How long should I wait after getting the shot to have sex?
If you get the birth control shot (also known as Depo-Provera) within the first 7 days after the start of your period, you’re protected from pregnancy immediately. Otherwise, you need to use some form of backup birth control — like a condom — whenever you have sex during the first week after getting the shot.
To get the shot’s full birth control powers, you have to remember to get a new shot every 12-13 weeks. That’s about every 3 months, or 4 times a year. If you go more than 15 weeks without getting your shot, your nurse or doctor may ask you to take a pregnancy test before getting another shot. If you had vaginal sex since the shot wore off (within the last 5 days), you can use emergency contraception.