Hair loss can be distressing, and when it happens, many people immediately wonder whether a vitamin deficiency could be the cause. Among the nutrients frequently discussed, vitamin B12 often appears in online forums, medical consultations, and supplement advertisements. But how can you truly tell whether your hair loss is related to low vitamin B12 levels? The answer requires understanding what vitamin B12 does in the body, how deficiency presents clinically, and what scientific studies have actually shown about its relationship to hair growth.

Understanding What Vitamin B12 Actually Does

Vitamin B12, also called cobalamin, is a water-soluble vitamin essential for DNA synthesis, red blood cell production, and proper nerve function. DNA synthesis refers to the process by which cells copy their genetic material in order to divide. This is crucial for tissues that renew rapidly, including bone marrow, intestinal lining, and hair follicles.

Hair follicles are among the fastest dividing structures in the human body. Each hair strand grows from a follicle that cycles through growth, rest, and shedding phases. During the growth phase, known as anagen, cells divide rapidly to produce the hair shaft. Because vitamin B12 is required for proper DNA replication, severe deficiency can disrupt this process.

According to the National Institutes of Health Office of Dietary Supplements, vitamin B12 deficiency most commonly results from malabsorption, pernicious anemia, gastrointestinal surgery, certain medications, or strict vegan diets without supplementation. Symptoms typically include fatigue, weakness, numbness, memory issues, and a specific type of anemia called megaloblastic anemia, in which red blood cells become abnormally large due to impaired DNA synthesis. Hair loss is not considered a primary symptom by major public health authorities such as the NIH or WHO, but dermatologic changes have been documented in medical literature.

What the Research Says About Vitamin B12 and Hair Changes

Scientific evidence shows that vitamin B12 deficiency can affect hair, but the relationship is specific and not always related to typical pattern baldness.

A 1986 case study published in Archives of Dermatology described a patient with pernicious anemia and vitamin B12 deficiency who developed generalized skin hyperpigmentation and premature white hair. The study involved a single adult patient and evaluated results through clinical examination and laboratory confirmation of low B12 levels. After treatment with intramuscular cyanocobalamin injections, pigmentation and hair color normalized. The duration of follow-up extended several months after therapy initiation. The limitation of this study is that it involved only one patient, which means the findings cannot be generalized to the broader population. However, it demonstrates that B12 deficiency can influence hair pigmentation and that these changes may be reversible with treatment.

A similar 2008 case report in Acta Dermato-Venereologica described a 21-year-old vegetarian woman with confirmed vitamin B12 deficiency. She presented with hyperpigmentation and increased melanocytes, which are pigment-producing cells. Diagnosis was confirmed through blood testing, and improvement occurred after both intramuscular and oral B12 supplementation. The evaluation included laboratory measurements and skin biopsy analysis. As with most case reports, the sample size was one individual, which limits broad conclusions. Still, it confirms that vitamin B12 deficiency can manifest with dermatologic and hair changes.

When it comes to hair loss specifically, larger observational studies provide more clarity. A 2009 study published in the Indian Journal of Dermatology, Venereology and Leprology examined serum vitamin B12, folate, ferritin, and iron levels in Turkish patients with alopecia areata. Alopecia areata is an autoimmune form of hair loss characterized by patchy bald spots. The study included patients diagnosed clinically with alopecia areata and compared them with healthy controls. Blood samples were analyzed for vitamin levels. The results showed no significant difference in vitamin B12 levels between patients and controls. The study suggests that B12 deficiency is not strongly associated with alopecia areata. A limitation is that the study population was geographically limited, and it focused only on one type of hair loss.

A 2012 study published in Cutaneous and Ocular Toxicology evaluated serum holotranscobalamin, vitamin B12, folic acid, and homocysteine levels in patients with alopecia areata. Holotranscobalamin is the active fraction of vitamin B12 circulating in the blood. This case-control study measured blood markers in diagnosed patients compared to healthy individuals. Although some biochemical differences were noted, vitamin B12 deficiency was not established as a primary cause of alopecia areata. As with many observational studies, the design cannot prove cause and effect.

Importantly, there is little high-quality evidence linking vitamin B12 deficiency to androgenetic alopecia, also known as male or female pattern hair loss. Androgenetic alopecia is primarily driven by genetic sensitivity to dihydrotestosterone, a derivative of testosterone. According to extensive research summarized in Tressless and broader dermatological literature, dihydrotestosterone miniaturizes hair follicles over time. Vitamin B12 deficiency does not act through this hormonal pathway.

Because vitamin B12 deficiency produces systemic symptoms, hair loss alone is rarely the only sign. If hair shedding is accompanied by fatigue, pale skin, shortness of breath, numbness in hands or feet, memory difficulties, or tongue soreness, deficiency becomes more plausible. Blood testing is essential for confirmation. Serum vitamin B12 levels are typically measured in picograms per milliliter. Levels below approximately 200 pg/mL are generally considered deficient, although thresholds vary slightly by laboratory.

Another potential indicator is premature graying. The 2017 retrospective analysis of 71 patients with premature canities, published in the Indian Journal of Dermatology, found associations between low serum vitamin B12 and early graying. The study evaluated medical records and laboratory results of patients presenting with premature gray hair. While the association was statistically significant, the design was retrospective, meaning researchers looked back at existing data rather than conducting a controlled trial. Therefore, causation cannot be firmly established.

In contrast, if your hair loss follows a predictable pattern, such as gradual thinning at the temples or crown in men, or widening of the central part in women, and you do not have systemic symptoms, androgenetic alopecia is statistically far more likely than vitamin deficiency.

user experiences

Within the Tressless community, discussions about vitamin B12 frequently appear in posts where users share blood test results showing low B12 levels along with hair thinning. In several threads, users reported supplementing with B12 after discovering laboratory-confirmed deficiency. Some individuals noted improvement in overall well-being, including energy levels, but many reported that hair regrowth was minimal unless they also addressed androgen-related hair loss using treatments such as finasteride or minoxidil.

Community discussions often highlight an important distinction: correcting a deficiency may improve hair health if deficiency is present, but supplementation beyond normal levels does not appear to enhance growth in individuals who are not deficient. Several users describe combining B12 with standard androgenic alopecia treatments. The broader consensus in community discussions aligns with published research: vitamin deficiencies can contribute to hair shedding in specific contexts, particularly telogen effluvium, but they are rarely the sole cause of pattern baldness.

How to Confirm Whether B12 Is the Cause

The only reliable way to determine whether your hair loss is related to vitamin B12 is through laboratory testing interpreted by a healthcare professional. Evaluation typically includes serum vitamin B12, complete blood count to assess for megaloblastic anemia, and sometimes homocysteine or methylmalonic acid levels, which can be elevated in deficiency.

If deficiency is confirmed and hair shedding improves after supplementation over several months, a causal relationship becomes more likely. However, if hair loss persists despite normalization of B12 levels, another cause should be investigated. Dermatologists often assess hair loss through scalp examination, dermoscopy, medical history, and sometimes scalp biopsy.

The Bottom Line: Is Your Hair Loss from Low B12?

Research shows that vitamin B12 deficiency can cause changes in hair pigmentation and may contribute to diffuse shedding in the context of systemic illness. However, it is not a common cause of androgenetic alopecia, the most prevalent form of hair loss in both men and women. The strongest indicators of B12-related hair changes include confirmed laboratory deficiency accompanied by systemic symptoms and improvement after correction.

If you suspect deficiency, testing is straightforward and treatment is effective when needed. But if your hair loss pattern matches genetic thinning and you have no signs of anemia or neurological symptoms, vitamin B12 is unlikely to be the primary cause.

References

Aaron, S., et al. (1986). Reversible hyperpigmentation of skin and nails with white hair due to vitamin B12 deficiency. Archives of Dermatology, 122(8), 896–899. https://doi.org/10.1001/archderm.122.8.896

Bhat, Y. J., et al. (2017). Demographic characteristics and association of serum vitamin B12, ferritin and thyroid function with premature canities in Indian patients: A retrospective analysis of 71 cases. Indian Journal of Dermatology, 62(3), 304–308. https://pubmed.ncbi.nlm.nih.gov/28584374

Karadag, A. S., et al. (2009). Serum vitamin B12, folate, ferritin, and iron levels in Turkish patients with alopecia areata. Indian Journal of Dermatology, Venereology and Leprology, 75(5), 552–555. https://pubmed.ncbi.nlm.nih.gov/19736464

Korkmaz, S., et al. (2012). Serum holotranscobalamin, vitamin B12, folic acid and homocysteine levels in alopecia areata patients. Cutaneous and Ocular Toxicology, 31(3), 221–224. https://pubmed.ncbi.nlm.nih.gov/22591107/

National Institutes of Health Office of Dietary Supplements. (2022). Vitamin B12 fact sheet for health professionals. https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional

Tressless Community. (2021). My Vitamin D levels came <4.20 ng/ml and B12 came 184 pg/ml. https://reddit.com/r/tressless/comments/oiqj84/my_vitamin_d_250h_levels_came_420_ngml_20_implies

Tressless Community. (2025). B12 deficiency hairloss (hair thinning). https://reddit.com/r/tressless/comments/1mtq8qy/b12_deficiency_hairloss_hair_thinning

Tressless Community. (2019). Did anyone see a difference in hair growth after correcting a folic acid deficiency? https://reddit.com/r/tressless/comments/d6tuyh/did_anyone_see_a_difference_in_hair_growth_after

Wong, S. S., et al. (2008). Skin hyperpigmentation and increased angiogenesis secondary to vitamin B12 deficiency in a young vegetarian woman. Acta Dermato-Venereologica, 88(4), 425–426. https://pubmed.ncbi.nlm.nih.gov/18311462