How long is it supposed to it take for birth control pills to start taking effect?

One month: The truth is that you are usually safe in the first month, but we usually ask you to use protection for one month to be sure.

A week or less: If you start taking your pills on the first day of your period, they're effective immediately. If you start at any other time, you should use a backup method for 7 days. Many doctors say the whole first month, but the evidence says a week.