Can low ferritin levels contribute to hair shedding and affect hair growth?

Can Ferritin Levels Affect Hair Shedding and Growth?

Yes, low ferritin levels are associated with hair shedding and impaired hair growth, particularly in women with chronic diffuse telogen hair loss, androgenetic alopecia, and alopecia areata, and iron supplementation should be initiated when ferritin is <60 ng/mL in the context of hair loss. 1, 2

The Biological Mechanism

Iron serves as a cofactor for ribonucleotide reductase, the rate-limiting enzyme in DNA synthesis, making it essential for hair follicles which have extremely high cellular turnover rates. 3 This explains why iron deficiency can directly impair the hair growth cycle and lead to increased shedding.

Diagnostic Thresholds and Testing

Order CBC, serum ferritin, TSH, and transferrin saturation as baseline tests for any woman presenting with hair loss. 1, 4

Interpreting Ferritin Levels:

• Ferritin <60 ng/mL warrants iron supplementation in the context of hair loss, even without anemia 1, 4, 2
• Ferritin ≤15 μg/L confirms iron deficiency with 98% specificity in premenopausal women 1
• Without inflammation, ferritin <30 μg/L defines iron deficiency 1
• The adequate ferritin level for hair growth is 40-60 ng/mL, which corresponds to hemoglobin levels of 13.1-13.8 g/dL 2

Critical Caveat - Ferritin as an Acute-Phase Reactant:

Always assess inflammatory markers (CRP, ESR) alongside ferritin because ferritin can be falsely elevated during infection, inflammation, malignancy, or liver damage, potentially masking true iron deficiency. 1, 4 With inflammation present, the lower limit of normal ferritin increases to 100 μg/L. 1 If ferritin appears "normal" but microcytic anemia or low MCV is present, check transferrin saturation and serum iron/TIBC to confirm iron status. 4

Evidence for Different Types of Hair Loss

Strong Evidence:

• Androgenetic alopecia: Mean ferritin levels are significantly lower (37.3 ng/mL) compared to controls without hair loss (59.5 ng/mL) 5
• Telogen effluvium: Multiple studies found lower ferritin levels in patients with diffuse hair loss 1, 3
• Iron deficiency accounted for 70.3% of female alopecia cases in a 2023 study of 155 patients 2

Conflicting Evidence:

• Alopecia areata: Only 2 of 8 studies supported an association between iron deficiency and alopecia areata 6, 1
• The discrepancy appears related to sex differences—studies supporting the association were primarily in female subjects 6, 1
• The British Association of Dermatologists does not recommend routine iron testing for alopecia areata due to conflicting evidence 1, 4
• One 2002 study found no direct relationship between low serum ferritin (≤20 μg/L) and chronic diffuse telogen hair loss, with iron supplementation failing to reverse hair loss in 5 women 7

Treatment Approach

Initiate iron supplementation when ferritin is <60 ng/mL in the context of hair loss, aiming for ferritin ≥60 ng/mL with corresponding hemoglobin ≥13.0 g/dL. 1, 2

Timing Matters:

Iron supplementation started within 6 months of hair loss onset results in better prognosis. 1, 4, 2 Disease duration is an important prognostic factor for improvement of serum ferritin levels. 2 Hair loss due to iron deficiency develops gradually over months, not acutely. 1

Monitoring:

Monitor ferritin and hemoglobin every 3 months after starting supplementation. 1 Patients with subjective improvement of hair regrowth had greater increases in ferritin levels after iron supplementation. 2

Additional Workup for Unexplained Iron Deficiency

Consider tissue transglutaminase (TTG) antibodies if unexplained iron deficiency is found to rule out celiac disease. 1, 4 This is important because celiac disease can cause malabsorption leading to refractory iron deficiency.

Common Pitfalls to Avoid

• Do not rely on ferritin alone without checking inflammatory markers, as inflammation can mask true iron deficiency 1, 4
• Do not use anemia as the sole criterion for iron deficiency in hair loss—the corresponding ferritin level for female anemia (Hb: 12.0 g/dL) is only 5.1 ng/mL, far lower than the adequate level for hair growth (40-60 ng/mL) 2
• Do not delay iron supplementation beyond 6 months of hair loss onset, as earlier treatment yields better outcomes 1, 4, 2
• Recognize that nutrient deficiencies accounted for 83.9% of female alopecia cases, with iron deficiency being the most common, so a complete nutritional survey is essential 2