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Contraceptive Injections

What is it and how does it work?

The contraceptive injection contains a hormone called progestogen and is a long-term method of contraception. It's injected into a muscle and the hormone is released very slowly into the body. There are two types of injection:

  • Depo-Provera provides contraceptive protection for three months (12 weeks).

  • Noristerate provides contraceptive protection for two months (eight weeks). Contraceptive injections are more than 99 per cent effective. This means that using this method, fewer than one woman in 100 will get pregnant in a year. The hormone is injected into a muscle in your bottom. It's usually given during the first five days of a period when it provides immediate contraceptive protection. If given on any other day, an extra method of contraception must be used for seven days. The injection works by:

  • stopping the ovaries releasing an egg each month

  • stopping sperm reaching the egg by thickening the mucus from the cervix

  • stopping the egg settling in the womb


  • It's highly effective.

  • It doesn't interfere with sex.

  • The injection provides some protection against both cancer of the womb and pelvic inflammatory disease.

  • It can be used by women who are breastfeeding.

  • You don't have to think about contraception for as long as it works.


  • The injection can cause irregular bleeding or longer periods. Some women find their periods stop completely, while others have frequent, light bleeding. Irregular bleeding can continue for some months after stopping the injections.

  • Some women experience side effects including weight increase, headaches, acne, breast tenderness, mood swings and bloating.

  • The injection cannot be removed from the body. If side effects occur, they'll last as long as the injection does and sometimes longer.

  • Your fertility and periods can take a while to get back to normal after stopping Depo-Provera.

Can anyone use the contraceptive injection?

Contraceptive injections don't suit everyone. Reasons not to use them include:

  • you think you might be pregnant

  • you don't want any changes to your periods You also shouldn't use this method if you have now, or have had in the past:

  • cancer of your reproductive organs, for example breast or womb cancer

  • unexplained bleeding from the vagina

  • a heart attack or stroke

  • severe depression

  • active liver disease

General comments

Contraceptive injections can be less effective if you don't have the next one on time.

Depo-Provera and affects on bone density and growth Women who use Depo-Provera have been shown to have lower bone mineral density than women who don't use it. It is not known if this effect increases the risk of osteoporosis and fractures in later life. Because of this all women, especially young women under 19 should be informed of all other contraceptive choices.

Where to get it

Contraception is free at State health services. Your GP or family planning clinic can provide contraceptive injections.

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