Does it take 7 days or 1 month for birth control to protect you from pregnancy and why do i sometimes hear both answers for this question?

Basics: The pill tries to prevent egg release by establishing a stable hormone level in your blood. No egg= no pregnancy. Some pill makers suggest a week or 2 will do. Many OBGYN's advise a month using a backup to be sure your body adjusts to the pill & no egg is or was released. If you really need the pill to work I would be cautious of taking short cuts.