Does vitamin D help hair growth? What the research does and doesn't show

No randomised trial we could cite shows that vitamin D supplements grow hair or stop hair loss. What exists is observational: a meta-analysis of 23 studies found people with non-scarring hair loss had lower blood vitamin D than healthy controls. That is an association; it does not show that raising vitamin D changes hair.

What the evidence doesn't support

• Vitamin D3 as a hair-growth or hair-loss aid. We found no randomised trial of vitamin D alone on hair to cite, so there is no result to report.
• Low vitamin D as the cause of hair loss. The meta-analysis compared levels between groups at one point in time. It cannot say whether low vitamin D contributes to hair loss, follows it, or both are caused by something else.
• A dose for hair. No trial gives one.
• Vitamin D3 with K2 for hair. No trial of the pair to cite.
• Vitamin D causing hair loss. We found no trial or review reporting it; see the question below.

What the studies found

Lower vitamin D in people with hair loss: an association

A 2024 systematic review and meta-analysis in the Journal of Cosmetic Dermatology pooled 23 studies of 3,374 people with non-scarring alopecia (including androgenetic alopecia, female pattern hair loss, alopecia areata and telogen effluvium) and 7,296 healthy controls. People with hair loss had lower serum 25-hydroxyvitamin D (weighted mean difference -7.29, 95% CI -9.21 to -5.38) and about three times the odds of vitamin D deficiency (odds ratio 3.11, 95% CI 2.29 to 4.22). Inconsistency between studies in the level result was very high (I2 95%). Certainty: the studies compared existing groups, so the result is an association and not evidence of cause or of benefit from supplementing. The authors suggested monitoring vitamin D status, which is a different step from saying a supplement regrows hair.

What a trial would need to show

To test whether vitamin D helps hair, people with hair loss would have to be randomly assigned to vitamin D or placebo and have hair measured over months. We did not find such a trial of vitamin D3 alone to cite, so this page makes no statement about the result. Larger trials in the general population, such as VITAL at 2,000 IU a day, did not report hair outcomes in the analyses we cite.

Question	Evidence we cite	Result
Do people with hair loss have lower vitamin D?	Meta-analysis, 23 studies, 10,670 people	Yes, on average (observational)
Does supplementing change hair?	No randomised trial cited	Unknown from what we cite

Questions people ask

Does vitamin D3 help with hair growth?

We found no randomised trial showing it does. People with hair loss have lower vitamin D levels on average, which is not the same as showing that a supplement regrows hair. Anyone wondering about a link should have a blood test, not guess.

Does vitamin D3 help with hair loss, or is it good for hair, or hair growth?

The same answer applies to all of these phrasings: no trial we can cite shows a benefit. The nutrient has defined roles in the body (NIH Office of Dietary Supplements: calcium and phosphorus absorption and normal bone), and we cite no hair role for it.

Can vitamin D3 deficiency cause hair loss?

The meta-analysis found deficiency more common in people with hair loss. It cannot say that deficiency caused it. Hair loss has many causes, and a clinician or dermatologist is the right person to work out which applies. See vitamin D deficiency: what the diagnosis means.

Does vitamin D3 cause hair loss?

None of the studies cited here reports it. A 2018 clinical review of vitamin D toxicity lists confusion, apathy, vomiting, abdominal pain, frequent urination, thirst and dehydration from high blood calcium, and does not list hair loss. If you notice shedding after starting a supplement, tell a clinician, as many things cause it and only an examination and tests can sort them out. See vitamin D side effects.

Is vitamin D3 and K2 good for hair, skin and nails?

We found no trial of the pair for hair to cite, and no claim is made for it. Vitamin K2 is a separate vitamin.

When to talk to a doctor

Sudden shedding, patchy bald spots, or thinning that is getting worse deserves a medical assessment, since hair loss can be a sign of other conditions and has treatments with evidence behind them. Vitamin D is not a treatment for hair loss, and nothing above supports using it in place of care. If you take medication or are pregnant or nursing, ask a doctor before adding a supplement.