I use ReNEWMAN. They are based in Atlanta and have a pretty large network of doctors nationwide. You can find them at renewman.com. They have been very professional so far and seem legit. I worry a little that at some point the FDA or another arm of the government may clamp down on this whole area of medicine which is being advanced under the name of anti-aging or whatever. I could be wrong, but it never hurts to have a backup.
