The contraceptive Injection Is a progestin-containing injection injected by a nurse or health care practitioner every 3 months for pregnancy prevention.    Depending on the injection, you might need to go get another in one, two, or three months (your health care practitioner would let you know this), it is effective, hormonal, and has side effects like light, short or irregular periods, spotting, bleeding, and might take some time for you to get pregnant when you stop.