How many mg of biotin do u need for hair loss and brittle nails daily?

5000 mcg daily: While the recommended daily dose of Biotin is about 30-35mcg, if you are experiencing brittle nails you may want to supplement with as much as 5,000 mcg a day. There are other reasons for brittle nails also including thyroid insufficiency for example.

5000 units/day: You can take more, but there is no convincing evidence that more is better.