Opk's - when to start testing?

Question

I've been tracking my periods on glow for about 8 months and my avg cycle is 37 days. My opk directions' chart says to start testing LH surge 20 days after start of last period ... But glow says my fertile days are like days 13-19 of my cycle!!? Is glow off? Have my green days been wrong ? Anyone else notice discrepancy ?

Answer

I've always been told to start OPK's on CD10. And track them until AF shows up.

Answer

If you have 37 day cycles I would start testing your LH on CD 10 at the earliest.

Answer

If your aren't sure around the time you ovulate you might try starting your opk as soon as your period ends