from everything ive heard it protects great againts getting pregnant, side affects suck worse though from what ive heard from friends and family that have used the shot also when getting off the shot to become pregnant that will take a while to get your body back to normal as well . also it is normal as well to miss periods so dont neccesarily freak out if one is missed.

If she is on the shot, then you have not been having unprotected sex. Depo is protection. Depo is about 97-99.7% effective when used alone.

Tinkin is right about side effects though. Depo is not recommended for young women. Also, the FDA only recommends Depo as a long term form of birth control if a woman cannot use other forms of birth control for some reason as it can cause irreversible damage.