Genetics, hormones and stress get most of the blame for hair loss. But what you eat matters too. So which vitamin deficiency causes hair loss? Low levels of iron, vitamin D, vitamin B12 and zinc have all been linked to thinning hair, while a lack of biotin is a rarer cause.
Hair follicles are some of the busiest cells in your body.1 They need a steady supply of nutrients to keep making strong, healthy strands. This guide explains how deficiencies can affect your hair, which nutrients matter most, how to tell deficiency-related shedding from pattern hair loss, and when to get your levels checked.
Hair loss linked to a deficiency is often temporary. Once your levels are back on track, hair can start growing normally again.
How can vitamin deficiencies cause hair loss?
Every hair goes through three phases. There's anagen (growing), catagen (a short transition) and telogen (resting), after which the hair falls out and a new one starts.1
Your follicles need nutrients to build keratin, the protein that makes up each strand. When supplies run low, follicles can't keep up.2
A deficiency can also push more hairs into the resting phase early. They then shed a few months later, often all over the scalp rather than in one patch. This type of shedding is called telogen effluvium.2 The good news is that it's usually temporary once the cause is sorted.
Because hairs shed months after the trigger, the cause of thinning isn't always obvious. Think back to how you were eating and feeling a few months ago.
It's worth being clear about what nutrients can't do, though. They won't reverse male or female pattern hair loss, which is driven by genetics and hormones. For that, licensed treatments such as finasteride (for men) and Regaine can slow hair loss and help regrowth in many people. A pharmacist or prescriber can check whether one is suitable for you. Part of that is ruling out other causes of shedding, such as a deficiency.
Which vitamin deficiencies cause hair loss?
Research has linked several nutrients to hair health. Some links are stronger than others.
Iron
Iron deficiency is a recognised cause of hair shedding.3 Women who have heavy periods are more likely to run low on iron.
A 2013 study found that women with female pattern hair loss had lower levels of ferritin (the body's iron store) than women without hair loss.4 Low iron doesn't always cause hair loss on its own, but it may make existing thinning worse.
Vitamin D
Vitamin D has been studied for its role in hair health. A 2020 study found men with early-onset pattern hair loss tended to have lower vitamin D levels than men without it.5
That's a link, not proof that low vitamin D causes hair loss. Still, it's a nutrient many of us run low on in the UK, especially in autumn and winter.6
Vitamin B12
Your body needs B12 to make healthy red blood cells, which carry oxygen and nutrients around the body, including to your scalp. A 2022 study found people with long-term telogen effluvium were more likely to have low B12 levels.7
B12 comes mainly from meat, fish, eggs and dairy. That means vegans and some vegetarians are more likely to run short.
Zinc
Zinc plays a role in keratin production and tissue repair. Low zinc levels have been linked to several types of hair loss in research.2
Biotin
Biotin (vitamin B7) helps your body make keratin. True biotin deficiency is rare in people who eat a varied diet, and there's little evidence that extra biotin helps hair if your levels are already normal.2
More isn't always better. Very high intakes of some nutrients, such as vitamin A and selenium, can actually trigger hair shedding.
Research backs this up: excess vitamin A and selenium are both recognised causes of hair loss.2 So it's best to target a genuine gap rather than stacking supplements.
Is your hair loss caused by a deficiency or genetics?
The pattern of shedding gives you a good clue.
Deficiency-related hair loss usually shows up as thinning across the whole scalp. You might notice more hair in your brush or the shower drain. It often comes with other signs, such as tiredness, pale skin or brittle nails.
Genetic hair loss tends to follow a pattern. In men, it usually starts with a receding hairline at the temples or thinning at the crown. In women, the central parting tends to widen.
Shedding all over with tiredness points towards a deficiency. A receding hairline or thinning crown points towards pattern hair loss.
A GP can look at your hair and scalp, ask about your health and arrange blood tests if needed, such as iron, ferritin, vitamin D and B12. But finding a deficiency doesn't on its own prove it caused your hair loss.
Should you get nutrients from food or supplements?
Food should always come first. A varied diet with plenty of vegetables, wholegrains, protein and healthy fats covers most people's needs.
Dark leafy greens like spinach and kale, for example, provide folate, iron and vitamin K. Eggs, oily fish, beans, nuts and seeds are all good all-rounders.
But sometimes diet alone isn't enough.
- Vitamin D - the NHS advises everyone in the UK to consider a daily 10 microgram vitamin D supplement in autumn and winter, when sunlight is too weak for your skin to make enough.6 Vitamin D contributes to the normal function of the immune system. OneVit Vitamin D3 & K2 is one option.
- Vitamin B12 - if you eat little or no animal produce, a supplement such as OneVit B Complex can help. Vitamin B12 contributes to normal red blood cell formation.
- Biotin - biotin contributes to the maintenance of normal hair. But don't assume a hair supplement like OneVit Biotin will help. Get advice on what's causing your hair loss, and whether you have a genuine gap, first.
- Iron - iron contributes to the normal formation of red blood cells and haemoglobin. Only take iron supplements long term if a test shows you need them.
Having a blood test? Tell the clinician and the lab about any supplements you take, especially biotin, as it can affect some test results. Follow their advice on whether and when to pause it.8
For a full rundown of nutrients and where to find them, see our A-Z of vitamins and minerals.
When should you see a GP about hair loss?
Speak to a GP if:
- Your hair is falling out suddenly or in clumps
- Your hair has been noticeably thinning for several months
- You have bald patches
- You also feel tired, dizzy or short of breath, or notice changes to your skin or nails
- Hair loss is affecting your confidence or wellbeing
Tiredness, dizziness and hair loss together can be a sign of anaemia. It's worth getting a blood test rather than guessing.
A GP can arrange blood tests and help work out whether a deficiency, a thyroid problem or something else is behind it.3
Frequently asked questions
Does biotin help hair growth?
Biotin contributes to the maintenance of normal hair, so getting enough matters. But true biotin deficiency is rare, and there’s little evidence that extra biotin helps your hair if your levels are already normal. If you eat a varied diet, you’re probably getting enough. Before trying a supplement, it’s worth getting advice on what’s causing your hair loss and whether you have a genuine gap. If you’re having a blood test, tell the clinician you take biotin, as it can affect some results.
What vitamins are good for hair loss?
No vitamin can reverse pattern hair loss, but some nutrients play a part in keeping hair healthy. Biotin and zinc contribute to the maintenance of normal hair, while iron, vitamin D and B12 are often checked when someone has unexplained shedding. It’s best to fix a genuine shortfall, ideally confirmed by a blood test, rather than taking lots of supplements.
What vitamin deficiency causes fatigue and hair loss?
Low iron is the most common culprit when tiredness and hair shedding appear together, as it can lead to anaemia. Low vitamin B12 can cause similar symptoms. Both affect how well your body makes healthy red blood cells. If you feel exhausted and you’re losing more hair than usual, ask a GP about a blood test.
Can low vitamin D and B12 cause hair loss?
Low levels of both have been linked to hair shedding in research, although studies show an association rather than proof that one causes the other. Vitamin D often runs low in the UK during autumn and winter, while B12 is more likely to be low if you eat little or no animal produce. A GP can test both.
Will my hair grow back after a deficiency is treated?
In most cases, yes. Shedding caused by a deficiency is usually temporary, and once your levels are back to normal, follicles can return to their usual growth cycle. It can take a few months to notice a difference, because hair grows slowly and new strands need time to come through.
References
- Murphrey MB, Agarwal S, Zito PM. Anatomy, Hair. StatPearls. 2023. ncbi.nlm.nih.gov
- Almohanna HM, Ahmed AA, Tsatalis JP, et al. The role of vitamins and minerals in hair loss: a review. Dermatology and Therapy. 2019;9(1):51-70. doi:10.1007/s13555-018-0278-6
- NHS. Hair loss. NHS website; 2023. nhs.uk
- Park SY, Na SY, Kim JH, et al. Iron plays a certain role in patterned hair loss. Journal of Korean Medical Science. 2013;28(6):934-938. doi:10.3346/jkms.2013.28.6.934
- Sanke S, Chander R, Jain A, et al. Study of serum vitamin D levels in men with premature androgenetic alopecia. International Journal of Dermatology. 2020. doi:10.1111/ijd.14982
- NHS. Vitamin D. NHS website; 2023. nhs.uk
- Mamatha P, Aparna K. Serum vitamin B12 in chronic telogen effluvium patients: a case-control study. Journal of Dermatology and Dermatologic Surgery. 2022. journals.lww.com
- Manchester University NHS Foundation Trust. Factors known to significantly affect performance of tests and interpretation of results. MFT website; 2026. mft.nhs.uk
This article is intended for informational purposes only and does not replace professional medical advice. Always read the patient information leaflet supplied with your medication and speak to a healthcare professional if you have specific concerns.