Doctors (dermatologists)do recommend biotin sometimes. I've received many notes on RX forms for it over the years.

Zinc is really a big player for hair too. Some drugs deplete zinc.
ACE inhibitors for blood pressure, steroids, estrogens, and some antiseizure drugs deplete zinc. If a person takes alot of acid blocking drugs for GERD, this inhibits zinc absorption from food.

Vegetarians can become low in zinc because 1) zinc is more prevalent in animal sourced foods, and 2) the phytates in veggies complex zinc chemically and reduce its absorption to some extent.

People using lipoic acid may become low in biotin. They share the same transporter in the body, so if you use lipoic acid, biotin taken at another time of day, may be a good idea.

between the vit e and Biotin and the Bosely shampoo my hair is feeling great and thicker . The gal that does my hair was shocked ..