Many individuals take Biotin, believing it will improve their hair, skin or nails. Although a good multivitamin will cover the daily need for 30 mcg of Biotin, many Biotin-specific supplements provide 1000 to 5000 mcg per dose. Taking large mega-doses of any vitamin and mineral should not be done without your health care provider’s knowledge. This article describes how taking large doses of biotin can impact important thyroid testing results and even result in inappropriate medical treatment. Read up, and then remember to update your health care team on all supplements you take.