Biotin only works if that's what you're lacking. Most often hair supplements are taken in combination, since we don't know what nutrients we might be lacking. A good one, for example, is Ultra Hair by Nature's Plus, but there are several good ones. You might also want to take a good look at the shampoos and such you're using -- many can cause problems. Eating the wrong fats can block the follicles -- remember, the hair you can see is dead, the live part is under the scalp at the follicle. A Chinese herb called fo ti, or shen min, has helped some people. And if it is a nutrient deficiency, don't expect quick results -- nutrient health takes time -- and don't think if some is good, a lot is necessarily better. It depends. Taking a huge amount of anything can throw other nutrients out of balance.
I am personally very cautious about taking excessive doses of anything. Biotin is very good for hair, nails and skin. You might also want to take BioSil (the only bioavailable form of silicon) for the same reason. I use both, but only take 1000 mcg biotin. The important thing in looking for results is time. I am not talking weeks, but months, and even years. For instance, BioSil got rid of a very nasty liver spot, but it took six months. It completely cured seriously bad varicose veins, but it took two years. Results for hair and nails for both biotin and BioSil are quicker - but be patient. And don't overdose.
http://www.livestrong.com/article/542800-the-side-effects-of-high-potency-biotin/