Now Foods Extra Strength Biotin is the best vitamin B supplement to give you healthier hair, skin, and nails, thanks to the highest concentration of biotin. The formula contains 10,000 mcg of biotin in one serving, a water-soluble vitamin that encourages energy production and promotes a healthy immune system. The supplement is suitable for vegans and doesn’t contain soy, eggs, dairy, nuts, soy, and gluten. It’s also kosher and non-GMO.