Well, I think that differs from person to person, but i'm on ortho tricyclene lo and on my first pack, I don't think I started until the very last inactive pill or at least the next to the last one. Just be prepared, I guess for starting anytime. Since this is your first pack, though, you may not even start at all and you may end up spotting throughout the active pills, it just depends. Everyone reacts differently to birth control pills.