TLDR Vitamin D levels in hair don't match those in blood, so hair isn't a reliable indicator of Vitamin D status.
The study involved 26 healthy Caucasian young adults and aimed to determine the correlation between 25(OH)D3 (a form of Vitamin D) concentrations in serum and hair. The study found that 25(OH)D3 could be detected in human hair, but there was no correlation between serum and hair 25(OH)D3 concentrations. Factors such as gender, body mass index, supplementation, or sun exposure had no effects on hair 25(OH)D3 concentrations, but supplementation and sun exposure significantly increased serum 25(OH)D3 concentrations. The study concluded that while 25(OH)D3 can be detected in human hair, its use as a biomarker requires further investigation due to the lack of correlation with serum 25(OH)D3 concentrations.
4 citations
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May 2021 in “Molecules” The hair test for vitamin D could be a useful alternative to blood tests, providing a longer-term vitamin D status, but more research is needed.
378 citations
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February 2020 in “Nature Reviews Endocrinology” 
119 citations
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July 2016 in “Annals of the New York Academy of Sciences” Vitamin D has potential benefits for cancer prevention, heart health, diabetes, obesity, muscle function, skin health, and immune function, but clinical results are mixed and more research is needed.
567 citations
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October 2007 in “Clinical and investigative medicine” Hair cortisol can be used to measure long-term stress exposure.
January 2025 in “Scientific Reports” Hair analysis can show changes in vitamin D levels over time.
September 2023 in “Diagnostics” Low vitamin D levels may affect ovulation and progesterone in infertile women.
Vitamin D is crucial for skin health and managing skin diseases.
139 citations
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February 2014 in “Journal of Advanced Research” Vitamin D is important for skin health and may affect conditions like psoriasis and hair loss, but more research is needed to understand its role fully.
November 2020 in “Acta Scientific Women's Health” Low vitamin D levels can significantly contribute to hair loss, especially in women aged 35-45. Correcting these levels early may help prevent and treat this condition.
