The nurse at the OB GYN office told me to do the Estradial test on Cycle Day 3 and Progesterone on Cycle Day 21.
I told her that my cycles are short- 25 or 26 days. She told me that these tests are run on cycle day3 for Estradial and 21 for progesterone regardless of cycle length. Does this sound right?
That is how the tests are normally done, but it's only done this way because most people can't pinpoint ovulation (so the test is done based on a 28 day cycle). As long as you chart and know exactly what day you ovulated, the progesterone test should be done on the 7th day past ovulation.
Day 3 will be easy to define, no matter what your cycles are like. Define day 1 as the first day of true bleeding (not spotting) and day 3 is 2 days later.
But you're right in questioning the day 21 testing. If you ovulate extremely early (say CD 10), and you tested on day 21, then you would be testing progesterone on 11dpo. At this point, progesterone could have already plummeted and you'd get a falsely low result.
However, if you cannot pinpoint the exact day of ovulation, you'll have to do day 21, as you've got no other choice really. Day 21 is better than some other arbitrary day (hence the reason they do it this way).
I hope that's helpful.
Hi there! Although you posted a while back I thought I'd chime in. I just started going through the testing. My progesterone levels were checked over a two month period. Because my cycles vary anywhere from 25 days to 34 days my doctor told me to come in exactly 7 DPO for the test. So for example if I ovulated on day 17 I would count that day as the first day and go in exactly a week later for the progesterone test. Both times for me it was below what it should have been - 10.1 and 10. Needless to say I'm starting Prometrium at the end of this month. Hope you have found additional answers in the meantime!