Why can’t we OPK with FMU?

[coconuttymummy]

I know that FMU doesn’t work for OPK tests but I’m wondering why, as you would have thought your most undiluted urine would give a stronger result.

I’ve actually tested it myself (I’m nosey like that) and even the days that I have high readings with the 2nd or 3rd wee of the day (sorry TMI) I only ever get a super faint test line with FMU that same day.

So, I’m just bored and wondering “why is this”?! x

I think ita because that your LH surge usually happens later on in the day so you might miss it with FMU?

But i found that my peak happened with FMU some cycles so i personally would test a few times a day haha!

Most tests actually do say to use FMU.....but precious poster is right than most LH surges happen in the afternoon

I think it can vary! I tried OPKs for the forst timw this cycle and my peak actually happened over night, so the strongest results I had were with the last wee of the day at 11pm, and then with FMU. The second wee of the day was really weak again!

I have heard that a lot of women do have their surge in the afternoon though.