Biotin
Biotin deficiency is rare, and the evidence for biotin as a hair and nail treatment comes almost entirely from people who were deficient. The high doses sold for beauty do have one reliable effect: they distort common blood tests, including the troponin test used to diagnose heart attacks. Most people do not need a biotin supplement.
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What It Does
Biotin is the cofactor for five carboxylase enzymes that build fatty acids, make glucose from other substrates, and break down several amino acids. The enzyme biotinidase recycles it, and inherited biotinidase deficiency, detected by newborn screening, is the clearest cause of deficiency. Other causes are long-term consumption of raw egg whites, whose avidin binds biotin, chronic alcohol use, and some anticonvulsants. Deficiency shows up as thinning hair, a scaly rash around the eyes, nose, and mouth, and neurological symptoms.
The hair and nail evidence does not extend to people with normal status. A review of every published case in which biotin improved hair found that all 18 had an underlying cause, such as an inherited or acquired deficiency or a rare hair shaft disorder (Patel 2017). The nail data are small uncontrolled studies from decades ago (Lipner 2018). High-dose biotin was also tested as a drug: 300 mg a day failed to improve disability in progressive multiple sclerosis in a phase 3 trial (Cree 2020).
The real clinical issue is laboratory interference. Many immunoassays use biotin and streptavidin as a molecular glue, and excess biotin in the sample blocks it. Depending on the assay design, results come out falsely low (troponin, TSH) or falsely high (free T4, T3). In healthy adults taking 10 mg a day for a week, 9 of 23 susceptible assays gave clinically misleading results (Li 2017). Children on high-dose biotin had lab results that mimicked Graves' disease (Kummer 2016). FDA first warned about the problem in 2017, after reports that included a death linked to a falsely low troponin, and updated the warning in 2019 (FDA 2019).
Forms and Bioavailability
The standard supplemental form.
| Form | Absorption | Typical dose | Cost | Labels |
|---|---|---|---|---|
| D-Biotinbiotin, vitamin B7 | HighNearly completely absorbed at supplement doses by the sodium-dependent multivitamin transporter. | 30-100 mcg covers needs; products often hold 5,000-10,000 mcg | Low | 325 |
Labels column: number of labels named as biotin products that list this form. A product can list more than one form, and some labels do not state a form at all.
D-biotin is the only supplemental form and is nearly completely absorbed. It appears in most multivitamins at 30-300 mcg and in "hair, skin, and nails" products at 5,000-10,000 mcg, often alongside collagen.
Typical Dosing
| Group | Adequate Intake (AI) |
|---|---|
| Adults 19+ | 30 mcg |
| Pregnancy | 30 mcg |
| Lactation | 35 mcg |
| Upper limit (UL) | Not established |
Hair, skin, and nail products often contain 5,000-10,000 mcg (5-10 mg), more than 150 times the AI. A multivitamin with 30-100 mcg covers needs.
Food sources: beef liver, cooked eggs, salmon, pork, sunflower seeds, sweet potato, almonds.
What to Look For
If your hair is thinning, look for a cause before buying biotin: iron deficiency, thyroid disease, recent illness or childbirth, and androgenetic hair loss are all far more common than biotin deficiency. A standard multivitamin provides as much biotin as almost anyone needs.
If you take a high-dose product anyway, tell every clinician and lab. Many labs advise stopping high-dose biotin several days before blood work; ask yours. In an emergency with chest pain, mention biotin.
Red flags: 10,000 mcg gummies marketed for hair growth, and biotin stacked across a multivitamin, a hair product, and a B complex. Green flags: biotin at multivitamin-level doses, and lab testing for actual causes of hair loss.
D-Biotin
Effective for real deficiency at small doses. For hair in people without deficiency, there is no good evidence at any dose.
What to look for: 30-100 mcg, usually inside a multivitamin. Avoid milligram doses unless a clinician prescribes them.
Find on iHerb Affiliate linkProducts on Titrate
19,468 of the 214,745 labels in the NIH Dietary Supplement Label Database list biotin as an active ingredient (9,375 on market). 1,099 are sold as biotin products by name.
Top on-market labels, ranked by label completeness and simplicity:
- Biotin 1% Vitamin B7
- Biotin 10,000 mcg Powder
- Biotin 10,000 mcg Powder
- Biotin Capsules 10000 mcg
- High Potency Biotin 10 mg
Biotin does not have its own search category yet. Each product above links to its full label in the NIH database.
Related Tools
References
NIH Office of Dietary Supplements. Biotin: Fact Sheet for Health Professionals.
US Food and Drug Administration. UPDATE: The FDA Warns that Biotin May Interfere with Lab Tests: FDA Safety Communication.
Kummer S, Hermsen D, Distelmaier F. Biotin treatment mimicking Graves' disease. N Engl J Med. 2016;375(7):704-706.
Li D, Radulescu A, Shrestha RT, et al. Association of biotin ingestion with performance of hormone and nonhormone assays in healthy adults. JAMA. 2017;318(12):1150-1160.
Patel DP, Swink SM, Castelo-Soccio L. A review of the use of biotin for hair loss. Skin Appendage Disord. 2017;3(3):166-169.
Lipner SR, Scher RK. Biotin for the treatment of nail disease: what is the evidence? J Dermatolog Treat. 2018;29(4):411-414.
Cree BAC, Cutter G, Wolinsky JS, et al. Safety and efficacy of MD1003 (high-dose biotin) in patients with progressive multiple sclerosis (SPI2): a randomised, double-blind, placebo-controlled, phase 3 trial. Lancet Neurol. 2020;19(12):988-997.
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