What Is the Connection Between Vitamin D and Hair Loss?

Vitamin D is widely known for its role in bone health, yet in recent decades researchers have explored another important question: does vitamin D influence hair growth and hair loss? Scientific evidence suggests that vitamin D plays a role in the regulation of hair follicles, and that deficiency may be associated with certain forms of hair loss. However, the relationship is complex. Not all hair loss is caused by low vitamin D, and supplementation is not always a guaranteed solution. This article explains what research shows, how studies were conducted, what their limitations are, and how real users have interpreted this evidence.

Understanding Vitamin D and the Hair Follicle

Vitamin D is a fat-soluble vitamin that functions more like a hormone than a typical vitamin. After being produced in the skin through sunlight exposure or absorbed from food, it is converted in the liver and kidneys into its active form, calcitriol. This active form binds to a structure in cells called the vitamin D receptor, often abbreviated as VDR.

Hair grows from structures in the skin called hair follicles. Each follicle goes through repeating cycles: a growth phase called anagen, a transitional phase called catagen, and a resting phase called telogen. Research has shown that vitamin D receptors are expressed in keratinocytes, the main cells forming the outer layer of the skin, and in dermal papilla cells, which regulate hair growth. When these receptors do not function properly, hair cycling can be disrupted.

One of the most influential studies examining this mechanism was conducted in 1994 by Li and colleagues. In this animal study, researchers created genetically modified mice that lacked the vitamin D receptor. The population consisted of laboratory mice observed over several months. The researchers evaluated hair growth visually and through microscopic examination of skin tissue. The mice developed alopecia, meaning hair loss, despite having normal calcium levels. The study concluded that the vitamin D receptor is essential for normal hair follicle cycling. A major strength of this study was its controlled experimental design. However, it was conducted in animals, not humans, and genetic knockout models do not perfectly replicate common human vitamin D deficiency. Therefore, while it demonstrates biological plausibility, it does not prove that low vitamin D alone causes hair loss in people.

Vitamin D Deficiency and Alopecia Areata

Alopecia areata is an autoimmune disease in which the immune system mistakenly attacks hair follicles, causing patchy hair loss. Several human studies have investigated vitamin D levels in individuals with this condition.

In 2014, Aksu Cerman and colleagues conducted a case-control study published in the International Journal of Dermatology. The study included 86 patients diagnosed with alopecia areata and 58 healthy controls. Blood samples were taken at a single time point to measure serum 25-hydroxyvitamin D levels, which is the standard laboratory marker of vitamin D status. The results were evaluated by comparing average vitamin D levels between groups using statistical analysis. The researchers found significantly lower vitamin D levels in patients with alopecia areata compared to controls. Because this was a cross-sectional study, there was no long-term follow-up period. The main limitation is that the design cannot determine causation. It is unclear whether vitamin D deficiency contributes to the disease or whether inflammation or lifestyle factors associated with the disease reduce vitamin D levels.

A 2017 systematic review and meta-analysis by Lee and colleagues published in the Journal of the American Academy of Dermatology analyzed multiple observational studies on vitamin D and alopecia areata. A meta-analysis combines data from several studies to increase statistical power. The population included several hundred patients across different countries. The method involved pooling serum vitamin D levels and calculating overall differences between patients and controls. The review concluded that vitamin D levels were significantly lower in individuals with alopecia areata. The strength of a meta-analysis is its broader data set. However, the authors noted heterogeneity between studies, meaning differences in measurement methods, population characteristics, and definitions of deficiency. These differences reduce certainty about the magnitude of the association.

Overall, research supports a consistent association between vitamin D deficiency and alopecia areata, but interventional trials testing whether supplementation reverses hair loss remain limited and small.

Vitamin D and Androgenetic Alopecia

Androgenetic alopecia, also known as male or female pattern hair loss, is the most common cause of hair thinning. It is primarily driven by genetic sensitivity to dihydrotestosterone, commonly abbreviated as DHT. Researchers have investigated whether vitamin D plays a secondary role in this condition.

In 2020, a review published in Dermatologic Therapy evaluated studies examining vitamin D levels in patients with androgenetic alopecia. The review included observational studies in which blood vitamin D levels were measured in men and women with patterned hair loss. Most studies were cross-sectional and measured serum 25-hydroxyvitamin D levels at one visit. The evaluation methods included statistical comparisons between patients and healthy controls and correlation analyses between vitamin D levels and severity scales such as the Hamilton–Norwood scale in men. Several studies reported lower vitamin D levels in affected individuals. However, results were not entirely consistent across all populations.

The primary criticism of this body of research is that most studies are observational and cross-sectional. They do not follow patients over time, and they do not test whether correcting deficiency improves hair density. Furthermore, vitamin D deficiency is common in the general population, which makes it difficult to determine whether the deficiency is specific to hair loss or simply coincidental.

Interventional Studies and Supplementation

While associations exist, the critical question is whether supplementing vitamin D improves hair growth. Interventional studies are more limited.

Some small pilot studies have explored topical vitamin D analogs, particularly in alopecia areata. These studies generally involve small groups of patients treated for several months and evaluated using clinical photography and severity scoring systems such as the Severity of Alopecia Tool. Results have been mixed. Some patients experienced regrowth, while others did not respond. Limitations include small sample sizes, lack of placebo control groups, and short follow-up durations.

Large randomized controlled trials, which are considered the gold standard in medical research, are still lacking for vitamin D supplementation in androgenetic alopecia. Without these trials, it is not scientifically accurate to claim that vitamin D supplementation alone reverses common pattern baldness.

Biological Mechanisms: Why Vitamin D Might Matter

Laboratory research suggests that vitamin D signaling influences keratinocyte differentiation, meaning how skin cells mature and organize. It also appears to regulate immune function. Because alopecia areata involves immune dysregulation, and because hair follicle cycling depends on properly functioning keratinocytes and dermal papilla cells, vitamin D may serve as a regulatory factor.

However, androgenetic alopecia is primarily driven by DHT sensitivity. According to research summarized on Tressless and related scientific literature, DHT binds to androgen receptors in hair follicles, gradually shrinking them in genetically susceptible individuals. Vitamin D does not block DHT. Therefore, even if deficiency is corrected, the underlying androgen sensitivity may persist.

USER EXPERIENCES

The Tressless community includes numerous discussions about vitamin D testing and supplementation. Community posts reveal that many users discover low vitamin D levels during routine blood tests and begin supplementation. Some report improvements in hair shedding over several months, particularly if they were severely deficient. Others report no noticeable change.

Community sentiment generally reflects scientific findings: vitamin D may support overall scalp health, especially in cases of documented deficiency, but it is rarely viewed as a standalone solution for androgenetic alopecia. Many users combine vitamin D supplementation with treatments such as finasteride, minoxidil, ketoconazole shampoo, and microneedling, which target DHT or directly stimulate follicles. Discussions often emphasize the importance of blood testing before supplementation, as excessive vitamin D intake can cause toxicity.

These user experiences align with research suggesting that vitamin D is supportive rather than curative in most cases of common hair loss.

So, What Is the Connection?

The connection between vitamin D and hair loss is supported by biological plausibility and consistent observational evidence, especially in alopecia areata. Vitamin D receptors are essential for normal hair follicle cycling, as demonstrated in animal models. Human studies show that individuals with certain types of hair loss often have lower vitamin D levels compared to healthy controls. However, current research does not definitively prove that vitamin D deficiency directly causes common pattern baldness, nor does it confirm that supplementation alone reliably restores hair growth.

In practical terms, correcting a confirmed deficiency is reasonable and medically appropriate for overall health. Yet for androgenetic alopecia, treatments targeting DHT remain the most evidence-based options. Vitamin D appears to be a contributing factor in some contexts, but not the primary driver of most cases of hair loss.

References

Aksu Cerman, A., Sarikaya Solak, S., & Kivanc Altunay, I. (2014). Vitamin D deficiency in alopecia areata. International Journal of Dermatology, 53(12), 1523–1527. https://pubmed.ncbi.nlm.nih.gov/24655364/

Lee, S., Kim, B. J., Lee, Y. B., Lee, W. S., & Kim, D. W. (2017). Vitamin D levels in alopecia areata: A systematic review and meta-analysis. Journal of the American Academy of Dermatology, 77(4), 768–774. https://pubmed.ncbi.nlm.nih.gov/28734728

Li, Y. C., Pirro, A. E., Amling, M., Delling, G., Baron, R., Bronson, R., & Demay, M. B. (1994). Targeted ablation of the vitamin D receptor: An animal model of vitamin D–dependent rickets type II with alopecia. Nature, 371(6498), 507–511. https://pubmed.ncbi.nlm.nih.gov/7935768/]

Saini, K., Mysore, V., & Chandrashekar, B. (2020). Role of vitamin D in hair loss: A short review. Dermatologic Therapy, 33(6), e13773. https://pubmed.ncbi.nlm.nih.gov/32786173/

Tressless Community. (n.d.). Vitamin D discussions and user experiences. https://tressless.com/search/vitamin%20D