Birth Control Hormones: The Shot

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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 may cause bone loss. Talk to your doctor about the risks and benefits.

How well does it work?

When the shot is used exactly as directed, it is more than 99% effective for preventing pregnancy. That means that fewer than 1 out of 100 people who use it will have an unplanned pregnancy. But when the shot is not used exactly as directed, it is about 94% effective. This means that about 6 out of 100 people who use it will have an unplanned pregnancy.footnote 1

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

What are the advantages of using the birth control 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 using the birth control shot?

  • The shot doesn't protect against sexually transmitted infections (STIs), such as herpes or HIV. A condom can be used to reduce your risk of getting an STI.
  • The shot may cause bone loss in some people. Talk to your doctor about the risks and benefits.
  • The shot is needed every 3 months. Any side effects may last 3 months or longer.
    • The shot may cause irregular periods, or you may have spotting between periods.
    • It may cause mood changes, less interest in sex, or weight gain.
  • If you want to get pregnant, it may take up to a year 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.



  1. Trussell J (2011). Contraceptive failure in the United States. Contraception, 83(5): 397–404. DOI: 10.1016/j.contraception.2011.01.021. Accessed December 8, 2022.


Current as of: November 27, 2023

Author: Healthwise Staff
Clinical Review Board
All Healthwise education is reviewed by a team that includes physicians, nurses, advanced practitioners, registered dieticians, and other healthcare professionals.

The Health Encyclopedia contains general health information. Not all treatments or services described are covered benefits for Kaiser Permanente members or offered as services by Kaiser Permanente. For a list of covered benefits, please refer to your Evidence of Coverage or Summary Plan Description. For recommended treatments, please consult with your health care provider.