Biotin: Benefits, Dosage, and Safety

What biotin is

Biotin is an essential water-soluble B vitamin, also called vitamin B7, that is naturally present in some foods and available as a dietary supplement. In the body it works as a cofactor for five carboxylase enzymes. Because the Food and Nutrition Board found the available data insufficient to derive an Estimated Average Requirement and an RDA, only an Adequate Intake (AI) has been set for biotin.

What it does

• Serves as a cofactor for five carboxylase enzymes (propionyl-CoA carboxylase, pyruvate carboxylase, methylcrotonyl-CoA carboxylase, acetyl-CoA carboxylase 1, and acetyl-CoA carboxylase 2) that catalyze critical steps in metabolism
• Supports the metabolism of fatty acids, glucose, and amino acids
• Plays a role in histone modifications
• Contributes to gene regulation by modifying the activity of transcription factors
• Involved in cell signaling

How much biotin per day

These are population reference values from the NIH and the Dietary Reference Intakes. They are targets for healthy people, not personal prescriptions. The last column is the Tolerable Upper Intake Level, the most you should get from all sources combined.

Deficiency and who is at risk

Signs and symptoms typically appear gradually and can include thinning hair progressing to loss of all body hair; a scaly, red rash around body openings (eyes, nose, mouth, and perineum); conjunctivitis; ketolactic acidosis and aciduria; seizures; skin infection; brittle nails; and neurological findings such as depression, lethargy, hallucinations, and paresthesias of the extremities in adults. In infants, signs include hypotonia, lethargy, and developmental delay. The rash with unusual distribution of facial fat is known as biotin deficiency facies. Biotin deficiency is rare, and severe deficiency in healthy people eating a normal mixed diet has never been reported.

Who may need more

• People with biotinidase deficiency, who require lifelong oral biotin starting at birth (all US newborns are screened for this disorder)
• People with chronic alcohol exposure
• Pregnant and breastfeeding women, who may develop marginal deficiency despite adequate intake
• People taking anticonvulsant medications long term

Food sources

Organ meats, eggs, fish, meat, seeds, nuts, and certain vegetables such as sweet potatoes contain the most biotin. Examples per serving: cooked beef liver, 3 ounces (30.8 mcg); whole cooked egg (10.0 mcg); canned pink salmon, 3 ounces (5.0 mcg); cooked pork chop or hamburger patty, 3 ounces (3.8 mcg each); roasted sunflower seeds, 1/4 cup (2.6 mcg); cooked sweet potato, 1/2 cup (2.4 mcg); roasted almonds, 1/4 cup (1.5 mcg). Raw egg white contains avidin, which binds biotin and blocks its absorption; cooking denatures avidin.

Forms and absorption

Available in supplements containing biotin only, in B-complex products, and in some multivitamin/mineral products. The absorption rate of oral, free biotin is essentially 100%, even at pharmacologic doses up to 20 mg per day. In foods most biotin is protein-bound and must be released by gastrointestinal proteases and the enzyme biotinidase before the free form is absorbed in the small intestine.

Safety, excess and interactions

Too much

The Food and Nutrition Board was unable to establish a Tolerable Upper Intake Level because there is no evidence in humans that biotin is toxic at high intakes. Several studies found no adverse effects of 10-50 mg per day, and up to 200 mg per day orally or 20 mg per day intravenously in patients with biotinidase deficiency did not produce symptoms of toxicity. The main documented risk of high intake is not classic toxicity but interference with laboratory tests (see interactions).

Interactions to know

• Laboratory test interference: very high biotin intakes can interfere with immunoassays that use biotin-streptavidin technology, producing falsely high or low results for hormones such as thyroid hormone and for analytes such as 25-hydroxyvitamin D. Case reports describe results falsely indicating Graves' disease and severe hyperthyroidism in patients taking 10-300 mg per day.
• Thyroid function tests: even a single 10 mg dose has interfered with thyroid function tests taken within 24 hours; a study found falsely decreased thyroid stimulating hormone (mimicking thyrotoxicosis).
• Troponin and NT-proBNP: biotin can falsely lower troponin (used to diagnose heart attack) and NT-proBNP (used for heart failure); FDA reported a patient death after a falsely low troponin result attributed to biotin interference.
• Anticonvulsants: long-term treatment with carbamazepine (Tegretol, Carbatrol, Epitol, Equetro), primidone (Mysoline), phenytoin (Dilantin, Phenytek), and phenobarbital (Luminal, Solfoton) is associated with significantly lower serum biotin levels, likely due to increased biotin catabolism and inhibited intestinal absorption.
• Chronic alcohol intake inhibits biotin absorption and lowers biotin status.

How status is measured

No single reliable marker exists. In healthy adults, serum biotin is 133-329 pmol/L and urinary biotin is 18-127 nmol/24 hours. Abnormally low urinary biotin, or abnormally high urinary 3-hydroxyisovaleric acid (above 3.3 mmol/mol creatinine) or 3-hydroxyisovalerylcarnitine (above 0.06 mmol/mol creatinine), indicates deficiency. The most reliable individual markers are biotinylated methylcrotonyl-CoA carboxylase and propionyl-CoA carboxylase in white blood cells. Serum biotin is not a good indicator of marginal deficiency. Biotin status is not routinely measured in general practice.

Regulated as a dietary supplement ingredient under DSHEA, not as a drug; supplements are not FDA-approved to treat, cure, or prevent disease. The FDA Daily Value (DV) for biotin is 30 mcg for adults and children age 4 years and older. FDA does not require food labels to list biotin unless it has been added. FDA has issued safety communications warning that biotin can interfere with certain laboratory tests.

What the evidence supports

We grade the strength of evidence behind each common reason people take biotin, mirroring how the NIH describes it.