It was one month for me to get on a therapeutic dose of E, and no letter was necessary. It was one session, one call to the endo, a 2 1/2 week wait for the appointment, a week for the lab work, and almost another week before I had the prescription in hand because my endo is so busy.
I decided to go permaJill about 2 months later, which required a letter and a total of 12 sessions.