Can a Day 21 blood test indicate a BFP?!

[VeryBerry22]

Or a) is it far too early, or b) they don't actually check for a BFP in a Day 21 test?!

It's not a HCG test..? It's a measurement of progesterone, which can be high for numerous non-pregnancy reasons. Also it's too early for detection of pregnancy in most people's cycles anyway.

I had a day 21 test done the cycle I ended up pregnant. It was only 29 so I thought I was out and was very surprised when I had a positive test a week later. I ended up on progesterone pessaries as my GP thought my level was low and I had 2 previous consecutive miscarriages. I'm 16 weeks pregnant now.