Unless you're on implant/pellet administration of estradiol, it is really impossible to measure and determine what your levels would be, and what to make out of that. 1.5 hours after you would take a pill sublingually (and by that I mean successufully, not swallowing it all) your peak levels might just go into the 1000 pg/mL or even 2000+. 8 hours later your levels might show at 100 pg/mL. So its really not useful information in any serious way, except if you always take it at exact same time, like exactly 4 hours before blood test. Even that might not be much better. Its the same story with injections.. how do you determine what your levels are really, on which day, day 2, day 4, day 5 after injection. I thought before that patches might be better for that, for more constant blood serum, but my endo explained and enlightened me that it's really the same s***. So its mostly useless info, and its that much more important to watch the liver tests, prolactin, etc... This is the thing that shows you if anything HRT related goes wrong. And the only thing that really tells you that HRT goes right are changes that are happening, or aren't happening, in which case it simply means HRT isn't doing what it should. Important thing is of course having the appropriate expectations.