Biotin is necessary for cell growth, the production of fatty acids, and the metabolism of fats and amino acids. It plays a role in the citric acid cycle, which is the process by which biochemical energy is generated during aerobic activities. Biotin not only assists in various metabolic reactions, it also helps transfer carbon dioxide in the blood and is helpful in maintaining a steady blood sugar level. Biotin is often recommended for strengthening hair and nails. Consequently, it is found in many hair and nail vitamins on the market.

Deficiencies are extremely rare, as intestinal bacteria naturally produce an excess of the body's daily requirement.
Biotin can be found in a variety of foods that are normally consumed. Estimates are that the typical U.S. diet provides roughly 40 micrograms a day.

There are only a couple of foods that contain biotin in large amounts, including royal jelly, egg yolk, and brewer's yeast. High levels are also found in milk, liver, and some vegetables like Swiss Chard. Additional sources include tomatoes, romaine lettuce, carrots, almonds, onions, cabbage, cucumber, and cauliflower. Goat's milk, raspberries, strawberries, halibut, oats, and walnuts also contain some.

There do not appear to be any toxic effects from ingesting unusually large amounts of this nutrient.

The incidence of low circulating biotin levels has been associated with alcoholics, in those with a partial gastrectomy, burn patients, epileptics, the elderly, and athletes. Pregnancy and lactation may also be associated with an increased demand for biotin. Additionally, smoking may further accelerate deficiencies, especially in women.