How do I interpret my iron status?

Interpreting Iron Status

Iron status should be assessed using a combination of serum ferritin and transferrin saturation (TSAT), with different interpretive thresholds depending on the presence or absence of inflammation. 1

Key Iron Status Parameters

Primary Markers

• Serum Ferritin: Reflects iron stores

  • Normal ranges: 20-250 μg/L in men, 20-200 μg/L in women 2
  • <30 μg/L indicates iron deficiency in non-inflammatory conditions 1
  • <100 μg/L may indicate iron deficiency in inflammatory conditions 1, 2

• Transferrin Saturation (TSAT):

  • Calculated as: (serum iron/total iron binding capacity) × 100%
  • Normal range: 20-50% 2
  • <20% suggests iron deficiency 2, 1
  • <16% with ferritin >100 μg/L suggests anemia of chronic disease 2

Supporting Markers

• Complete Blood Count (CBC):

  • Hemoglobin and hematocrit levels
  • Mean corpuscular volume (MCV): Low in iron deficiency
  • Red cell distribution width (RDW): Elevated in iron deficiency 1

• C-Reactive Protein (CRP):

  • Essential to assess inflammatory status when interpreting ferritin 2, 1

Interpretation Algorithm

1. Check for inflammation first (elevated CRP, clinical signs of inflammation)

   • If inflammation present: Use higher ferritin threshold (up to 100 μg/L) 2, 1
   • If no inflammation: Use standard ferritin threshold (<30 μg/L) 1

2. Interpret iron status based on combined markers:

   • Absolute iron deficiency:

     • Without inflammation: Ferritin <30 μg/L 1
     • With inflammation: Ferritin <100 μg/L 2, 1

   • Functional iron deficiency:

     • TSAT <20% with normal or elevated ferritin 2, 1
     • Common in chronic conditions or with erythropoietin therapy 1

   • Anemia of chronic disease:

     • Ferritin >100 μg/L and TSAT <16% with inflammation 2

   • Mixed deficiency (iron deficiency + chronic disease):

     • Ferritin 30-100 μg/L with inflammation 2

   • Normal iron status:

     • Ferritin and TSAT within normal ranges
     • No inflammation

Special Considerations

• Chronic Kidney Disease: Functional iron deficiency is common despite normal ferritin levels 2, 1

  • Higher ferritin thresholds (up to 100 μg/L) should be used 2
  • TSAT <20% suggests iron deficiency even with normal ferritin 2

• Inflammatory Bowel Disease/Chronic Inflammation:

  • Ferritin acts as an acute phase reactant and may be falsely elevated 2
  • Consider TSAT as more reliable in inflammatory states 2

• Advanced Testing (when available):

  • Reticulocyte hemoglobin content (CHr): <30 pg suggests iron-restricted erythropoiesis 1
  • Soluble transferrin receptor (sTfR): Elevated in iron deficiency, not affected by inflammation 2
  • Percent hypochromic red blood cells: >10% suggests iron deficiency 2

Common Pitfalls

• Relying solely on ferritin: Can be misleading in inflammatory states 2
• Ignoring inflammatory status: Critical for proper interpretation 2, 1
• Using single markers: Multiple parameters provide more accurate assessment 2
• Overlooking functional iron deficiency: Can occur despite normal ferritin levels 2, 1

Remember that accurate interpretation of iron status requires consideration of both iron markers and inflammatory status, as inflammation significantly affects the thresholds for diagnosis of iron deficiency.