Biotin (vitamin B7) is a B vitamin the body needs to break down fats, sugars and amino acids. As a supplement it is used to cover low intake and is widely marketed for hair, skin and nails, where the evidence is limited.
Also known as: vitamin B7, vitamin H.
There is no RDA. ODS lists an Adequate Intake of 30 mcg a day for adults, 30 mcg in pregnancy and 35 mcg while breastfeeding. No upper limit was set, because there is no evidence in humans that biotin is toxic at high intakes. Biotin comes alone, in B-complex products and in multivitamins; ODS says the body absorbs nearly all of an oral dose, even up to 20 mg a day.
It is sold in the US as a dietary supplement. Under the 1994 dietary supplement law (DSHEA), FDA does not approve dietary supplements before they are marketed, and the maker, not FDA, is responsible for safety and labeling. There is no FDA-approved biotin pill for general use.
On hair and nails, ODS says hair loss, skin rash and brittle nails are signs of biotin deficiency, which is rare. The evidence for biotin for brittle nails comes from three small studies with no placebo group that did not check whether people were low in biotin to begin with.
The main caution is lab tests. ODS says high intakes of biotin can interfere with lab tests that use biotin-streptavidin technology, which are common for thyroid hormones, vitamin D and other markers, giving falsely high or falsely low results. Case reports describe test results that falsely looked like Graves' disease in people taking 10 to 300 mg a day, and a single 10 mg dose interfered with thyroid tests done within 24 hours. According to FDA, a person taking high-dose biotin died after a troponin test (used to diagnose a heart attack) gave a falsely low result. Tell whoever orders your blood work if you take biotin. Some seizure medicines (carbamazepine, primidone, phenytoin and phenobarbital) are linked to lower biotin levels (ODS).
We could not find a single published half-life or time to peak for biotin that applies to a supplement dose, so we do not list one. ODS notes that large oral doses raise blood levels of biotin and its breakdown products, which is why it can affect lab tests.
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