Biotin (also known as vitamin B7 or vitamin H) is one of the B vitamins. It is involved in a wide range of metabolic processes, both in humans and in other organisms, primarily related to the utilization of fats, carbohydrates, and amino acids. The name biotin, borrowed from the German Biotin, derives from the Ancient Greek word (bíotos; 'life') and the suffix "-in" (a suffix used in chemistry usually to indicate 'forming').
Biotin is classified as a heterocyclic compound, with a sulfur-containing tetrahydrothiophene ring fused to a ureido group. A C5-carboxylic acid side chain is appended to the former ring. The ureido ring, containing the −N−CO−N− group, serves as the carbon dioxide carrier in carboxylation reactions. Biotin is a coenzyme for five carboxylase enzymes, which are involved in the catabolism of amino acids and fatty acids, synthesis of fatty acids, and gluconeogenesis. Biotinylation of histone proteins in nuclear chromatin plays a role in chromatin stability and gene expression.
The US National Academy of Medicine updated Dietary Reference Intakes for many vitamins in 1998. At that time there was insufficient information to establish estimated average requirement or recommended dietary allowance, terms that exist for most vitamins. In instances such as this, the academy sets adequate intakes (AIs) with the understanding that at some later date, when the physiological effects of biotin are better understood, AIs will be replaced by more exact information. The biotin AIs for both males and females are: 5 μg/day of biotin for 0-to-6-month-olds, 6 μg/day of biotin for 7-to-12-month-olds, 8 μg/day of biotin for 1-to-3-year-olds, 12 μg/day of biotin for 4-to-8-year-olds, 20 μg/day of biotin for 9-to-13-year-olds, 25 μg/day of biotin for 14-to-18-year-olds, and 30 μg/day of biotin for those 19 years old and older. The biotin AIs for females who are either pregnant or lactating, respectively, are: 30 μg/day of biotin for pregnant females 14-to-50-years old and 35 μg/day of biotin for lactating females 14-to-50-years old.