Therapy

• Re-treat when ferritin drops below 100 ng/mL or hemoglobin falls below 12 g/dL (women) or 13 g/dL (men) 3, 1
• Target ferritin >100 ng/mL to prevent rapid recurrence 3, 1

Safety Considerations Specific to Elderly

• Monitor for hypersensitivity reactions for at least 30 minutes post-infusion 4
• Serious anaphylactic reactions occur in only 0.1% of patients with modern formulations 4, 2
• Avoid extravasation as brown discoloration may be long-lasting 4
• IV iron is generally safer and better tolerated than oral iron in elderly (2.7% vs 26.2% adverse events) 6