I like Cat's suggestion of getting both estradiol tests done. Ideally, you would want them done simultaneously. But even getting them done on different days - as long as testosterone levels, hormone therapy (or lack therof) and body fat are similar, we can assume that estradiol levels are as well. So from doing this, I know that the regular test puts my estradiol about 30% higher than the sensitive test. Of course, this ratio can vary from person-to-person and I have even seen people get higher results on the sensitive test (even with a simultaneous blood draw). But once you know it, you can go back to the regular test and have a good idea of where you would place on the other. Of course if you are one of those people whose testosterone levels vary a lot, you would really need to get the two estradiol tests done at the same time (since varying testosterone levels will result in varying estradiol levels).