My dr wants to do some blood tests to determine if I'm ovulating or not. But I was just wondering, how can they tell for definite via a blood test? If I use opk's, I always get a strong test line when I'm supposed to be ovulating but I know that that doesn't tell me 100% that I am, just that my LH levels have surged. Surely that's all a blood test is going to tell me too? She also wants to do it around Day 20-21 of my cycle, I usually get my LH surge around day 15. How come she wants to do it way after I supposedly ovulate? Sorry if these are stupid questions, I'm new to all of this! I believe my tubes are blocked with scar tissue due to a d&c and that my body IS ovulating but the egg can't get out, hence always getting the surge but not getting pregnant. Are these blood tests going to be able to actually tell me anything I don't already know?