Biotin
Summary
Biotin is a B vitamin with an adult Adequate Intake of 30 mcg/day, while some hair supplements contain 10 mg. Evidence for hair or nail benefit in people without deficiency is thin. FDA warns that high-dose biotin can distort lab tests, including a troponin test linked to a patient death.
Key facts
- Adequate Intake 30 mcg/day (35 mcg while breastfeeding); no UL set[1]
- High biotin intake can falsely raise or lower immunoassay results; FDA reported a death after a falsely low troponin test[1][2]
- Reported benefits come mostly from people with deficiency or underlying conditions[3]
- Long-term carbamazepine, phenytoin, primidone or phenobarbital use was linked to lower biotin levels[1]
- 0 graded human outcomes on this page
- October 11, 2026
How it works
EstablishedBiotin is a cofactor for carboxylases involved in fatty-acid synthesis, gluconeogenesis and amino-acid breakdown. Many lab immunoassays use biotin-streptavidin binding, which explains test interference.[1][4]
What the human research says
Human trials only, one row per outcome. The form column shows what each trial actually tested. Grades follow our evidence-grading policy.
No human trials met our inclusion bar yet.
Forms
| Form | Elemental % | Absorption (human data) | GI tolerance | Studied for |
|---|---|---|---|---|
| D-biotin capsules or tablets | Varies | No head-to-head human absorption data between products in the sources cited here. | No adverse effects from high intakes were established by the FNB; the main risk is lab-test interference.[1] | Small nail studies and deficiency correction |
Studied doses
Doses studied in human trials ranged from intake-level amounts near the 30 mcg Adequate Intake to 2.5 mg/day for 6–15 months in small brittle-nail studies.[1]
Intake reference: Adults 19+: Adequate Intake 30 mcg/day (30 mcg in pregnancy, 35 mcg while breastfeeding). No UL; the DV is 30 mcg.[1] NIH ODS fact sheet (updated January 10, 2022).
Interactions
Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.
Medicines
- AnticonvulsantsNIH fact sheetLong-term use was associated with lower serum biotin levels.[1]
Who should be careful
Talk to your pharmacist or clinician before starting a supplement, especially if you take prescription medicines.
Where to buy Biotin
Products from brands we partner with that contain Biotin. Listing a product is not a claim that it works; check the amount per serving against the doses studied above, and the label for other ingredients.
- SupersmartPaid linkBiotin1 capsule: 10 mg biotin (about 333 times the 30 mcg Adequate Intake); 120 servings. Tell your clinician before blood testsShop at Supersmart (opens in new tab)Price and label checked 2026-10-11 on the brand’s site.
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Frequently asked questions
Does biotin help hair growth?
Benefit has been reported mainly in people with deficiency or certain conditions; evidence in healthy people is thin.[3]
How much biotin do adults need?
The Adequate Intake is 30 mcg/day, far less than the 10 mg in some hair supplements.[1]
Can biotin affect lab tests?
Yes. High doses can give falsely high or low results on tests such as troponin and thyroid panels, so clinicians should know about it.[1][2]
Is there an upper limit for biotin?
No UL has been set because adverse effects from high intakes were not established.[1]
Sources
- [1]Biotin: Fact Sheet for Health Professionals. NIH Office of Dietary Supplements, 2022. fact-sheet
- [2]UPDATE: The FDA Warns that Biotin May Interfere with Lab Tests. U.S. Food and Drug Administration, 2019. safety-communication
- [3]The Infatuation With Biotin Supplementation: Is There Truth Behind Its Rising Popularity? A Comparative Analysis of Clinical Efficacy versus Social Popularity.. J Drugs Dermatol, 2017. review
- [4]Immunoassay design and biotin interference.. Adv Clin Chem, 2022. review
What changed
- First draft. Every PMID checked against NCBI E-utilities (title, journal and year taken from the PubMed record) and each evidence row written from its PubMed abstract.