The injection works for 12 or 8 weeks, depending on which type you have. It cannot be removed from your body, so if you have any side-effects, they may continue during this time and for some time afterwards. Your periods, and fertility, will usually take a few months to return after stopping Depo-Provera injections. Sometimes it can take more than a year for your periods and fertility to get back to normal. Studies are looking at whether using Depo-Provera for a long time affects oestrogen levels, as this may increase osteoporosis.
Research is conflicting.
Contraceptive injections do not protect you against sexually transmitted infections, so you may have to use condoms as well.