What Is the Birth Control Shot? The birth control shot is an injection given to a girl every 3 months to help prevent pregnancy. The birth control shot contains a long acting form of the hormone progestin. How Does the Birth Control Shot Work? The hormone progestin in the birth control shot works by preventing ovulation (the release of an egg during the monthly cycle). If a girl doesn't ovulate, she cannot get pregnant because there is no egg to be fertilized. The progestin also thickens the mucus around the cervix. This makes it hard for sperm to enter the uterus and reach any eggs that may have been released. The progestin also thins the lining of the uterus so that an egg will have a hard time attaching to the wall of the uterus. How Well Does the Birth Control Shot Work? The birth control shot is an effective birth control method. Over the course of a year, about 6 out of 100 typical couples who use the birth control shot will have an accidental pregnancy. The chance of getting pregnant increases if a girl waits longer than 3 months to get her next shot. In general, how well each type of birth control method works depends on a lot of things. These include whether a person has any health conditions or is taking any medicines that might affect its use. It also depends on whether the method is convenient and whether the person remembers to use it correctly all of the time. Does the Birth Control Shot Help Prevent STDs? No. The birth control shot does not protect against STDs. In fact, some studies show that the birth control shot may possibly increase the risk of getting certain STDs, although scientists do not understand why. Couples having sex must always use condoms along with the shot to protect against STDs. Are There Any Side Effects With the Birth Control Shot? Many girls who use the birth control shot will notice a change in their periods. Side effects that some girls have include: irregular periods or no menstrual periods weight gain, headaches, and breast tenderness depression The U.S. Food and Drug Administration (FDA) has issued a safety warning about the use of the birth control shot. Studies link this shot to a loss of bone density in women, although bone density may recover when a woman is no longer getting the shot. The loss of bone density seems to be worse when the shot is used for longer periods of time. Doctors are not sure how this type of shot may affect the bone density of teen girls in the future, though. Girls who are considering the shot should talk to their doctors about it and make sure that they get enough calcium each day. Those who smoke should be sure to let their doctors know because smoking may be connected to this bone density loss. Women may notice a decrease in fertility for up to a year after they stop getting the birth control shot. However, the shot does not cause permanent loss of fertility and most women can get pregnant after they stop getting the shot. Who Can Use the Birth Control Shot? Girls who have trouble remembering to take birth control pills and who want extremely good protection against pregnancy may want to use the birth control shot. Also, nursing mothers can use the birth control shot. Not all girls can — or should — use the birth control shot. Some medical conditions make the use of the shot less effective or more risky. For example, it is not recommended for girls who have had blood clots, some types of cancers, or liver disease. Girls who have had unexplained vaginal bleeding (bleeding that is not during their periods) or who suspect they may be pregnant should not get the birth control shot and should talk to their doctors. Where Is the Birth Control Shot Available? The shot must be prescribed and is given every 3 months in a doctor's office or family planning clinic. How Much Does the Birth Control Shot Cost? Each injection (3 months' worth of birth control) costs between $0 and about $150. Many health insurance plans cover the cost of birth control shots, as well as the cost of the doctor's visit. Family planning clinics (such as Planned Parenthood) may charge less. When Should I Call the Doctor? If you use the birth control shot, call your doctor if you: might be pregnant have a change in the smell or color of your vaginal discharge have unexplained fever or chills have belly or pelvic pain have pain during sex have heavy or long-lasting vaginal bleeding have yellowing of the skin or eyes have severe headaches feels depressed have signs of a blood clot, such as lower leg pain, chest pain, trouble breathing, weakness, tingling, trouble speaking, or vision problems Back to Articles Related Articles Abstinence Abstinence is the only form of birth control that is 100% effective in preventing pregnancy. Abstinence also protects people against STDs. Read More Birth Control Methods: How Well Do They Work? Some birth control methods work better than others. This chart compares how well different birth control methods work. Read More STDs (Sexually Transmitted Diseases) You've probably heard lots of discouraging news about sexually transmitted diseases. The good news is that STDs can be prevented. Find out how to protect yourself. Read More Gyn Checkups Girls should get their first gynecological checkup between ages 13 and 15. Find out what happens during a yearly gyn visit -- and why most girls don't get internal exams. Read More About Birth Control Before you consider having sex, you need to know how to protect yourself. Read this article to get the basics on birth control. Read More When Is it Time to Start Seeing a Gynecologist? Find out what the experts have to say. Read More Female Reproductive System Why do girls get periods? What goes on when a woman gets pregnant? What can go wrong with the female reproductive system? Find the answers to these questions and more in this article for teens. Read More Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor. © 1995-2021 KidsHealth®. All rights reserved. Images provided by The Nemours Foundation, iStock, Getty Images, Veer, Shutterstock, and Clipart.com.