When to start doing opk?

Question

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The earliest I've ovulated is CD 17. I usually ovulate between CD 17-18. luteal phase 13-14. My cycle is usually 30-31 days but it's been whacky latley coming earlier than usual so now my average cycle lenght is 27. when should i start using opks?

Answer

I usually ovulate late in my cycle, around cd 19-20. I start using opks on cycle day 10 just in case my body has an off month.