Which Vitamin Deficiencies Cause Hair Loss?
Last reviewed on 6 August 2026. We review our treatment guides every six months to keep them accurate.
Can a vitamin deficiency cause hair loss? Yes, it can, and if you have searched for which vitamin deficiencies cause hair loss you are asking a sensible question. A genuine shortfall of certain nutrients can trigger hair to shed, and correcting a real deficiency often lets the hair recover. The honest, evidence-based picture is narrower than the supplement adverts suggest, though. When a deficiency does cause hair loss it usually shows as a diffuse thinning or increased shedding all over the scalp, not the receding hairline or crown thinning of genetic pattern baldness, and for most people on a reasonably balanced diet a deficiency is not the cause at all.
For a plain, independent and regularly updated overview of what each nutrient does and how much you actually need, the NHS guide to vitamins and minerals is a good starting point. It makes the key point clearly: most people should get all the nutrients they need from a varied and balanced diet.
It is worth being honest up front that hair loss is very often not about vitamins. Genetics, thyroid problems, stress, a recent illness, pregnancy, crash dieting and certain medications are all common causes, and a sudden all-over shed frequently turns out to be a telogen effluvium rather than a vitamin problem. So this page answers which deficiencies genuinely matter and how to tell, while our separate guide on whether hair vitamins actually work covers the different question of whether taking supplements helps. Please treat this as general information and speak to your GP about your own situation.
Which vitamin and mineral deficiencies actually cause hair loss
The deficiencies with the best evidence are iron (the most common and important), vitamin D, zinc, and vitamin B12 and folate.
A short list of nutrients has the best evidence behind it. Each one matters as a genuine deficiency to correct, confirmed by a blood test, rather than as a routine top-up.
Iron (ferritin): the most common and most important. Iron deficiency is the world's most common nutritional deficiency and a well-recognised cause of hair loss, especially in women, where heavy periods and pregnancy are frequent causes. It is measured through ferritin, your iron stores, as well as a full blood count. The NHS lists hair loss among the symptoms of iron deficiency anaemia. Our guide on iron deficiency and hair loss covers this in detail.
Vitamin D. Low vitamin D has been associated with several types of hair loss, including telogen effluvium and the patchy autoimmune condition alopecia areata. Deficiency is common in the UK because we cannot make enough from sunlight between October and early March, which is why the NHS advises considering a daily supplement over autumn and winter. See our vitamin D and hair loss guide.
Zinc. A genuine zinc deficiency can cause shedding, and studies find lower zinc levels across several types of hair loss. There is an important twist, covered in our zinc and hair loss guide: both too little and too much zinc can be a problem, so this is not one to self-prescribe at high doses.
Vitamin B12 and folate. These B vitamins are part of the standard picture rather than proven strong causes on their own. Skin specialists at DermNet advise that when hair is shedding it is worth correcting any abnormality in thyroid function and in levels of iron, vitamin B12 and folic acid. Our vitamin B12 and folic acid guides explain where they fit in.
Vitamin C rarely causes hair loss on its own in the UK, but it helps your body absorb iron from food, so our vitamin C guide is worth a look if your iron is low. The reviews are consistent that correcting a real shortfall of these nutrients can help hair that was suffering because of it, while there is little evidence that taking more once your levels are already adequate does anything extra.
More is not better: nutrients that cause hair loss in excess
The most surprising point, and an important safety message for anyone tempted to megadose after self-diagnosing a deficiency, is that some nutrients cause hair loss when you take too much of them rather than too little. Reviews of diet and hair loss note that over-supplementation of vitamin A has a strong known link to hair loss, that selenium toxicity causes generalised hair loss, and that very high doses of vitamin E can also have an adverse effect on hair growth.
So it is worth reading our guides on vitamin A, selenium and vitamin E before taking any of them at high strength. Because 'hair, skin and nails' formulas stack several of these together, and people often take more than one product at once, the total can quietly climb into the range where it does harm rather than good. Do not exceed the safe upper limits, and treat a confirmed deficiency rather than supplementing blind.
Common myths, and what the evidence really says
Does calcium deficiency cause hair loss? This is a common search, and the honest answer is no, calcium deficiency is not a recognised cause of hair loss. Calcium is important for bones and teeth, but the reputable sources that list nutrients genuinely linked to hair loss, including the NHS and dermatology reviews, do not include calcium. If your hair is shedding, the far more likely nutritional culprit is iron, not calcium.
Isn't biotin the answer? Biotin (vitamin B7) is the headline ingredient in most hair supplements, but biotin deficiency is genuinely rare in people who eat a normal diet, and it is rarely the real cause of hair loss. There are no good trials showing that extra biotin helps hair in people who are not deficient. High-dose biotin also skews common blood tests, pushing results falsely high or low, so tell your doctor and the laboratory if you take it. Our biotin and hair loss guide has the detail.
What about protein? Protein is not a vitamin, but it is worth mentioning because severe protein shortage, for example from crash dieting or an eating disorder, can genuinely affect hair and tip it into shedding. A normal balanced diet supplies plenty, so this is only relevant at the extremes.
Brittle hair and nails: is it a deficiency?
Brittle, dry or easily broken hair alongside weak or ridged nails can accompany a genuine deficiency, iron in particular, which is classically linked to brittle and spoon-shaped nails as well as hair changes. It is not proof of one, though. Age, heat styling, bleaching, hard water and thyroid problems can all leave hair and nails brittle without any vitamin being to blame. The sensible move is not to guess but to get the underlying cause checked, because the fix is different for each.
How do I know? Get tested before you supplement
You cannot reliably tell a vitamin deficiency from your hair alone, because so many things cause the same diffuse shedding. The dependable route is a blood test through your GP. The tests worth asking about are ferritin and a full blood count for iron, vitamin D, vitamin B12 and folate, and thyroid function, which is one of the most common non-nutritional causes of shedding and is easy to miss. Treating what actually turns up is far more effective, and safer, than working through a shelf of supplements on a hunch.
The single idea to hold on to is this: correcting a proven deficiency can help hair that was suffering because of it, but taking supplements when your levels are already fine does not push growth any higher, and some can do harm in excess. If you want the detail on whether supplements are worth taking, see our guide on whether hair vitamins actually work. If your hair loss is persistent or patchy, or comes with other symptoms, see your GP, who can look for a real cause and point you to the options that have evidence behind them.
Frequently asked questions
Can a vitamin deficiency cause hair loss?
Yes. A genuine deficiency in certain nutrients can trigger hair to shed, usually as a diffuse thinning all over the scalp rather than a receding hairline, and correcting a real shortfall often lets the hair recover. That said, most hair loss is not caused by a vitamin deficiency, so it is worth getting the cause checked rather than assuming.
Which vitamin deficiency is the most common cause of hair loss?
Iron deficiency is the most common and most important, particularly in women, because heavy periods and pregnancy make it more likely. It is checked through ferritin, your iron stores, and a full blood count. Low vitamin D and zinc are the next most relevant.
Does calcium deficiency cause hair loss?
No. Calcium deficiency is not a recognised cause of hair loss. It matters for your bones and teeth, but the reputable sources that list nutrients genuinely linked to hair loss do not include calcium. If a nutrient is behind your shedding, iron is a far more likely candidate.
Can too much of a vitamin cause hair loss?
Yes. Too much vitamin A, selenium or vitamin E can all cause hair loss, so megadosing a multivitamin or stacking several hair supplements at once can backfire. More is not safer, which is one reason to correct a confirmed deficiency rather than supplement blind.
Can a deficiency cause brittle hair and nails?
It can. Brittle hair and weak or spoon-shaped nails can accompany iron deficiency in particular, but they can equally come from heat styling, bleaching, hard water or a thyroid problem. Because the treatment differs, it is best to have the cause checked rather than assume it is a vitamin.
How do I find out if a deficiency is causing my hair loss?
Ask your GP for a blood test. Useful checks include ferritin and a full blood count, vitamin D, vitamin B12 and folate, and thyroid function. Correcting a proven deficiency helps, whereas supplementing when your levels are already adequate does not, so testing first saves money and avoids the risk of taking too much.
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