Which serum vitamin levels are associated with hair loss?

Vitamin Levels Associated with Hair Loss

Vitamin D deficiency is the most consistently and strongly associated vitamin deficiency with hair loss across multiple types of alopecia, followed by iron (ferritin), zinc, and to a lesser extent vitamin B complex. 1, 2

Primary Vitamin Deficiencies Linked to Hair Loss

Vitamin D (Most Robust Evidence)

Low serum 25-hydroxyvitamin D [25(OH)D] levels show the strongest association with hair loss, particularly in alopecia areata (AA), androgenetic alopecia (AGA), and telogen effluvium (TE). 1, 2

• Deficiency threshold: Serum 25(OH)D <20 ng/mL (or <50 nmol/L)
• Meta-analysis findings: Patients with non-scarring alopecia have serum 25(OH)D levels approximately 7-8.5 ng/dL lower than controls 2, 3
• Prevalence: 70-86% of AA patients demonstrate vitamin D deficiency versus 25% in controls 1
• Severity correlation: Lower vitamin D levels inversely correlate with increasing severity of hair loss (measured by SALT score, P < 0.001, r = −0.41) 1
• Mechanism: Vitamin D receptor (VDR) is critical for hair follicle cycling; VDR knockout mice develop complete alopecia by 8 months 1

The evidence is particularly strong for alopecia areata, with five case-control studies consistently demonstrating this association 1. A 2024 meta-analysis of 3,374 patients confirmed both decreased serum levels and 3.11-fold increased odds of vitamin D deficiency in non-scarring alopecia 2.

Iron (Ferritin) - Mixed but Important Evidence

Iron deficiency shows association with hair loss, particularly chronic diffuse telogen effluvium, though evidence is more conflicting than vitamin D. 1

• Marker: Serum ferritin (reflects total iron storage)
• Evidence quality: Only 2 of 8 studies in AA showed clear association 1
• Gender difference: Association appears stronger in females than males 1
• Key finding: Lower ferritin in women with AA and AGA compared to controls, but NOT in telogen effluvium or alopecia totalis/universalis 1

Important caveat: Despite iron being the most common nutritional deficiency worldwide, the 2005 Trost review concluded there was insufficient evidence to recommend routine screening for iron deficiency in hair loss patients 1. However, when deficiency is present, particularly in women with chronic diffuse hair loss, it warrants correction.

Zinc - Consistent Association, Limited Treatment Data

Lower serum zinc levels are consistently found in AA patients compared to controls, with inverse correlation to disease severity. 1

• Most studies identify lower serum zinc in AA patients
• Serum levels inversely associated with severity of disease 1
• Critical limitation: Paucity of double-blind trials using zinc as monotherapy 1
• Combination therapy studies show promise but cannot isolate zinc's effect

B Vitamins (Biotin/B7, Pantothenic Acid/B5, Folate/B9)

B vitamins show emerging evidence but less robust than vitamin D. 4, 5

• Vitamin B complex appears to play a role in hair growth and maintenance 4
• Combination supplements containing biotin and pantothenic acid show clinical benefit 5
• Lower vitamin B9 (folate) levels found in more severe female pattern hair loss, though not independent after demographic adjustment 6

Minerals with Weaker or Conflicting Evidence

Copper, Magnesium, Selenium - Insufficient Evidence

Current evidence does NOT support routine assessment of these minerals. 1

• Only 1 of multiple studies showed lower copper in AA 1
• Magnesium: No consistent differences found 1
• Selenium: Conflicting results between Iranian (lower levels) and Finnish (no difference) studies 1
• Conclusion: Paucity of studies precludes conclusions about their role 1

Clinical Approach Algorithm

For patients presenting with hair loss:

1. Check serum 25(OH)D levels - strongest evidence, most consistent association

   • If <20 ng/mL: Supplement and monitor
   • Particularly important in alopecia areata, where deficiency correlates with severity

2. Check serum ferritin in women with chronic diffuse hair loss or AA

   • Evidence stronger in females than males
   • Consider supplementation if deficient, though treatment trials lacking

3. Consider zinc levels if other deficiencies ruled out

   • Consistent association but treatment evidence weak
   • May be more relevant in combination therapy

4. Do NOT routinely check copper, magnesium, or selenium

   • Insufficient evidence to support screening

5. B vitamin assessment may be considered in refractory cases

   • Evidence emerging but not yet definitive for routine use

Important Caveats

• No conclusive supplementation trials exist demonstrating that correcting vitamin D or other deficiencies definitively improves hair regrowth, despite strong associative evidence 1, 7
• Vitamin D deficiency may be an initiating factor rather than a maintaining factor in long-term disease 1
• Most studies are observational case-control designs, not randomized controlled trials
• High heterogeneity exists across studies in definitions of deficiency and patient populations 2, 3
• The role of the vitamin D receptor (VDR) may be more critical than the ligand itself 1