OPK Testing

We are looking to do IUI this month and the doctor's office suggested we use Clear Blue Advanced Digital and test the 2nd MU 1 hour after FMU. 2nd is normally around 6:30-7am. Testing this way has now pushed out my expected ovulation by 3 days.

I was using easy@home OPKs and would normally test around 10:30 am. My expected ovulation day would only move up/down by a day.

How has your doctor guided you to test? Have you seen a difference in expected ovulation with different tests?