A decent dermatologist will do, but aside from hair transplant, there’s only two drugs clinically tested and FDA approved : Minoxidil (Rogaine and other brands) and Propecia (Proscar, Finasteride, etc.), there are some interesting drugs too like Dutasteride or Follica but there aren’t enough studies yet.

If you’re into natural stuff, the only one that might be helpful is Saw Palmeto (there are capsules for sale in natural shops) because it contains anti androgens similar to the ones found on Propecia.

Quite frankly all the other stuff are either placebos or scams.