What are the normal reference ranges for iron studies (serum iron, ferritin, total iron‑binding capacity, transferrin saturation) and related CBC parameters (hemoglobin, mean corpuscular volume) in a healthy adult that support normal hair growth?

Normal Iron Profile Reference Ranges for Healthy Hair Growth

For optimal hair health, maintain serum ferritin ≥30 ng/mL, transferrin saturation 20-50%, hemoglobin ≥12 g/dL in women and ≥13 g/dL in men, with normal MCV 80-100 fL and TIBC 250-370 mg/dL. 1, 2

Complete Iron Panel Reference Ranges

Core Iron Studies

• Serum Iron: 50-175 µg/dL in healthy adults 1

  • This measures circulating iron bound to transferrin
  • Subject to significant day-to-day and diurnal variation 1, 3

• Total Iron-Binding Capacity (TIBC): 250-370 µg/dL (45-66 µmol/L) 1

  • Reflects the availability of iron-binding sites on transferrin
  • Increases when iron stores are depleted 1, 4

• Transferrin Saturation (TSAT): 20-50% 1

  • Calculated as: (Serum Iron ÷ TIBC) × 100 4
  • Values <16% indicate iron deficiency 4
  • Values <20% confirm absolute iron deficiency 4

• Serum Ferritin:

  • Men: 20-250 µg/L (or 24-336 µg/L depending on assay) 1
  • Women: 20-200 µg/L 1
  • Critical threshold for hair health: ≥30 ng/mL 2

Complete Blood Count Parameters

• Hemoglobin:

  • Men: 13.5-17.5 g/dL 1
  • Women: 12.0-15.5 g/dL 1

• Mean Corpuscular Volume (MCV): 80-100 fL 1

  • Decreases in iron deficiency anemia
  • Reflects average red blood cell size 1

• Transferrin: 200-400 mg/dL 1

  • Increases proportionally to iron needs 1

Hair-Specific Iron Thresholds

Women with serum ferritin ≤30 ng/mL have a 21-fold increased risk of diffuse telogen hair loss compared to those with higher ferritin levels. 2 This threshold is critical because:

• Eight of nine patients with iron deficiency anemia (Hb <12 g/dL) had telogen hair loss 2
• Mean ferritin in women with hair loss was 16.3±12.6 ng/mL versus 60.3±50.1 ng/mL in controls 2
• Mean transferrin saturation was significantly lower in hair loss patients: 20.3±9.7% versus 28.3±11.8% 2
• TIBC was elevated in hair loss patients: 367.8±58.2 µg/dL versus 319.2±60.1 µg/dL 2

Important Clinical Caveats

Inflammation Confounds Ferritin Interpretation

• Ferritin is an acute-phase reactant and becomes falsely elevated during inflammation, infection, or illness 1, 4, 5
• In the presence of inflammation, ferritin up to 100 µg/L may still be consistent with iron deficiency 4
• Always measure C-reactive protein (CRP) alongside ferritin to identify concurrent inflammation 4
• Without inflammation, ferritin <30 µg/L definitively establishes iron deficiency 4

Test Variability and Timing

• Serum iron shows greater day-to-day variation than hemoglobin 1, 3
• Serum iron concentration increases after each meal 3
• Diurnal variation causes serum iron to rise in the morning and fall at night 3
• Do not rely on serum iron alone to exclude iron deficiency—it has poor diagnostic accuracy due to high variability 4

Optimal Diagnostic Approach

• Ferritin and transferrin saturation are the most reliable markers for assessing iron status 4, 6
• The simultaneous presence of low ferritin (<30 µg/L) and low TSAT (<16%) unequivocally confirms absolute iron deficiency 4
• Ferritin detects iron deficiency in many cases where serum iron and TIBC are not clearly diagnostic 6
• Normal serum iron and TIBC do not exclude iron deficiency 4

Treatment Targets for Hair Health

Once iron deficiency is identified and treated, aim for:

• Ferritin ≥100 ng/mL to ensure sufficient iron stores 4
• Transferrin saturation ≥20% to confirm adequate iron availability 4
• These targets exceed the minimum thresholds and provide optimal conditions for hair growth 4, 2

When to Consider Intravenous Iron

• Gastrointestinal intolerance to oral iron 4
• Chronic kidney disease with eGFR <30 mL/min/1.73 m² 4
• Lack of hematologic response after 4-8 weeks of adequate oral iron therapy 4