Can anyone talk to me about a CD 21 blood test please?

[forcookssake]

Following a trip to my doctor I have had this test. I didn't ask what it was actually measuring.Can anyone enlighten me please?

It measures progesterone and should ideally be done 7 days after ovulation, if you know when that is. That would be day 21 on a textbook 28 day cycle with ov on day 14, hence the name.

A level over 30 is usually taken to confirm that ov has occurred, but I've seen women on this board be told their prog levels are too low to indicate ov and then they conceived that month.

The test measures progesterone levels, it should be done between 6 & 9 days after predicted ovulation. Which for many women would be around day 21 if ovulation occurs on day 14, this assumes a 28 day cycle.

The result will indicate if ovulation occurred or not, as there is a rise in progesterone following ovulation. Progesterone reaches a peak after 7 days then starts to fall again unless pregnant occurs. The day 21 test is an attempt to catch the peak level of progesterone.

Thank you both that is really useful.
I think I might need to recount my days. And possibly request a rerun...
Anyhow thanks