I found this on Web MD:
30 mcg per day
Biotin is a coenzyme and a B vitamin, also known as vitamin H. As a supplement, biotin is sometimes used for diabetes, brittle nails, and other conditions.
Why do people take biotin?
Biotin plays a key role in the body. It supports the health of the skin, nerves, digestive tract, metabolism, and cells. Biotin may also help to treat some types of nerve pathology, such as the peripheral neuropathy that can result from kidney failure or diabetes.
Biotin supplements have been studied as a treatment for a number of conditions. In people with type 2 diabetes, early research suggests that a combination of biotin and chromium might improve blood sugar. On its own, biotin might decrease insulin resistance and nerve symptoms related to type 2 diabetes. More research needs to be done. Some preliminary evidence suggests that biotin might help strengthen brittle nails. Other uses of biotin -- for conditions like cradle cap, hepatitis, hair loss, and depression -- are unsupported or untested.
However, most people don't need biotin supplements. We get biotin in foods naturally. Our bodies also recycle the biotin we've already used. Genuine biotin deficiency is quite rare.
Pregnant women sometimes have low levels of biotin, so some take biotin supplements. The benefits and risks aren't clear.
How much biotin should you take?
The Institute of Medicine has set an adequate intake (AI) for biotin. Getting this amount from diet, with or without supplements, should be enough to support good health.
Depending on your case, your doctor might recommend a higher dose. For diabetes, for example, one study used 2 milligrams in combination with 600 micrograms of chromium.
Even at high levels, biotin appears to be fairly safe. Researchers don't know at what dosage biotin might start to pose health risks.
Can you get biotin naturally from foods?
Biotin occurs naturally in many foods. Wheat germ, whole-grain cereals, whole wheat bread, eggs, dairy products, nuts, Swiss chard, salmon, and chicken are all sources of biotin. The biotin in food is usually attached to protein and has relatively poor absorption.
What are the risks of taking biotin?
Side effects. Biotin seems to be safe and well-tolerated, even at fairly high levels. The maximum safe dose of biotin is unknown.
Risks. If you have any medical conditions -- or are pregnant or breastfeeding -- check with a doctor before using biotin supplements. Don't give biotin to a child unless a pediatrician recommends it.
Interactions. If you take any drugs regularly, talk to your doctor before you start using biotin supplements. Biotin might weaken the effect of some cholesterol drugs. Conversely, many drugs can lower biotin levels, including some antibiotics and medicines for acne. Some epilepsy drugs may decrease biotin absorption from food. A supplement, lipoic acid, may also increase the need for biotin. Eating raw egg whites on a regular basis can also lower biotin levels in the body.
