I've been taking 5000 mcg of Biotin a day for a couple years and I have to say I don't notice much improvement. I spoke with a woman today who takes 10,000 mg (5000 twice a day) and has gotten results. I'm considering doing this, but it does seem a bit excessive and I'm worried about toxicity. This is especially because I have a history of breast cancer and I'm just extra cautious. But has anyone here taken such a large dose of biotin and if so, has it made a difference?