Question about CD21 bloods

[magicvw]

CD1 for me was 19th August, so my doc has told me to go for my cd 21 bloods on 8th September.

But I was wondering, since I temp and I know when I ov, if I find I ov on a day which is not cd14, should I use that date and go at 7dpo?

From my last 5 cycles i have ov'd on cd 12, 13 and 14 once each, and twice on cd16. So if I ov on cd 16 this month then 8th September i will only be 5dpo-so that would affect my results wouldn't it?

HELP!!!!

 

[Tishimouse]

My understanding of this is that the CD21 is calculated based on a 28 day cycle.

Therefore, when I had mine done, I worked out my day of ovulation on FF chart and know that I have a 14 day luteal phase. I therefore had my blood test 7 days before my AF was due. That way I ensured I had the test carried out at the right time to measure the correct hormone.

My doctor agreed with this principal.

 

[magicvw]

My cycles average out at 26 days and the last 2 have been 24 and 25 days... Now i'm getting more confused So do you think I should be going early than the 8th sep? THanks Tishimouse!

 

[FJL]

My cycles are 24-27 days and when I had 21 day prog test (it happened to be a 24 day cycle that month) my prog was at 21 which is a little on the low side but still normal. FS said had I have gone a few days earlier it would've been higher.

So yep, going a few days early would give you a more accurate reading.

 

[magicvw]

Thanks FJL! So if I understand correctly, the prog peaks at 7dpo then starts to drop until af?

I've emailed a gp friend to double check what to do. Another annoying thing is that the 8th is a monday, and the clinic is closed sat and sun, so it will be cd18 or cd21. Hmmmm.

 

[FJL]

Yep, thats right. When an egg is not fertilized, progesterone levels start to drop which allows the lining of the uterus to shed and AF rears her ugly head! So the earlier you test before AF, the higher your prog levels should be. So to go 7dpo would be a good idea.