At what ferritin level should iron supplements be started?

Iron Supplementation Thresholds Based on Ferritin Levels

Iron supplementation should be initiated when serum ferritin levels are below 30 μg/L in individuals without inflammatory conditions, or below 100 μg/L in patients with inflammation or chronic disease. 1

Diagnostic Criteria for Iron Deficiency

The diagnosis of iron deficiency depends on the presence or absence of inflammation:

• Without inflammation/chronic disease:

  • Serum ferritin < 30 μg/L
  • Transferrin saturation < 16%
  • High Total Iron-Binding Capacity (TIBC) 1

• With inflammation/chronic disease:

  • Serum ferritin < 100 μg/L
  • Transferrin saturation < 20% 2, 1
  • If ferritin is between 30-100 μg/L with inflammation, a combination of true iron deficiency and anemia of chronic disease is likely 2

Treatment Algorithm

1. For patients without inflammation or chronic disease:

   • Start oral iron when ferritin < 30 μg/L 1
   • Recommended dose: 60-200 mg elemental iron daily 1
   • Consider adding vitamin C 250-500 mg with iron to enhance absorption 1

2. For patients with inflammation or chronic disease (IBD, CKD, cancer, etc.):

   • Start iron supplementation when ferritin < 100 μg/L 2, 1
   • For mild anemia with clinically inactive disease: oral iron may be used 2
   • For clinically active disease: intravenous iron should be first-line 2

3. Special considerations for intravenous iron:

   • Indicated when ferritin < 100 μg/L with:
     • Clinically active inflammatory disease
     • Previous intolerance to oral iron
     • Hemoglobin < 100 g/L
     • Need for erythropoiesis-stimulating agents
     • Malabsorption
     • Ongoing blood loss 2, 1, 3

Monitoring and Treatment Goals

• Monitor hemoglobin and iron studies after 4 weeks of treatment 1
• Continue iron therapy for three months after correction of anemia 1
• Target parameters:
  • Serum ferritin > 100 ng/mL
  • Transferrin saturation > 20%
  • Hemoglobin 11-12 g/dL 1

Important Clinical Considerations

• Iron deficiency without anemia can cause significant symptoms including fatigue, irritability, depression, difficulty concentrating, and restless legs syndrome 3
• Long-term daily iron supplementation with normal/high ferritin values is potentially harmful and not recommended 1
• In chronic kidney disease patients, the 2012 KDIGO guidelines specified ferritin ≤ 500 ng/ml and transferrin saturation ≤ 30% as thresholds for iron parameters 4
• For heart failure patients with iron deficiency, intravenous iron has shown improvements in symptom status, with iron deficiency defined as ferritin < 100 ng/mL or ferritin 100-300 ng/mL when transferrin saturation < 20% 5

Common Pitfalls to Avoid

• Focusing solely on hemoglobin without checking iron parameters can miss non-anemic iron deficiency, which still causes significant symptoms 3, 6
• Interpreting borderline values as abnormal when the overall pattern indicates normal iron status can result in unnecessary interventions 1
• Failing to adjust ferritin thresholds in the presence of inflammation can lead to missed diagnoses 2, 1
• Unnecessary vitamin C supplementation with oral iron may not provide additional benefit for iron absorption in all patients 7

By following these evidence-based guidelines for initiating iron supplementation based on ferritin levels, clinicians can effectively manage iron deficiency and improve patient outcomes related to morbidity, mortality, and quality of life.