Quick answer

Biotin is a B vitamin your body uses to turn carbohydrates, fats and protein into energy. Adults need about 30 mcg a day, and most people get that from food. Biotin is sold for hair, skin and nails, but NIH says the evidence for those uses is thin, and high doses can skew some lab tests.^1,2,3

Key facts

Adults need 30 mcg of biotin a day, and 35 mcg while breastfeeding.²
Typical western diets supply about 35 to 70 mcg a day, so a true shortage is rare.²
The hair, skin and nail evidence is limited to case reports and a few small studies with no placebo group.^2,4
Biotin above the recommended intake can make some lab tests, including thyroid and troponin tests, read falsely high or falsely low.^2,3
No upper limit is set, and studies giving 10 to 50 mg a day found no adverse effects.²

What biotin is

Biotin, also known as vitamin B7, is a water-soluble B vitamin found in many foods and sold as a supplement.^2,3

Inside cells, biotin is attached to five enzymes called carboxylases. Each carries out a key step in using fats, sugars or amino acids, which puts biotin close to the center of how the body turns food into usable energy. Biotin also has roles in gene regulation and in the signals cells send each other.²

People in western countries typically get about 35 to 70 mcg of biotin a day from food, more than the 30 mcg adults need.²

Running low on biotin is rare. A severe shortage has never been reported in healthy people eating a normal mixed diet.²

What the evidence shows

Each claim carries a grade, with the amount behind it. Only one claim meets our standard for biotin, and it is a basic nutrient role rather than a result from supplement trials: it describes what getting enough does, not what extra adds.⁵

Helps the body turn the carbohydrates, fats and protein in food into energy*^1,2,5,6

Moderate evidence

A long-established role of the vitamin rather than a finding from supplement trials. NIH describes biotin as a helper for five enzymes that carry out key steps in using fats, sugars and amino acids, and the EU list of permitted nutrient-function statements includes energy-yielding metabolism for the B vitamins. Most people get enough biotin from food, and the Institute of Medicine found no observable benefit from B vitamin intakes beyond those that avoid the signs of running short.

Amount studied: Adequate intake: 30 mcg a day for adults, 35 mcg while breastfeeding, from food and supplements together

Hair, skin and nails

Thinning hair, skin rashes and brittle nails are signs of a true biotin shortage, which is why supplements are marketed for hair, skin and nails. NIH says those claims rest, at best, on a few case reports and small studies.^1,2

For hair, the only reports are case reports in a few children with a rare inherited hair-shaft condition, who took 3 to 5 mg a day for 3 to 4 months. A review of 18 published cases found that everyone whose hair or nails changed on biotin had an underlying cause for poor growth, and found too little evidence to recommend biotin to healthy people.^2,4

For nails, three small studies without a placebo group gave 2.5 mg a day to people with brittle, splitting or soft nails. In one, 41 of 45 people had firmer, harder nails after about 5.5 months; in another, 22 of 35 were judged better after 6 to 15 months. None checked whether people were low in biotin to begin with.²

For skin, the evidence is limited to a few case reports in infants.²

None of this shows a change in hair, skin or nails in people who already get enough biotin, and that describes most buyers, because a true shortage is rare. For that reason we make no hair, skin or nail claim for biotin.^2,4

NIH says more research is needed to know whether biotin supplements make any difference to hair, nails or skin, especially in healthy people.^1,2

How much you need

Adults need 30 mcg of biotin a day, the same amount during pregnancy, and 35 mcg while breastfeeding. These are adequate intakes, set because there was not enough evidence for a recommended dietary allowance.^1,2

The Daily Value for biotin is 30 mcg, so a 5,000 mcg supplement provides about 167 times the Daily Value.²

Many biotin supplements contain hundreds of times the daily need. A dose of 10 mg (10,000 mcg) a day, which researchers describe as common in over-the-counter products, is more than 300 times the adequate intake. The dosage guide sets out the amounts by age and what studies used.^2,7

Food sources

Organ meats, eggs, fish, meat, seeds, nuts and certain vegetables such as sweet potatoes are the richest food sources of biotin.^1,2

A whole cooked egg covers about a third of the Daily Value, and 3 ounces of cooked beef liver covers all of it.²

Raw egg white contains avidin, a protein that binds biotin tightly and stops it from being absorbed. Cooking breaks avidin down, so cooked eggs do not have this effect.²

Biotin in supplements

Biotin is sold on its own, in B-complex supplements and in many multivitamins, including prenatal vitamins, and in products marketed for hair, skin and nails.^1,3

Supplements contain free biotin, which the body absorbs almost completely, even at 20 mg a day.²

Because biotin turns up in so many products, it is easy to take it from two or three sources at once without noticing. Adding up the biotin on each Supplement Facts panel is the only way to know your total.^1,3

What's in ours

What’s in ours

Men's Multi: Biotin, 300 mcg per serving, from the label

Lab tests, medicines, and who should ask first

Biotin above the recommended intake can make some lab tests read falsely high or falsely low, depending on how the test is built. Wrong results can lead to the wrong treatment or to a missed or mistaken diagnosis.^2,3

FDA has reported that a patient taking high-dose biotin died after a troponin test, used to help diagnose a heart attack, gave a falsely low result. FDA continues to receive reports of falsely low troponin results caused by biotin.^2,8

No upper limit has been set for biotin, because there is no evidence in humans that it is toxic at high intakes. Studies giving 10 to 50 mg a day found no adverse effects, and people with a rare inherited condition that affects biotin have taken up to 200 mg a day by mouth without signs of toxicity. The main known risk of high intakes is wrong lab test results.^2,9

Ask your pharmacist or doctor first

Biotin can distort the thyroid blood tests used to check and adjust a levothyroxine dose. The levothyroxine label says biotin supplements interfere with thyroid hormone tests built on biotin and streptavidin, which may give wrong results, and tells patients to stop biotin and biotin-containing supplements for a time before thyroid testing.^2,10

On the medicine's label

Your doctor may want to check on you

In a study of 264 people with epilepsy, taking anticonvulsants such as carbamazepine, phenytoin, phenobarbital or primidone for a year or more was linked to lower biotin levels. These medicines may speed up the breakdown of biotin and reduce its absorption.^1,2

Reported in studies

Tell your doctor and the lab that you take biotin before any blood test, especially thyroid, hormone or heart tests³
Ask first if you take levothyroxine or another thyroid medicine, or an anticonvulsant
Ask first if you are pregnant or breastfeeding
Count the biotin in any multivitamin, B complex or hair, skin and nail product you already take¹

Questions people ask

Does biotin make hair grow?

There is no good evidence that it does in people who get enough biotin. The only hair reports are case reports in a few children with a rare inherited hair problem, and a review of 18 published cases found that everyone who responded had an underlying cause for poor hair or nail growth.^2,4

Is biotin the same as vitamin B7?

Yes. Biotin is also called vitamin B7. It is one of the B vitamins and dissolves in water.^2,3

Can biotin mess up blood tests?

Yes. Biotin above the recommended intake can make tests that use biotin read falsely high or falsely low, including thyroid tests and troponin tests used to diagnose a heart attack. Tell your doctor and the lab that you take it, and ask whether to pause it before the test.^2,3

Is 10,000 mcg of biotin too much?

No upper limit is set, and studies giving 10 to 50 mg a day found no adverse effects. But in six healthy adults, 10 mg (10,000 mcg) a day for a week gave wrong results on 9 of 23 lab tests that use biotin, so tell your doctor and the lab if you take that much.^2,7

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Sources

*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.