Birth Control Hormones: The Shot

Topic Overview

What is the shot?

The shot is used to prevent pregnancy. You get the shot in your upper arm or rear end (buttocks). The shot gives you a dose of the hormone progestin. The shot is often called by its brand name, Depo-Provera.

Progestin prevents pregnancy in these ways: It thickens the mucus in the cervix. This makes it hard for sperm to travel into the uterus. It also thins the lining of the uterus, which makes it harder for a fertilized egg to attach to the uterus. Progestin can sometimes stop the ovaries from releasing an egg each month (ovulation).

The shot provides birth control for 3 months at a time. You then need another shot.

The shot can cause bone loss. Most women can use it safely for up to 2 years and then may choose to switch to another form of birth control. Some women may be able to use the shot for more than 2 years.

How well does it work?

In the first year of use:^{footnote 1}

• When the shot is used exactly as directed, fewer than 1 woman out of 100 has an unplanned pregnancy.
• When the shot is not used exactly as directed, 6 women out of 100 have an unplanned pregnancy.

Be sure to tell your doctor about any health problems you have or medicines you take. He or she can help you choose the birth control method that is right for you.

What are the advantages of the shot?

• The shot is one of the most effective methods of birth control.
• It's convenient. You need to get a shot only once every 3 months to prevent pregnancy. You don't have to interrupt sex to protect against pregnancy.
• It prevents pregnancy for 3 months at a time. You don't have to worry about birth control for this time.
• It's safe to use while breastfeeding.
• The shot may reduce heavy bleeding and cramping.
• The shot doesn't contain estrogen. So you can use it if you don't want to take estrogen or can't take estrogen because you have certain health problems or concerns.

What are the disadvantages of the shot?

• The shot doesn't protect against sexually transmitted infections (STIs), such as herpes or HIV/AIDS. If you aren't sure if your sex partner might have an STI, use a condom to protect against disease.
• The shot may cause bone loss in some women. You shouldn't use this method for more than 2 years without talking to your doctor first about the risks and benefits.
• Any side effects may last up to 3 months.
  • The shot may cause irregular periods, or you may have spotting between periods. You may also stop getting a period. Some women see having no period as an advantage.
  • It may cause mood changes, less interest in sex, or weight gain.
• You must go to the doctor every 3 months to get the shot.
• If you want to get pregnant, it may take 9 to 10 months after you stop getting the shot. This is because the hormones the shot provided have to leave your system, and your body has to readjust.
• If you have severe side effects, you have to wait for the hormones to get out of your system. This may take up to 3 months.