You may recognize vitamin B7 by its popular name of biotin. It is a water-soluble B vitamin found naturally in some foods and also in supplements. Biotin plays a vital role in assisting enzymes to break down fats, carbohydrates, and proteins in food. It also helps to regulate signals sent by cells and the activity of genes. 
An RDA (Recommended Dietary Allowance) does not exist for biotin because there is not enough evidence to suggest a daily amount needed by most healthy people. Instead, there is an AI (Adequate Intake) level, which is assumed to ensure nutritional adequacy.
UL: A Tolerable Upper Intake Level (UL) is the maximum daily dose unlikely to cause adverse side effects in the general population. There is no UL for biotin due to a lack of reports showing negative effects from very high intakes.
Biotin supplements are often glamorized as a treatment for hair loss and to promote healthy hair, skin, and nails. Although a deficiency of biotin can certainly lead to hair loss and skin or nail problems, evidence showing a benefit of supplementation is inconclusive. A handful of case reports and small trials have shown a benefit, but the study designs had weaknesses:
Despite the inconclusive evidence, biotin supplements remain popular. Between 1999 and 2016, the proportion of supplement users increased by nearly thirtyfold.  In November 2017, the U.S. Food and Drug Administration (FDA) issued a warning based on reports of biotin supplements interfering with laboratory blood tests, causing incorrect results. High doses have produced either falsely elevated or decreased blood levels, depending on the test. This has affected lab results of certain hormones, such as thyroid-stimulating hormone and vitamin D, as well as a biomarker for heart attacks called troponin.  Case reports of this occurrence showed people taking biotin amounts much higher than the AI level (30 micrograms daily or 0.03 mg) but in doses commonly found in supplements (10-300 mg). Biotin is often added to multivitamins and hair/nail/skin supplements. The FDA recommends that people inform their doctors at each visit of all supplements and doses they are taking.
A biotin deficiency in the U.S. is rare, as most people eat enough biotin in a varied diet. Alcoholism can increase the risk of biotin deficiency and many other nutrients as alcohol can block their absorption, and also because alcohol abuse is generally associated with a poor dietary intake. About a third of pregnant women show a mild biotin deficiency despite eating adequate intakes, though the exact reason is not clear. 
No evidence in humans has shown a toxicity of biotin even with high intakes. Because it is water-soluble, any excess amount will leave through the urine. There is no established upper limit or toxic level for biotin.
Those who frequently enjoy raw eggs in recipes for mayonnaise, Caesar dressing, or eggnog may want to reconsider. A protein in raw eggs called avidin can bind to biotin, preventing its absorption. Cooked eggs are not an issue because avidin is broken down when heated.
Biotin deficiency is very rare in the United States. Biotin deficiency can cause thinning hair and loss of body hair; a rash around the eyes, nose, mouth, and anal area; pinkeye; high levels of acid in the blood and urine; seizures; skin infection; brittle nails; and nervous system disorders. Symptoms of biotin deficiency in infants include weak muscle tone, sluggishness, and delayed development.
Hair, nail, and skin healthDietary supplements that contain biotin are often promoted to improve the health of your hair, skin, and nails, but there is little scientific evidence to support these claims. In a few small studies, some people with thin and brittle nails who took high doses of biotin had harder nails. Doctors have also reported that in a few cases, high doses of biotin have improved a rare hair disorder in children and skin rash in infants. More research is needed before biotin supplements can be recommended for any of these conditions.
Biotin has not been shown to cause any harm. However, supplements that contain biotin above recommended amounts may cause false results in some lab tests, including those that measure levels of certain hormones, like thyroid hormone.
Yes, some medications you take may affect your biotin levels, and biotin may interact with certain medications. For example, treatment for at least 1 year with antiseizure medications (used to treat epilepsy) can significantly lower biotin levels.
Tell your doctor, pharmacist, and other health care providers about any dietary supplements and prescription or over-the-counter medicines you take. They can tell you if the dietary supplements might interact with your medicines or laboratory tests, or if the medicines might interfere with how your body absorbs, uses, or breaks down nutrients such as biotin.
Most biotin in foods is bound to protein, although some dietary biotin is in the free form [1,3,4,6]. Gastrointestinal proteases and peptidases break down the protein-bound forms of ingested biotin into biocytin and biotin-oligopeptides, which undergo further processing by biotinidase, an enzyme, in the intestinal lumen to release free biotin . The free biotin is then absorbed in the small intestine, and most biotin is stored in the liver [1,3,6].
Intake recommendations for biotin and other nutrients are provided in the Dietary Reference Intakes (DRIs) developed by the Food and Nutrition Board (FNB) at the National Academies of Sciences, Engineering, and Medicine . DRI is the general term for a set of reference values used for planning and assessing nutrient intakes of healthy people. These values, which vary by age and sex, include:
The FNB found the available data to be insufficient to derive an EAR and RDA for biotin. For this reason, the FNB established only AIs for biotin. The FNB based its determination of AIs for all populations on the amount of biotin in human milk consumed by infants and then used body weight to extrapolate AIs for other groups . Table 1 lists the current AIs for biotin .
FoodMany foods contain some biotin. Foods that contain the most biotin include organ meats, eggs, fish, meat, seeds, nuts, and certain vegetables (such as sweet potatoes) [2,12]. The biotin content of food can vary; for example, plant variety and season can affect the biotin content of cereal grains, and certain processing techniques (e.g., canning) can reduce the biotin content of foods .
*DV = Daily Value. The U.S. Food and Drug Administration (FDA) developed DVs to help consumers compare the nutrient contents of foods and dietary supplements within the context of a total diet. The DV for biotin is 30 mcg for adults and children age 4 years and older . FDA does not require food labels to list biotin content unless biotin has been added to the food. Foods providing 20% or more of the DV are considered to be high sources of a nutrient, but foods providing lower percentages of the DV also contribute to a healthful diet.
Dietary supplementsBiotin is available in dietary supplements containing biotin only, in supplements containing combinations of B-complex vitamins, and in some multivitamin/multimineral products . The absorption rate of oral, free biotin is 100%, even when people consume pharmacologic doses of up to 20 mg/day biotin .
Pregnant and breastfeeding womenAt least a third of pregnant women develop marginal biotin deficiency in spite of normal biotin intakes; plasma and breastmilk concentrations of biotin decrease in lactating women, even when their dietary biotin intakes exceed the AI [2,18,22]. Additional research is needed to understand the clinical significance of these findings.
Signs of biotin deficiency include skin rashes, hair loss, and brittle nails [10,13]. Therefore, biotin supplements are often promoted for hair, skin, and nail health [16,23,24]. However, these claims are supported, at best, by only a few case reports and small studies.
High biotin intakes, and potentially even intakes greater than the AI, may pose another type of health risk . Supplementing with biotin beyond recommended intakes can cause clinically significant falsely high or falsely low laboratory test results, depending on the test. These incorrect results may lead to inappropriate patient management or misdiagnosis of a medical condition. The following section has more details on these interactions.
Even a single 10 mg dose of biotin has interfered with thyroid function tests administered within 24 hours of taking the supplement . A small study in six healthy adults who took 10 mg/day of supplemental biotin for 1 week found interference in several biotinylated assays, including falsely decreased levels of thyroid stimulating hormone (which could lead to a misdiagnosis of thyrotoxicosis) and N-terminal pro-brain natriuretic peptide (which could result in a failure to identify congestive heart failure) . According to the Food and Drug Administration (FDA), a patient with a high intake of supplemental biotin died following a troponin test (to help diagnose a heart attack) that gave a falsely low result because the test was subject to biotin interference .
FDA advises health care providers to ask their patients about any supplements they may be taking that contain biotin and to consider biotin interference as a possible source of error if laboratory test results do not match the clinical presentation of the patient .
Biotin can interact with certain medications, and some medications can have an adverse effect on biotin levels. One example is provided below. Individuals taking this and other medications on a regular basis should discuss their biotin status with their health care providers.
AnticonvulsantsIn a study in 264 people with epilepsy, anticonvulsant treatment for at least 1 year was associated with significantly lower serum biotin levels than in control group patients . The anticonvulsants used included carbamazepine (Tegretol, Carbatrol, Epitol, Equetro), primidone (Mysoline), phenytoin (Dilantin, Phenytek), and phenobarbital (Luminal, Solfoton) as well as combinations of these medications. A few other, smaller studies, have found similar results [40,41]. The reason could be that anticonvulsant treatment increases biotin catabolism, which leads to reduced biotin status and inhibition of intestinal biotin absorption [40,42]. 041b061a72