Day 21 blood test confusion! Help pls

[acaciabluebell]

Hi everyone, so my GP advised me to book my day 21 progesterone blood test for roughly 7 days after ovulation.

I could only get an appointment for 'day 22' when I will be 8dpo. Because my LP is only 12 days, it will be 4 days before AF.

Is this too late?? I read somewhere that it's supposed to be 7 days before AF?

Also, I have booked my 'day 3' test on what I predict will be day 1-2... Is this okay?

I think you need to ask your GP these questions as they'll be the ones to interpret the results. They'll need to know the 21 day progesterone was done 8DPO and that the day 3 bloods were done on day 1-2. Hopefully they can then account for any discrepancies with that information.

However... I can confirm that the 'Day 21' progesterone test is meant to be taken 7 days after ovulation. It's completely independent of luteal phase length. The '7 days before your period is due' is making the assumption of a 14 day luteal phase. A lot of people don't know when they ovulate or how long their luteal phase is so if you say to a doctor 'My cycle is 35 days' they'll order your 21 day progesterone for day 28 unless you give them an ovulation date/luteal phase length.

Also, if you haven't already it'd be important to mention your shortened luteal phase if you think it might be an issue. Mine was 11 days until I was diagnosed with a thyroid condition and started taking thyroid hormones. Last cycle it was 13-14 days 😊.

Good luck! Hope you get some answers / a good outcome!

FWIW I'd be surprised if doing Day 21 progesterone 8DPO would be a problem. It's only 1 day difference. Same goes for the day 3 ones. But definitely best to check with the GP as they'll be interpreting the results.

Thanks so much @Curiosity101 I really appreciate your response! Very informative!