Day "21" bloods - how accurate does the day need to be?

[Alexandra6]

Hi, I'm on clomid for the first time, so no idea how long my cycle will be. I think I ov'd last week - I had a scan on Monday where they saw a good sized follie (on day 18) and then I got a smiley face OPK on Tues. So not sure exactly when I ov'd and when I should go in for my day "21" test, which should be 7 days after.

Does anyone know if you can be a day or two 'out' and still have an accurate test? What day would you go on? Thanks - just really want to be sure the clomid is working!

The "Day 21" test is based on assuming that you ovulate on Day 14, so you are right that the test should be done 7 days after ovulation.

Progesterone, the hormone the test is looking for, builds up after ov and peaks 7 days later, so your best chance of getting a good result is around this day, rather than the arbitrary "Day 21".

Thanks - totally understand that, but the prob is I'm not sure exactly when I ovulated! I got an smiley OPK last Tuesday lunchtime but you don't ov exactly then do you? I think Weds would be the ideal day but it's really tricky for me to get there because of work stuff (annoying!) so do you think this Tues would still give an accurate reading? Really appreciate any advice

In all honesty, all a "Day 21" test is looking for is a high enough progesterone reading that can confirm you definitely ovulated.

I've had "Day 21" tests taken a few days either side of the supposed date (usually due to falling at a weekend) and there is still plenty of hormone to give an accurate reading.

They usually say an OPK gives you 24-48 hours notice (depending on when you detect the surge) so is say either Tuesday or Thursdsy will be absolutely fine.

I'd assume you oved on Weds or Thursday, so the best time for the test would be a week after that.

Thanks, in that case I'll try not to stress too much if I can't make it to the hospital exactly 7 days after I ovulated if you think it will still be accurate enough a day either side

Would not use OPKs at all whilst you are on clomid as this can affect hormone levels (precisely the one that this kit reads) markedly. It could well give you a misleading result.

If they scanned you on day 18 then the blood test should be done three days post that scan (or thereabouts). A day or two either side won't make any difference to the overall result.

Stick to the day 21 test instead; they should also be doing a series of internal ultrasound scans to ensure that an egg is leaving the ovary.

If they did scan you on day 18 as well, they should have told you at the time when to next come in to have the blood test done.

Attila, I don't see the sense in going for a scan 3 days after a follie is seen. If the follie is still there, the OP hadn't ovulated by that point (but was probably going to soon as it was a good size) so the "day 21" test really needs to be a bit more than a week after this scan. The test is trying to catch the progesterone peak, which is usually 7 days post-ov.

Yes the last scan on day 18 was an ultrasound (had three of these in total) and the follicle was 18mm, so mature on day 18. The consultant said to do OPKs and then come back 7 days after ov, for day "21" tests (or 7 days after that scan if OPK's didn't work, as he thinks ov was going to happen quite soon based on size, he just couldn't say exactly when of course).

I've never had a positive OPK and I have heard they can be inaccurate for PCOS/clomid BUT was really hoping that combined with the scan and a bit of stomach cramping on the Weds, meant I'd ovulated?? I really hope so! Was just wondering whether the day "21" is still accurate if you go either 6 or 8 days after ov but it sounds like it is?

18mm is near optimum size for a follicle (ideal size is about 20mm).

Hopefully the day 21 will show ovulation has occured that month, are they going to do any more ultrasound scans this month?. As you are so near to optimum size they should hopefully fit in another scan for you to see how that dominant follicle has progressed.

Think they should be advising you better on when exactly you should go in to have the day 21 test done though.

Regular ultrasound scans and blood tests should provide an accurate picture of when and if you're going to ovulate that particular cycle.

I would ask the gynae about the feasilibility of using OPKs when using clomid at the same time.

Will keep my fingers crossed for a positive ovulation result:).

Thanks Last Monday (day 18) was my final scan - he said it was big enough to discharge me and I should ovulate soon. He recommended OPKs so I went home and did them and was so happy when I got a smiley face the next day and a crampy feeling the following day. Just really, really hope I did ovulate!