If you have a 31 day cycle, then the test should be done on cycle day 24.
I worked in a lab in Germany and I know for sure when to test for Progesterone.
Check out this chart, you will see that Progesterone is at it's highest in luteal phase, one week after ovulation resp. one week before menstruation. You need to know how much your Progesterone value can rise in luteal phase. To measure in follicular phase just doesn't make any sense, because as you can see in the diagram, Progesterone is low from cycle day 1-13 (without any fluctuations). But you want to know if you produce enough Progesterone in luteal phase and then you can also calculate the Progesterone / Estradiol ratio and you will know if you are estrogen dominant or not. Every woman has the same low Progesterone value in follicular phase, but not every woman can produce enough Progesterone in luteal phase. Some women produce just 3 ng/mL and others produce 20 ng/mL and you want to know how much you can produce.
![[Image: Image20.gif]](http://www.project-aware.org/images/Image20.gif)
I worked in a lab in Germany and I know for sure when to test for Progesterone.
Check out this chart, you will see that Progesterone is at it's highest in luteal phase, one week after ovulation resp. one week before menstruation. You need to know how much your Progesterone value can rise in luteal phase. To measure in follicular phase just doesn't make any sense, because as you can see in the diagram, Progesterone is low from cycle day 1-13 (without any fluctuations). But you want to know if you produce enough Progesterone in luteal phase and then you can also calculate the Progesterone / Estradiol ratio and you will know if you are estrogen dominant or not. Every woman has the same low Progesterone value in follicular phase, but not every woman can produce enough Progesterone in luteal phase. Some women produce just 3 ng/mL and others produce 20 ng/mL and you want to know how much you can produce.