Iron Deficiency with Elevated Ferritin: Functional Iron Deficiency
Your laboratory results indicate functional iron deficiency (also called iron-restricted erythropoiesis), where despite adequate iron stores (ferritin 135 ng/mL), insufficient iron is available for red blood cell production, as evidenced by your low serum iron (20), high iron binding capacity (214), and critically low transferrin saturation (9%). 1
Understanding Your Results
Your laboratory pattern is characteristic of functional iron deficiency rather than absolute iron deficiency:
- Transferrin saturation of 9% is severely low (normal >20%), indicating inadequate iron delivery to bone marrow for red blood cell production 1
- Ferritin of 135 ng/mL suggests iron stores are present but not being mobilized effectively 1
- High TIBC (214) reflects your body's attempt to capture more circulating iron 1
This pattern commonly occurs with inflammatory conditions, chronic diseases, or conditions blocking iron release from stores (elevated hepcidin), even though storage iron exists 1.
Diagnostic Evaluation Required
Before initiating treatment, you must identify the underlying cause:
- Rule out inflammatory/chronic conditions: Check C-reactive protein (CRP) to identify inflammation that elevates ferritin falsely and blocks iron utilization 1, 2
- Evaluate for chronic diseases: Chronic kidney disease, heart failure, inflammatory bowel disease, and malignancy commonly cause this pattern 1, 3
- Assess for ongoing blood loss: Gastrointestinal evaluation (endoscopy if indicated), menstrual history in premenopausal women, and urinalysis to exclude hematuria 1
- Review medications: NSAIDs, anticoagulants, and proton pump inhibitors can contribute 1, 3
Treatment Approach
Initial Therapy
Oral iron supplementation should be attempted first unless contraindications exist:
- Ferrous sulfate 325 mg (65 mg elemental iron) daily or every other day is the first-line, most cost-effective option 1, 4, 3
- Alternative ferrous salts (gluconate, fumarate) are equally effective if sulfate is not tolerated 1
- Take on empty stomach when possible, or with meals if gastrointestinal side effects occur 1
- Add vitamin C 500 mg with iron to enhance absorption 1
- Continue for 3 months after hemoglobin normalizes to replenish iron stores 1
When to Use Intravenous Iron
Intravenous iron is indicated when:
- Active inflammation is present (elevated CRP) blocking oral iron absorption 1
- Chronic inflammatory conditions exist: IBD, CKD, heart failure, or active malignancy 1, 3
- Oral iron fails or is not tolerated after adequate trial 1, 3
- Ongoing significant blood loss exceeds oral replacement capacity 1
- Malabsorption conditions: Celiac disease, post-bariatric surgery, atrophic gastritis 1, 3
Multiple IV formulations exist (iron sucrose, ferric carboxymaltose, low-molecular-weight iron dextran, ferric gluconate), with ferric carboxymaltose allowing rapid administration of large single doses 1.
Monitoring and Follow-Up
- Recheck complete blood count, iron studies, and ferritin at 8-10 weeks after starting treatment 1, 2
- Do not recheck ferritin immediately after IV iron as levels will be falsely elevated 1
- Target transferrin saturation >20% and ferritin 100-500 ng/mL for optimal erythropoiesis 1
- Avoid chronic iron supplementation if ferritin normalizes without ongoing losses, as excess iron is potentially harmful 1, 2, 3
Critical Pitfalls to Avoid
- Do not dismiss treatment needs based solely on "normal" ferritin - your 9% transferrin saturation indicates severe functional deficiency requiring treatment 1
- Do not continue iron supplementation indefinitely without monitoring - iron overload risk exists when TSAT exceeds 50% or ferritin exceeds 500-800 ng/mL 1
- Do not use faecal occult blood testing for diagnosis - it is insensitive and non-specific 1
- Distinguish functional iron deficiency from inflammatory block - if no response to 8-10 doses of IV iron (50-125 mg weekly), suspect inflammatory block and address underlying inflammation first 1