Switch to Intravenous Iron Immediately
This patient has failed oral iron supplementation and requires intravenous iron therapy. Despite being on oral iron, her ferritin remains severely depleted at 7 ng/mL (normal 16-232), transferrin saturation is only 12% (normal 16-45%), and she has persistent microcytic anemia (MCV 80.3 fL, MCH 24.7 pg, MCHC 30.7 g/dL—all low). 1
Why Oral Iron Has Failed
Inadequate response to oral therapy: After a trial of oral iron, ferritin should increase and anemia should improve. This patient's ferritin of 7 ng/mL indicates oral iron is either not being absorbed, not being taken properly, or losses exceed replacement. 1, 2
Persistent severe iron depletion: Ferritin <15 ng/mL represents absent iron stores, and her transferrin saturation of 12% confirms functional iron deficiency affecting erythropoiesis. 1, 3
Microcytic indices confirm ongoing iron-restricted erythropoiesis: The low MCV (80.3), MCH (24.7), and MCHC (30.7) with elevated RDW (16.0%) demonstrate that despite oral supplementation, her bone marrow cannot access sufficient iron for normal red cell production. 1, 3
Recommended Treatment Algorithm
Immediate Action: Intravenous Iron
First-line IV options (choose based on availability and convenience): 1, 2
- Ferric carboxymaltose (Ferinject): 1000 mg over 15 minutes—preferred for single-dose convenience 1
- Iron sucrose (Venofer): 200 mg over 10 minutes, may require multiple doses 1, 2
- Iron dextran (Cosmofer): 20 mg/kg over 6 hours—avoid due to higher anaphylaxis risk (0.6-0.7%) 1, 2
Dosing Strategy
Calculate total iron deficit: For a 47-year-old woman with Hb 12.9 g/dL and depleted stores, approximately 1000-1500 mg total elemental iron is needed. 1, 4
Preferred approach: Single infusion of ferric carboxymaltose 1000 mg, which can replace iron deficits efficiently and has excellent safety profile. 1
Monitoring Response
Recheck labs in 8-10 weeks (not earlier—ferritin will be falsely elevated immediately post-infusion): 1, 2
- Hemoglobin should increase by approximately 2 g/dL
- Ferritin target: 100-200 ng/mL (avoid exceeding 500 ng/mL)
- Transferrin saturation should normalize to >20%
- MCV, MCH, MCHC should normalize
Long-term monitoring: Check CBC and iron indices every 3 months for the first year, then annually. 1, 2
Critical Next Steps Beyond Iron Replacement
Investigate Why Oral Iron Failed
Must evaluate for underlying causes: 1, 3
Gastrointestinal blood loss: At age 47, she requires bidirectional endoscopy (upper endoscopy and colonoscopy) to exclude occult GI bleeding, even if asymptomatic. 1, 3
Malabsorption disorders: Test for celiac disease with tissue transglutaminase antibodies (tTG), as celiac disease affects up to 4% of women with iron deficiency anemia. 1, 2
Menstrual losses: Assess for menorrhagia if premenopausal—may require gynecologic evaluation. 1, 3
Medication interference: Review for proton pump inhibitors, H2 blockers, or antacids that impair iron absorption. 3, 5
If Underlying Cause Requires Ongoing Oral Iron
Only after IV repletion and if absorption pathway is intact: 2, 6
Consider adding vitamin C 250-500 mg twice daily with oral iron to enhance absorption (though evidence is limited). 1, 2
Alternative: Alternate-day dosing (e.g., 100-200 mg elemental iron every other day) may improve absorption and reduce GI side effects compared to daily dosing. 1, 5
Common Pitfalls to Avoid
Do not continue oral iron alone—this patient has already demonstrated failure of oral therapy. 1, 2
Do not delay IV iron while pursuing diagnostic workup—treat the deficiency while investigating the cause. 1, 2
Do not recheck ferritin immediately after IV iron—wait 8-10 weeks as levels will be falsely elevated. 1, 2
Do not assume compliance is the only issue—true malabsorption (celiac disease, inflammatory bowel disease, H. pylori gastritis, atrophic gastritis) or ongoing blood loss must be excluded. 1, 3
Ensure resuscitation facilities are available during IV iron administration for rare hypersensitivity reactions, though true anaphylaxis is very rare with modern formulations. 1, 2