Hello I recieved the birth control shot for the first time today and I have some questions about it? I want to know how long you have to wait to be sexully active so it ill be effective and I also want to know how effective it is. I want to know the prece

It depends. It depends on when in your cycle you started the shot. If you started on the first day of bleeding, it's effective right away. If later in your cycle, it typically takes 7 days to take effect, so use back up prior to then. It also may depend on when you last had sex, and what you used for protection.
Research . Research shows that the depo-provera shot is over 99% effective. If the shot is given within 5 days of the first day of your last menstral cycle, then it is immediately effective and will protect you from pregnancy. The shot prevents pregnancy for 14 weeks, and should be administered every 12 weeks to maintain effectiveness. Having said that, if you did not recieve your shot within 5 days of the first day of your last menstral cycle, then the shot will be most effective 2 weeks after administration. .