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Biotin

A water-soluble B vitamin, bought above all for hair, skin and nails.

People take it for
  • Hair growth
  • Nails
  • Blood sugar
  • Skin

A plain-English overview, not advice. Written from published reviews and trials and from what people say in public forums.

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What is biotin?

Biotin, also called vitamin B7, is a water-soluble B vitamin that the body puts to work as a helper for a small group of enzymes: the ones that build fatty acids, break down certain amino acids, and make glucose when none is arriving from food. The amount usually named as a day’s intake for an adult is about 30 micrograms, and a little of it sits in most multivitamins. Outright, symptomatic shortage is described as rare. It is also sold on its own, in tablets carrying doses many times larger than that daily figure.

Why do people take biotin?

Hair

The thinking. Hair is what most people are buying biotin for; it is the vitamin’s whole commercial reputation, and reviews describe that popularity plainly, as a supplement sold widely for hair and nail growth. The idea rests on two things. One is biotin’s day job, helping the enzymes that build fatty acids and break down amino acids, in tissue that grows without stopping. The other is what is described where biotin is genuinely lacking, from an inherited enzyme fault or an acquired shortage, with poor hair growth among the things noted.

What research has found. No trial in people has measured this, so there is nothing to report either way yet.

Nails

The thinking. Nails are the second of the three things biotin is bought for, and the only one of them with a trial behind it. Splitting, flaking nails are a common enough complaint, and the thinking is that a vitamin whose job is helping to build fatty acids and handle amino acids matters to tissue that has to grow continuously.

What research has found. One randomised trial gave fifty adults with brittle nails, average age 64, a nail lacquer for four months, and added 10 mg of biotin a day for about half of them. Severity scores fell by a similar amount in both groups, 57 and 62 per cent, though more of those on biotin reached a halving of their score. Few studies have measured this yet, so there is little to go on either way.

Blood sugar and blood fats

The thinking. Biotin has a hand in two things the body does with sugar and fat: making glucose when none is coming in from food, and building fatty acids. That is the thinking behind taking it with blood sugar in mind, and it is why researchers have measured what a supplement does to the numbers on a blood test.

What research has found. A review pooled five randomised trials, 445 adults with type 2 diabetes between them, taking biotin for four weeks to three months: average fasting blood glucose, total cholesterol and triglycerides came out lower, insulin was no different, and for HbA1c the reviewers judged there was too little to go on. A separate month-long trial, in adults with and without diabetes, found lower triglycerides and lower VLDL, one of the particles that carry fat around the blood, while cholesterol, glucose and insulin were unchanged. Studies here point in different directions, so this one is still being worked out; the dose, how long people took it and who took part all seem to matter.

Skin

The thinking. Skin is the third part of the familiar trio, and people reach for biotin for it in the same breath as hair and nails; supplements for skin, hair and nail complaints are a familiar part of what skin specialists are asked about. The thinking runs from the other end. Reviews describe inflammation of the skin where biotin is lacking, whether through the diet or through an inherited fault in the enzymes that fasten biotin onto proteins, and describe biotin acting on the chemistry of inflammation by a separate route as well.

What research has found. Nobody has tested this in a trial yet, so there is nothing to report either way.

What does biotin do in the body?

Biotin is a helper rather than a fuel. The body clips it onto a small group of enzymes called carboxylases, and those enzymes then get on with some of the most everyday chemistry there is: building fatty acids, breaking down certain amino acids from protein, and making glucose when none is arriving from food. It dissolves in water, is taken up readily, and leaves again quickly in the urine.

Biotin is also fastened onto proteins that are not carboxylases, and reviews describe a hand for it in how genes are read and in the chemistry of inflammation, which is one reason a shortage shows itself in the skin as well as in hair and nails. Very little is needed. Against a daily figure of roughly 30 micrograms, the supplements sold for hair and nails are measured in milligrams, and the high-dose research used more again.

What do people say about taking biotin?

These are anecdotes people have shared, not evidence.

What people like

  • Four of the six threads read come from one parenting forum, so most of the voices here are women taking biotin for their hair.
  • Nails come up as the clearest change people notice, sometimes while they are still unsure whether their hair has done anything at all.
  • Where people do report a change to their hair, they describe thickness and condition rather than length, usually after two to five months.
  • Several describe it as slow going: months rather than weeks before anything is visible, which some found longer than they had expected.

Common complaints

  • Several say it did nothing whatever for them, two months or more of daily tablets with no change to either hair or nails.
  • Skin breakouts are the side effect raised most often, both by people who had them and by people warning others off it.
  • Not everyone in the threads agrees about the skin: one person taking it for months reported no trouble with theirs at all.
  • Doubt runs through the threads themselves: people question the price and the hype, and one poster’s dermatologist suggested iron and folic acid instead.

How people take it

  • Doses are rarely named. People say tablets, gummies or a combined hair supplement far more often than they say how much they take.
  • Gummies and combined hair supplements come up about as often as plain biotin tablets, and a couple of people take two a day.
  • Iron is the thing most often taken alongside it, whether inside a multivitamin, inside a combined supplement, or suggested in its place.
  • People commonly pair it with something they put on their hair or nails, so few of them are judging biotin on its own.
  • Some stop after a couple of months when nothing has changed, and a few describe giving up on hair supplements altogether.

Read from these public discussions:

What forms of biotin are there?

Form What’s different Per serving, on products we list
Biotin Biotin itself: the only form sold, written on some labels as d-biotin. 500 µg to 10 mg

What else is worth knowing about biotin?

  • High doses of biotin can distort common laboratory blood tests. The vitamin is part of the chemistry many test kits are built around, so a result can come back falsely high or falsely low; thyroid and reproductive hormone tests, cardiac tests and immunosuppressant drug levels are among those most at risk.
  • In one published case a person’s thyroid results were markedly abnormal and did not match how the person actually was, and they settled as soon as the biotin stopped. Amounts from food do not usually reach the level at which this happens, and reviews note that people often do not realise they are taking biotin at all.
  • The amounts used in research run from 10 mg a day in the nail trial to 300 mg a day of pharmaceutical-grade biotin in the multiple sclerosis trials, against a daily intake for an adult of about 30 micrograms. Labels give the amount per serving, and a serving may be more than one capsule.
  • In the largest of those high-dose trials, in 642 adults with progressive multiple sclerosis, side effects were reported about as often on biotin as on placebo, and there was no difference between the groups in disability or walking speed.

If you take medication, are pregnant, or have a health condition, check with a pharmacist or GP first.

The research behind this page (9 studies)
  1. Treatment of brittle nail with a hydroxypropyl chitosan-based lacquer, alone or in combination with oral biotin: A randomized, assessor-blinded trial. (2019, randomised trial)
  2. Influence of biotin intervention on glycemic control and lipid profile in patients with type 2 diabetes mellitus: A systematic review and meta-analysis. (2022, systematic review)
  3. Biotin supplementation reduces plasma triacylglycerol and VLDL in type 2 diabetic patients and in nondiabetic subjects with hypertriglyceridemia. (2006, randomised trial)
  4. A Review of the Use of Biotin for Hair Loss. (2017, review)
  5. Biotin: From Nutrition to Therapeutics. (2017, review)
  6. Regulation of immunological and inflammatory functions by biotin. (2015, review)
  7. Dietary supplements in dermatology: A review of the evidence for zinc, biotin, vitamin D, nicotinamide, and Polypodium. (2021, review)
  8. Pharmacokinetics and pharmacodynamics of MD1003 (high-dose biotin) in the treatment of progressive multiple sclerosis. (2016, review)
  9. Best practices in mitigating the risk of biotin interference with laboratory testing. (2019, review)

How much does biotin cost?

That depends on the form and the pack, so we work out the price of the same dose of every biotin product we can find and rank them.

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