I am currently taking clomid and I know that it can give you false positives on OPK, so you aren't supposed to start testing till 3 days after you finish your last pil. Femara probably works the same way.
Thanks so much for letting me know. My OB/GYN didn't return a call yesterday and I've been wondering. GL!
Well I have been on 3 cycles of Femara starting CD3-7. I go for US on CD12 and always get a very big follicle. I am instructed to start OPK only on CD10 which is 3 days after my last dose. Femara stay in your body for apprx 48 hr. Maybe it does give a false positive on OPK and that why they ask me to start testing only 3 days after last dose.