Vitamin B7 (Biotin)

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By Nikola · Precision Nutrition L1 · Updated 5 November 2026

Biotin, or vitamin B7, is a water-soluble B vitamin that five enzymes need in order to process fats, glucose and amino acids. EFSA sets an adequate intake of 40 µg a day for adults and 45 µg when breastfeeding, and you get it from liver, eggs, fish, meat, seeds, nuts and sweet potato. Deficiency is rare in people eating a normal mixed diet. Biotin is sold mostly for hair and nails, where the evidence in healthy people is thin, and high-dose biotin can make some blood tests give wrong results.

What vitamin B7 does

Biotin is a cofactor for five carboxylase enzymes, including pyruvate carboxylase and the two forms of acetyl-CoA carboxylase. Together they work in the metabolism of fatty acids, glucose and amino acids. Biotin also has roles in histone modification, cell signalling and gene regulation (NIH ODS).

The EU allows seven health claims for foods that are at least a “source” of biotin (Regulation (EU) 432/2012):

• “Biotin contributes to normal energy-yielding metabolism”
• “Biotin contributes to normal macronutrient metabolism”
• “Biotin contributes to normal functioning of the nervous system”
• “Biotin contributes to normal psychological function”
• “Biotin contributes to the maintenance of normal hair”
• “Biotin contributes to the maintenance of normal skin”
• “Biotin contributes to the maintenance of normal mucous membranes”

The hair claim is the one on supplement packs. It means biotin is needed for normal hair; it does not show that extra biotin improves hair in someone who already gets enough.

How much you need a day

Group	EFSA adequate intake (AI)	EFSA upper limit (UL)	For reference: US AI (NIH)
Men	40 µg	Not set	30 µg
Women	40 µg	Not set	30 µg
Pregnancy	40 µg	Not set	30 µg
Breastfeeding	45 µg	Not set	35 µg
Children 4-10 years	25 µg	Not set	–

EFSA’s figures are adequate intakes based on what people in the EU eat without signs of deficiency; the extra 5 µg when breastfeeding replaces what passes into breast milk. There is no upper limit: EFSA’s overview of upper levels lists biotin as “no adequate data to derive a UL” (Scientific Committee on Food, 2001), and the US Food and Nutrition Board found no evidence in humans that biotin is toxic at high intakes. The amounts are tiny: 40 µg is 0.04 mg.

Best food sources

Food	Portion	Biotin per portion	Share of EFSA AI (40 µg)
Beef liver, cooked	85 g (3 oz)	30.8 µg	77%
Egg, whole, cooked	1 egg	10.0 µg	25%
Pink salmon, canned in water	85 g (3 oz)	5.0 µg	13%
Pork chop, cooked	85 g (3 oz)	3.8 µg	10%
Sunflower seeds, roasted	¼ cup	2.6 µg	7%
Sweet potato, cooked	½ cup	2.4 µg	6%
Almonds, roasted	¼ cup	1.5 µg	4%
Tuna, canned in water	85 g (3 oz)	0.6 µg	2%
Spinach, boiled	½ cup	0.5 µg	1%
Broccoli, fresh	½ cup	0.4 µg	1%

Source: NIH Office of Dietary Supplements, Biotin fact sheet, table of selected food sources, checked 5 November 2026. USDA FoodData Central’s SR Legacy records, which we use for the other vitamins, do not report biotin (checked for hard-boiled egg, FDC 173424), so this table gives the NIH values per serving only, in NIH’s portions. The share of the EFSA adequate intake is calculated and rounded.

The practical answer is eggs. One cooked egg covers about a quarter of the day, and a mixed diet with fish such as salmon, some meat, sunflower seeds, almonds and sweet potato fills in the rest. Spinach, broccoli and canned tuna add very little. Cook your eggs: raw egg white contains avidin, a protein that binds biotin tightly and stops it being absorbed, and cooking breaks avidin down. For ideas, see 7 healthy foods to eat for breakfast or a chickpea and sweet potato curry.

Deficiency: signs and who is at risk

Biotin deficiency is rare, and severe deficiency in healthy people eating a normal mixed diet has never been reported (NIH). When it does happen, the signs are thinning hair that can progress to losing all body hair, a scaly red rash around the eyes, nose and mouth, conjunctivitis, brittle nails and, in adults, depression, lethargy, hallucinations and tingling or pins and needles (paresthesias).

• Biotinidase deficiency. A rare inherited (autosomal recessive) disorder. In the US all newborns are screened for it.
• Chronic alcohol use. Plasma biotin is low in about 15% of people with chronic alcoholism.
• Pregnancy and breastfeeding. At least a third of pregnant women develop marginal biotin deficiency despite normal intakes. What this means for health is not yet clear, and NIH says more research is needed.

Supplements: when they make sense

If you have diagnosed deficiency or biotinidase deficiency, biotin is treatment your doctor will set. For hair and nails in healthy people, be realistic. NIH describes the claims as “supported, at best, by only a few case reports and small studies.” The nail studies were small and had no placebo group, and for hair there are only case reports in children with a rare condition (uncombable hair syndrome). A 2017 review (Patel and colleagues) found 18 published cases where biotin helped hair or nails, and every one of them had an underlying problem such as biotin deficiency, brittle nail syndrome or uncombable hair. The authors concluded there is not enough evidence to support biotin supplements in healthy people.

That matters because of dose. The FDA reports many supplements with 20 mg of biotin and some with up to 100 mg per pill; some hair, skin and nail products contain up to 650 times the recommended daily intake. Studies have found no adverse effects at 10-50 mg a day and no toxicity at up to 200 mg a day, and the NHS says 0.9 mg or less a day from supplements is unlikely to cause harm. The real risk is not toxicity but lab tests.

Food first: if your hair or nails have changed, a doctor can look for the common causes. We do not recommend specific products on this page.

Who should be careful

• Anyone having a blood test. Many lab tests use a biotin-streptavidin method, and high biotin intake can make the result falsely high or falsely low, depending on the test. NIH lists thyroid hormone and 25-hydroxyvitamin D tests among those affected and describes patients on 10-300 mg a day wrongly appearing to have Graves’ disease. A single 10 mg dose interfered with thyroid tests taken within 24 hours.
• Heart tests. Biotin can cause a falsely low troponin result, the test used to diagnose a heart attack, which can lead to a missed diagnosis. NIH reports, citing the FDA, that a patient with a high intake of supplemental biotin died after a troponin test that came back falsely low. The FDA first warned about biotin and lab tests in November 2017 and updated the warning in November 2019.
• What to do. The FDA advises telling your doctor if you take biotin or plan to, remembering that multivitamins, including prenatal ones, can contain it, and checking labels, because high doses are not always clear from the product name. It also says there is not enough information to know whether stopping biotin for a set number of hours before a test prevents wrong results.
• High-dose prescriptions. Doctors sometimes recommend up to 300 mg a day for conditions such as multiple sclerosis (FDA), so lab results need to be read with that in mind.
• Epilepsy medicines. Long-term use of carbamazepine, primidone, phenytoin or phenobarbital is linked to lower biotin levels, probably because these drugs speed up its breakdown.

FAQ

Does biotin help hair growth?

The evidence supports it only when hair problems come from low biotin or a rare condition that responds to it. A 2017 review found that all published cases of benefit involved an underlying problem, and the authors found no good evidence for biotin supplements in healthy people. The EU claim that biotin “contributes to the maintenance of normal hair” means you need enough of it, not that more grows more hair.

How much biotin do I need a day?

EFSA’s adequate intake is 40 µg a day for adults, including in pregnancy, and 45 µg when breastfeeding. One cooked egg gives about 10 µg, a quarter of that. The FDA reports many supplements with 20 mg (20,000 µg) per pill, 500 times that amount.

Should I stop taking biotin before a blood test?

Tell your doctor and the lab that you take it, ideally before the test. High-dose biotin can make thyroid, vitamin D, hormone and troponin results falsely high or low. The FDA says there is not enough information to know whether stopping for a set number of hours prevents wrong results, so how to handle it is a decision for your doctor.

Related entries and articles

• Eggs – the easiest everyday source
• Salmon and canned tuna
• Sunflower seeds and almonds
• Sweet potato, spinach and broccoli
• Vitamin B5 (pantothenic acid) and vitamin B6
• Vitamin B12
• 7 healthy foods to eat for breakfast
• Chickpea and sweet potato curry

Sources

1. NIH Office of Dietary Supplements: Biotin, Fact Sheet for Health Professionals. ods.od.nih.gov
2. EFSA NDA Panel (2014). Scientific Opinion on Dietary Reference Values for biotin. EFSA Journal 3580. efsa.europa.eu
3. EFSA: Overview on Tolerable Upper Intake Levels, version 11, August 2025. efsa.europa.eu
4. Commission Regulation (EU) No 432/2012 – permitted health claims. legislation.gov.uk
5. NHS: Vitamin B (biotin). nhs.uk
6. U.S. Food and Drug Administration: UPDATE: The FDA Warns that Biotin May Interfere with Lab Tests, FDA Safety Communication, 5 November 2019 (original 28 November 2017), as reproduced by Drugs.com. drugs.com
7. U.S. Food and Drug Administration: Biotin Interference with Troponin Lab Tests – Assays Subject to Biotin Interference, content current as of 21 June 2022. fda.gov
8. Patel DP, Swink SM, Castelo-Soccio L (2017). A Review of the Use of Biotin for Hair Loss. Skin Appendage Disorders 3(3):166-169. ebi.ac.uk (Europe PMC)
9. USDA FoodData Central, SR Legacy: Egg, whole, cooked, hard-boiled (FDC 173424) – checked for biotin, none reported. fdc.nal.usda.gov

This page is for information only and is not medical or dietary advice.