Does biotin make hair grow?

This question usually gets answered with a shrug about how the evidence is mixed. It does not need one. A regulator wrote its answer down.

The topical version

There is a US regulation covering over-the-counter products sold for external use as hair growers or for hair loss prevention. It lists what has been marketed for that purpose, and biotin is on the list by name, alongside “all other B-vitamins”.

Its conclusion: “all labeling claims for OTC hair grower and hair loss prevention drug products for external use are either false, misleading, or unsupported by scientific data”.

That covers biotin shampoos and biotin serums sold on a growth claim. It has been in force for decades and it has not been softened.

The oral version

Not covered by that regulation, and the answer is less blunt but goes the same way.

Biotin deficiency causes hair loss, and correcting it reverses that. So in someone who is genuinely deficient, biotin works, in the way that any deficiency correction works.

Deficiency is rare. It arises from specific genetic conditions, prolonged intravenous feeding, some anticonvulsants, or eating a lot of raw egg white. The NHS is blunt about the baseline: biotin “is needed in very small amounts”, and “the bacteria that live naturally in your bowel are able to make biotin, so it’s not clear if you need any additional biotin from the diet”.

If it is not clear you need any, taking a large amount is unlikely to be the thing that was missing.

The reason to be careful anyway

High-dose biotin interferes with common blood tests, including thyroid function tests. The 2026 European Thyroid Association guideline records that biotin has “been described to cause falsely high or low hormone results in streptavidin-biotin-based assays”.

That can produce a thyroid result that looks like disease in someone whose thyroid is fine, and the investigations that follow are real even though the abnormality is not. The full account is on Biotin.

So the honest summary is not “harmless but useless”. It is that a supplement with little to show for itself carries a specific, avoidable consequence, and the way to avoid it is to tell whoever takes your blood that you take it.

What does have evidence

Minoxidil is the one thing on that shelf that went through drug approval, in 1996, and it has an approved indication rather than a claim.

Deficiencies that actually cause hair loss are worth finding rather than guessing at, iron in particular. That is a blood test, and it is a better use of the same money than a formula built on assuming the answer.

And the most treatable common cause of hair loss has no product attached to it at all: traction alopecia is mechanical, caused by sustained pull, largely preventable and largely reversible when caught early. That is covered on the hair loss page.