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Biotin
A B vitamin found in foods such as eggs, organ meats, fish, nuts and seeds, and often promoted in supplements for hair, skin and nail health.
Explained simply · Last reviewed
What it is
Biotin is a B vitamin, also known as vitamin B7, found naturally in some foods and sold as a dietary supplement. The Office of Dietary Supplements (ODS), part of the US National Institutes of Health, names organ meats, eggs, fish, meat, seeds, nuts and some vegetables, such as sweet potatoes, as the foods with the most biotin. Because hair loss, skin rashes and brittle nails are signs of biotin deficiency, it says, biotin supplements are often promoted for hair, skin and nail health.
More about Biotin
The Office of Dietary Supplements (ODS), part of the US National Institutes of Health, names organ meats, eggs, fish, meat, seeds, nuts and some vegetables, such as sweet potatoes, as the foods with the most biotin. Because hair loss, skin rashes and brittle nails are signs of biotin deficiency, it says, biotin supplements are often promoted for hair, skin and nail health.
A 2024 review in a dermatology journal notes biotin's older name, vitamin H, from the German words for hair and skin, "Haar und Haut". ODS explains that biotin is a helper (cofactor) for five enzymes involved in the metabolism of fatty acids, glucose and amino acids.
ODS says biotin deficiency is rare, and that severe deficiency has never been reported in healthy people eating a normal mixed diet. It names groups more likely to run low, listed under how to take it. Biotin is sold on its own, in B-complex supplements and in some multivitamins, according to ODS.
The US Food and Drug Administration (FDA) adds that biotin is often found in multivitamins, prenatal vitamins and supplements marketed for hair, skin and nail growth. It warns that in people who consume more than the recommended daily intake, biotin can cause falsely high or falsely low results in some laboratory tests, which the safety section covers.
The reviews cited below also describe trials of biotin, sometimes combined with chromium, for blood sugar in type 2 diabetes, and of a high-dose biotin product in progressive multiple sclerosis. The claims report what ODS and those reviews found.
Also known as: vitamin B7, vitamin H
At a glance
Safety: known risks, 2 groups who should avoid it or take extra care and 2 documented interactions. See Safety ↓Claims made about Biotin, and how strong the evidence is for each:
- Improves hair growth or reduces hair lossEvidence rating: Insufficient
- Strengthens brittle or splitting nailsEvidence rating: Insufficient
- Improves skin healthEvidence rating: Insufficient
- Lowers blood sugar in people with type 2 diabetesEvidence rating: Limited
- Slows or reverses disability in progressive multiple sclerosis, at high dosesEvidence rating: Insufficient
Each rating follows our published rules and the sources cited for it. We don’t add our own medical judgment. How we rate
Safety
Read this before the ratings below.
Risks
- ODS warns that high biotin intakes, and potentially even intakes above the Adequate Intake, may cause clinically significant falsely high or falsely low laboratory test results, depending on the test. It says these incorrect results may lead to inappropriate patient management or misdiagnosis of a medical condition. ODS also reports that no upper limit has been set, because there is no evidence in humans that biotin is toxic at high intakes.
- ODS describes case reports in which biotin made test results falsely suggest Graves' disease and severe hyperthyroidism, including in children given high doses for inherited metabolic diseases. It also reports that, according to FDA, a person with a high intake of supplemental biotin died after a troponin test, used to help diagnose a heart attack, gave a falsely low result because the test was subject to biotin interference.
- The US Food and Drug Administration (FDA) states, in its 2020 guidance on testing for biotin interference, that biotin levels in people who consume more than the recommended daily intake can cause falsely high or falsely low results, depending on how the test works. It names hormone tests and tests for markers of heart health such as troponin, and states that warnings in the test makers' labeling alone may not be enough to reduce the risk of incorrect results in all cases.
Who should avoid it or take extra care
- People who take supplements containing biotin and are having laboratory tests: ODS reports that FDA advises health care providers to ask their patients about any supplements containing biotin, and to consider biotin interference as a possible source of error when laboratory results do not match how the patient presents.
- ODS advises that people who take anticonvulsants or other medications regularly should discuss their biotin status with their health care providers.
Documented interactions
- Laboratory tests that use biotin-streptavidin technology, such as some thyroid hormone, troponin and 25-hydroxyvitamin D tests: ODS reports that very high biotin intakes may interfere with these tests and produce falsely normal or abnormal results. It cites a small study in six healthy adults who took supplemental biotin for a week, which found falsely low results for thyroid stimulating hormone, which could lead to a wrong diagnosis of an overactive thyroid, and for NT-proBNP, which could mean heart failure is missed. FDA states that biotin can cause falsely high or falsely low results depending on how the test works. Source [1]Source [2]
- Anticonvulsants: carbamazepine (Tegretol, Carbatrol, Epitol, Equetro), primidone (Mysoline), phenytoin (Dilantin, Phenytek) and phenobarbital (Luminal, Solfoton): ODS reports that in a study of 264 people with epilepsy, at least a year of anticonvulsant treatment was associated with significantly lower blood biotin levels than in a control group, and that a few smaller studies found similar results. It suggests the reason could be that these medicines speed up the breakdown of biotin and reduce its absorption. Source [1]
Safety sources: Source [1]Source [2]
What the evidence says
Each claim is rated on its own evidence. Ratings follow the scale on our methodology page.
Improves hair growth or reduces hair loss Evidence rating: Insufficient
People take it hoping it will make their hair grow thicker and stop it falling out.
ODS says only case reports in children with a rare hair disorder support it, and the one placebo-controlled trial a 2024 review found showed no difference in hair growth.
ODS, the US Office of Dietary Supplements, explains that hair loss is a sign of biotin deficiency, which is why biotin supplements are often promoted for hair. It says these claims are supported, at best, by only a few case reports and small studies. For hair, it reports only case reports, all in children. In children with uncombable hair syndrome, a rare disorder of the hair shaft, biotin significantly improved hair health after three to four months. ODS says future studies are needed, especially among healthy people.
A 2024 review searched one database, PubMed, for studies of biotin alone for hair growth or quality, and found three. The only double-blind, placebo-controlled one dates from 1966. It gave biotin or a placebo to 46 women with diffuse hair loss for four weeks. Both groups improved, with no significant difference in hair growth between them. The other two studies, in people taking the acne drug isotretinoin and in women after weight-loss surgery, were not blinded. The reviewers write that neither "had striking results in favor of biotin".
The reviewers conclude: "The utility of biotin as a hair supplement is not supported by high-quality studies." They add that no study has shown biotin to benefit hair growth in healthy people. Their review limited itself to articles available through the authors' own library and its methods describe no formal appraisal of study quality. Under this site's rules that makes it a narrative review, so it does not count toward the rating.
This page rates the claim on the ODS statement. Under this site's rules, an insufficient rating means the cited evidence is too limited to show whether there is an effect. It does not mean the sources found no effect.
Sources: Source [1]Source [2]
Strengthens brittle or splitting nails Evidence rating: Insufficient
People with brittle nails take it hoping their nails will grow stronger and split less.
ODS says the evidence is three small studies with no placebo group that did not report participants' biotin levels, and that more research is needed.
ODS reports that brittle nails are a sign of biotin deficiency. It describes the evidence on biotin for brittle nails as three small studies that did not include a placebo group. None reported the participants' biotin status before they started.
ODS describes each. In the first, nail thickness rose by 25% in eight people whose nails were sampled just before and after taking biotin. In 14 others sampled at different times, thickness rose by 7%, a difference that was not statistically significant. In the second, 41 of 45 people with thin, brittle fingernails (91%) had firmer, harder nails after an average of five and a half months. The third, which looked back at records of 35 people, found clinical improvement in 22 of them (63%).
ODS says future studies are needed to find out whether biotin supplements might improve nail health, especially in healthy people. This page rates the claim insufficient on that statement.
Sources: Source [1]
Improves skin health Evidence rating: Insufficient
People take it hoping for clearer, healthier skin.
ODS says the evidence is limited to a small number of case reports, all in infants, and that more research is needed.
ODS reports that skin rashes are a sign of biotin deficiency, and that biotin supplements are often promoted for skin health. It describes the evidence as limited to a small number of case reports, all in infants. ODS says those reports showed "dramatic improvements" in rash or dermatitis, and in hair loss, after biotin.
ODS says future studies are needed to find out whether biotin supplements might improve skin health, especially in healthy people. No cited source reports a trial of biotin for skin in adults. This page rates the claim insufficient on the ODS statement.
Sources: Source [1]
Lowers blood sugar in people with type 2 diabetes Evidence rating: Limited
People with type 2 diabetes take it hoping it will bring their blood sugar down.
Five small, short trials showed no statistically significant fall in fasting glucose, says a 2025 overview, which calls the evidence low quality though its chart rates it higher.
This claim is about laboratory measures of blood sugar: fasting glucose, HbA1c and insulin. A 2022 review pooled five placebo-controlled trials in 445 adults with type 2 diabetes. They ran between 1993 and 2007 in the United States, Mexico and Japan, and lasted four weeks to three months. Two of the five, including the largest with 348 people, gave biotin combined with chromium picolinate. The three trials of biotin alone had 61 people between them. The reviewers report that, in their subgroup analysis, trials with and without chromium did not differ significantly.
The review's text describes the fall in fasting glucose as significant. Its forest plot gives an average difference of −1.21 mmol/L (95% CI −2.73 to 0.31; p = 0.12), a range that includes no change. The text reports no differences between trials for this outcome, but the plot shows their results varied widely (I² = 91%). The reviewers also report a larger fall in the two higher-dose trials; the plot's range for those two also includes no change.
Only one trial measured HbA1c, too few to pool, and insulin did not differ significantly. The reviewers conclude that biotin "may decrease FBG". They note that no trial lasted longer than three months and that none reported participants' biotin levels.
A 2025 overview of 14 reviews of water-soluble vitamins in type 2 diabetes found that 2022 review to be the only one on biotin. It states that biotin "had no statistically significant effect on FBG", and that it found no significant effect on blood sugar control or insulin resistance. It suggests this may be because only that one review, of just five trials with a small pooled sample, has studied biotin. Its text says its quality ratings, by AMSTAR-2 and GRADE, "revealed low quality" in the biotin review.
The overview's summary chart, however, rates how sure it is of the biotin results (certainty) as high for fasting glucose and moderate for HbA1c and insulin. This page reports both and does not settle which is right. It rates the claim limited, below the chart's moderate certainty, because the overview's authors describe the biotin evidence as low quality and the 2022 review's pooled glucose result includes no change.
Sources: Source [1]Source [2]
Slows or reverses disability in progressive multiple sclerosis, at high doses Evidence rating: Insufficient
People with progressive multiple sclerosis take high-dose biotin hoping it will slow or reverse their disability.
A 2020 Cochrane review concluded the evidence is insufficient; it found one small, maker-funded trial of high-dose biotin and listed a larger trial as still under way.
A 2020 Cochrane review of diet and supplements in multiple sclerosis included one trial of biotin. It enrolled 154 people with primary or secondary progressive multiple sclerosis in France. They took a high-dose biotin product, MD1003, or a placebo for 12 months. On the trial's measure of improved disability, 13 people on biotin and none on placebo improved at nine months, confirmed at 12. Scores on the disability scale (EDSS) improved more with biotin.
The trial found no significant difference in the change in time to walk 25 feet, in new lesions on brain scans in those scanned, or in fatigue, and no consistent difference in quality of life. Relapses occurred in 5 of 103 people on biotin and 4 of 51 on placebo. Six people on biotin and seven on placebo stopped because of side effects. One serious adverse event, a rash affecting the skin and mucous membranes, and one death by suicide were both in the biotin group. The Cochrane reviewers note the trial was funded by MedDay Pharmaceuticals, which makes MD1003. They did not rate their certainty in this trial's results.
The reviewers write that there was limited evidence to assess any single supplement, and that high-dose biotin "has shown promise in a small study". They conclude that there is "insufficient evidence to determine whether supplementation with antioxidants or other dietary interventions have any impact on MS-related outcomes".
Their search ran to May 2019. They list a larger placebo-controlled trial of high-dose biotin in progressive multiple sclerosis as ongoing at that time. No review cited on this page includes that larger trial's results. This page rates the claim insufficient on the Cochrane conclusion.
Sources: Source [1]
How and when to take it
What the cited sources say about taking it. Ask your doctor or pharmacist what applies to you.
No RDA or upper limit has been set
ODS reports that the Food and Nutrition Board found the data insufficient to set an Estimated Average Requirement or a Recommended Dietary Allowance for biotin, so it set only Adequate Intakes. ODS lists the Adequate Intake as 30 mcg for adults 19 and older, including during pregnancy, and 35 mcg during breastfeeding. It also reports that the board could not set an upper limit because there is no evidence in humans that biotin is toxic at high intakes. Source [1]
Raw egg whites block biotin absorption
ODS explains that avidin, a protein in raw egg whites, binds tightly to biotin and prevents its absorption. Cooking changes avidin so that it no longer interferes. Source [1]
Some groups are more likely to run low on biotin
ODS names people with biotinidase deficiency, a rare inherited disorder that stops the body releasing free biotin, people with chronic alcohol exposure, and pregnant and breastfeeding women. It reports that at least a third of pregnant women develop marginal biotin deficiency despite normal intakes, and says more research is needed to understand what this means clinically. Source [1]
Sources
- Biotin: Fact Sheet for Health ProfessionalsNIH Office of Dietary Supplements, 2022 · Health authority summary · Primary source
- Biotin for Hair Loss: Teasing Out the EvidenceThe Journal of Clinical and Aesthetic Dermatology, 2024 · Narrative review · Not counted toward ratings
- Influence of biotin intervention on glycemic control and lipid profile in patients with type 2 diabetes mellitus: A systematic review and meta-analysisFrontiers in Nutrition, 2022 · Meta-analysis · Primary source
- Effects of water-soluble vitamins on glycemic control and insulin resistance in adult type 2 diabetes: an umbrella review of meta-analysesAsia Pacific Journal of Clinical Nutrition, 2025 · Systematic review · Primary source · Certainty: moderate
- Dietary interventions for multiple sclerosis-related outcomesCochrane Database of Systematic Reviews, 2020 · Systematic review · Primary source
- Testing for Biotin Interference in In Vitro Diagnostic Devices: Guidance for IndustryU.S. Food and Drug Administration, 2020 · Health authority summary · Primary source
Page history
Show all 2 changes to this page
- — Drafted. Hair, nails, skin and progressive multiple sclerosis rated insufficient; blood sugar in type 2 diabetes rated limited.
- — Published.