I asked my oncologist this same question regarding effective dosage. I’ve been taking Anastrozole for almost 2 years. 1mg for everyone does not seem right. I had never had my estrogen level tested, so how do doctors know if Anastrozole is working. I’m 68 snd ‘maybe’ my estrogen was fairly low when I had my surgery. There was not a baseline to compare to now. My oncologist said ‘he takes it for granted’ that it is working. I requested estrogen test and had test June 24th. Waiting on results. I’ll post when I get results. Good luck.