Assuming you are taking anastrozole. Its half life is approximately 2 days. So after 10 days you will have very little residual from your previous dosage. I would add to add some more time in order for things to adjust. In my experience being conservative 3 weeks should be enoughHow long after making a switch in AI does it take for E2 to steady? I was on .125mg EOD and now switched to .25mg EOD. Just curious how long I should wait to test E2 again.