On the website, they are a bit more laid back on the rules. They say that you MAY want to go off the pill. It seems they are worried about estrogen affecting your ability to loose weight. (Atkins Diet Revolution)

And once you go into ketosis, you are supposed to be able to tell because your breath changes. Or you can buy these strips of paper called ketostix (used like a pregnancy test), that tell you if you're burning fat (in ketosis).