Which Vitamin Deficiencies Cause Hair Loss?

Genetics, hormonal changes, and stress are well-understood causes of hair loss. But did you know that deficiencies in your diet can also cause it?

Hair follicles are among the most active cells in the body.^[1] They need a steady supply of nutrients to grow strong, healthy hair strands. When you lack these vitamins and minerals, it can cause temporary hair loss^[2], as the follicles do not get the nutrients they need to grow and maintain hair.

This article explains which vitamin deficiencies can cause hair loss, and how being deficient in nutrients can lead to you losing more hair. We’ve also highlighted some of the best nutritional supplements to support healthy and resilient hair.

How vitamin deficiencies can lead to hair loss

Nutrient deficiencies can lead to hair loss by affecting our hair follicles’ ability to make new cells.^[3]

Hair goes through three phases: anagen (growth), catagen (transitional), and telogen (resting).^[4]

Without enough nutrients, hair cannot produce proteins like keratin, which is essential to grow new strands and keep hair strong. A deficiency can also push hair into the telogen (resting) phase earlier, where hair can shed more easily. It also reduces the time hair spends in the anagen (growth) phase.

However, while vitamins and nutrients are vital for hair growth, they cannot completely prevent hair loss or treat underlying conditions. Finasteride and Regaine are the only proven treatments that can help stop hair loss caused by pattern baldness and encourage hair regrowth.

Which vitamin deficiencies cause hair loss?

Deficiencies in vitamin D, vitamin B12, and biotin (vitamin B7) are linked to hair loss. Being deficient in iron and zinc can also cause hair loss, as these minerals contribute to hair health and growth.

A 2020 study in the International Journal of Dermatology found that low vitamin D levels were linked to premature androgenetic alopecia, a hair-shedding condition in men.^[5]

Iron deficiency is also associated with diffuse hair shedding, especially in women of reproductive age. A 2013 study in the Journal of Korean Medical Science found that women with chronic hair loss had significantly lower ferritin (iron storage) levels compared with controls. Increasing their ferritin to regular levels resulted in improved hair density.^[6]

While this research does not suggest that iron or vitamin D deficiencies directly cause hair loss, both studies found that low levels of either nutrient were linked to poor hair health.

Preventing vitamin deficiencies: diet, supplements, or both?

It’s recommended to try to get as many nutrients as possible from your diet, but this is not always possible or easy.

For example, it’s hard for your body to produce enough vitamin D in the autumn and winter. This is especially true in the Northern Hemisphere, as sunlight exposure is much lower.^[7]

Vitamin D is an essential nutrient for hair growth, so taking a supplement such as OneVit Vitamin D3 & K2 is recommended, especially for people in the UK. This helps you get enough vitamin D during the shorter days.

Health conditions, such as allergies or intolerances to certain foods, can limit the sources of nutrients you can eat. This can make it harder to reach daily requirements through diet alone.

Supplements can be a convenient way to target any nutritional gaps. But the food you eat should still be the primary source of vitamins and minerals. It’s best to prioritise eating foods that are high in nutrients and contain a variety of them.

For example, dark leafy greens like spinach and kale contain vitamins A, C, E, and K as well as a range of B vitamins.

For a full list of vitamins and how you can increase your intake of them, read our A-Z of Vitamins and Minerals.

Hair loss and vitamins FAQs

Does low vitamin B12 cause hair shedding or slow regrowth?

Some research suggests that vitamin B12 deficiency is associated with diffuse hair loss.^[8] Diffuse hair loss refers to thinning across the entire scalp. This differs from male or female pattern baldness, where hair loss typically happens in the same places - at the temples and crown for men and the centre parting for women.

Vitamin B12 is needed to create new red blood cells, which carry oxygen and nutrients to the scalp and hair follicles.

When levels are low, follicles receive fewer nutrients and hair may grow more slowly or shed more easily.

Vitamin B12 is naturally found in meat, dairy products, and fish. It can be hard for vegetarians and vegans to get vitamin B12, as plant-based sources are limited.

Taking a dietary supplement containing vitamin B12, such as OneVit B Complex, can be beneficial if your intake is low.

Is biotin effective for treating hair loss?

Biotin, also known as vitamin B7, is needed to produce keratin, the protein that forms hair’s structure. Increasing your biotin levels can be beneficial for hair health and may help improve the hair’s resilience and growth.

Meat, fish, and eggs are good sources of biotin. Legumes, nuts and seeds and vegetables such as sweet potatoes and broccoli, are also high in biotin - ideal if you follow a plant-based diet.

You can also consider a targeted supplement to increase your biotin intake. Our pharmacists recommend OneVit Biotin, which contains 10,000µg (micrograms) of biotin and can help prevent deficiencies.

How can you tell if your hair loss is caused by a nutritional deficiency or genetics?

Hair loss caused by deficiencies typically presents as thinning across the whole scalp. Hair can feel finer and shed more when washed or brushed excessively. It often develops gradually, and other symptoms such as tiredness, pale skin, and brittle nails can appear alongside hair loss.

In comparison, genetic or hereditary hair loss tends to follow a pattern. Hair begins to recede at the temples or around the crown in men. In women, the central parting tends to widen, but can also present as thinning across the entire scalp.

A GP can arrange blood tests that detect iron, vitamin D, and B12 levels, which can help show whether a deficiency is contributing to hair loss.

When should you see a doctor about deficiencies and hair loss?

You should see your GP if you notice persistent or sudden hair shedding, or if your hair feels noticeably thinner over several months.

This is especially important if you also experience fatigue, dizziness, or changes to your skin or nails, which can indicate an iron or B12 deficiency.

Clinical sources

1. Murphrey MB, Agarwal S, Zito PM. Anatomy, Hair. StatPearls, 2023. [Accessed 05/11/2025]
2. Telogen Effluvium. Cleveland Clinic, 2025. [Accessed 05/11/2025]
3. Almohanna, H. M., Ahmed, A. A., Tsatalis, J. P., & Tosti, A. Role of Vitamins and Minerals in Hair Loss: A Review. Dermatology and therapy, 2019. [Accessed 05/11/2025]
4. B.D. Gaudette. HAIR | Overview. Encyclopedia of Forensic Sciences, 2000. [Accessed 05/11/2025]
5. Sanke S, Chander R, Jain A, Garg T, Bhatnagar A. Study of serum vitamin D levels in men with premature androgenetic alopecia. International Journal of Dermatology, 2020. [Accessed 05/11/2025]
6. Park SY et al. Iron plays a certain role in patterned hair loss. Journal of Korean Medical Science, 2013. [Accessed 15/09/2025]
7. Huotari A, Herzig KH. Vitamin D and living in northern latitudes--an endemic risk area for vitamin D deficiency. Int J Circumpolar Health, 2008. [Accessed 05/11/2025]
8. Mamatha P, Aparna K. Serum Vitamin B12 in Chronic Telogen Effluvium Patients: A Case–Control Study. Journal of Dermatology and Dermatologic Surgery, 2022. [Accessed 05/11/2025]

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