Management of Low Serum Iron with Normal Ferritin in the Context of Inflammation
This patient has anemia of chronic disease (ACD), not iron deficiency, and the primary management should focus on identifying and treating the underlying inflammatory condition rather than iron supplementation. 1
Interpretation of Laboratory Findings
Your patient's iron studies demonstrate a classic pattern of anemia of chronic disease:
- Low serum iron (8 μmol/L) and low transferrin saturation (11%) indicate iron-restricted erythropoiesis 1
- Normal ferritin (172 μg/L) indicates adequate iron stores 1
- Normal hemoglobin (149 g/L) means the patient is not currently anemic 1
**The diagnostic criteria for ACD in the presence of inflammation are ferritin >100 μg/L and transferrin saturation <20%, which this patient meets.** 1 The ferritin level of 172 μg/L excludes true iron deficiency, as ferritin >100 μg/L is inconsistent with depleted iron stores even in inflammatory states. 1
Primary Management Strategy
1. Identify the Underlying Inflammatory Condition
The most critical step is investigating the source of inflammation or chronic disease causing the abnormal iron studies. 1 Look specifically for:
- Chronic infections (check for fever, night sweats, weight loss, chronic cough) 2, 3
- Inflammatory conditions including inflammatory bowel disease, rheumatologic disorders (measure CRP, ESR if not already done) 1
- Malignancy (age-appropriate cancer screening, unexplained weight loss, lymphadenopathy) 2, 3
- Chronic kidney disease (check creatinine, eGFR) 1
- Autoimmune diseases (joint symptoms, rashes, organ-specific symptoms) 2
2. Iron Supplementation is NOT Indicated
Iron supplementation should NOT be given to this patient at present. 1 Here's why:
- Ferritin >100 μg/L indicates adequate iron stores even in the presence of inflammation 1
- Iron supplementation will not correct ACD because the problem is not iron availability but rather inflammatory cytokine-mediated hepcidin elevation that blocks iron release from stores 3, 4
- Giving iron when stores are adequate is inefficient, has side effects, and may be harmful 5, 6
- The hemoglobin is currently normal, so there is no anemia requiring treatment 1
3. Monitoring Strategy
Repeat complete blood count, iron studies, and inflammatory markers (CRP) in 8-12 weeks or sooner if symptoms develop. 1, 5 Specifically monitor for:
- Development of anemia (hemoglobin <115 g/L for women) 1
- Changes in ferritin levels: If ferritin drops to 30-100 μg/L, this suggests evolving combined iron deficiency and ACD 1
- Persistent low transferrin saturation with declining ferritin would indicate true iron deficiency developing 1
Important Clinical Pitfalls
Common mistake: Treating low serum iron without considering ferritin and clinical context. 1 Low serum iron alone does not indicate iron deficiency—ferritin is the key discriminator in the absence of severe inflammation. 1
Ferritin between 30-100 μg/L represents a gray zone where combined iron deficiency and ACD likely coexist, and iron supplementation may be beneficial. 1 However, at 172 μg/L, this patient is well above that threshold.
If inflammation persists and anemia develops despite normal iron stores, consider erythropoiesis-stimulating agents rather than iron. 1, 4 Recombinant erythropoietin can correct ACD but cannot correct true iron deficiency, which helps distinguish these conditions. 4
When to Reconsider Iron Therapy
Iron supplementation would become appropriate if: 1
- Ferritin drops below 100 μg/L (suggesting evolving iron deficiency)
- Ferritin falls to 30-100 μg/L with transferrin saturation <16-20% (combined deficiency)
- Anemia develops (hemoglobin <115 g/L) with ferritin <100 μg/L
- The underlying inflammatory condition is treated and ferritin subsequently drops below thresholds
In inflammatory conditions, intravenous iron is preferred over oral iron if supplementation becomes necessary, as oral absorption is impaired by hepcidin elevation. 1, 6