Technically the hormones in the birth control pill can be effective after seven days, but it's best to wait a whole pack before having sex without additional birth control.
Taking the whole pack not only lets you get into the habit of taking it at the same time everyday (necessary for the pill to be fully effective), but it also gives your body time to adjust to the hormones and you can get an idea of how it affects you.
At Scarleteen, we advise that you take the pill for a month before considering it fully effective. In the meantime, if you're going to be sexually active, use a back up method.
There's some tomatoes Chemically engineered - They come out square to fit in boxes.
There's some people chemically engineered -
They come out square
to fit in boxes. -Dan Bern