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Contraceptive injection

A woman can get pregnant if a man’s sperm reaches one of her eggs (ova). Contraception tries to stop this happening by keeping the egg and sperm apart or by stopping egg production. One method of contraception is the injection.

We have included further information about the injection below to help you make an informed choice about your contraception. After reading it, if you think the injection is the right contraception choice for you, you need to make an appointment to come to our clinic.

About the injection

  • If used correctly, the contraceptive injection is more than 99% effective. This means that less than one woman in 100 who use the injection will become pregnant in a year
  • The injection lasts for eight or 12-14 weeks (depending on the type), so you don't have to think about contraception every day or every time you have sex
  • It can be useful for women who might forget to take the contraceptive pill every day
  • It can be useful for women who can't use contraception that contains oestrogen
  • It's not affected by medication
  • The contraceptive injection may provide some protection against cancer of the womb and pelvic inflammatory disease
  • Side effects can include weight gain, headaches, mood swings, breast tenderness and irregular bleeding. The injection can't be removed from your body, so if you have side effects they'll last as long as the injection and for some time afterwards
  • Your periods may become more irregular or longer, or stop altogether (amenorrhoea). Treatment is available if your bleeding is heavy or longer than normal – talk to your doctor or nurse about this
  • It can take up to one year for your fertility to return to normal after the injection wears off, so it may not be suitable if you want to have a baby in the near future
  • Using Depo-Provera affects your natural oestrogen levels, which can cause thinning of the bones
  • The injection does not protect against sexually transmitted infections (STIs). By using condoms as well as the injection, you'll help to protect yourself against STIs

How the injection works

The contraceptive injection, Depo-Provera, is usually given into a muscle in your bottom, although sometimes it may be given in a muscle in your upper arm.

If you have the injection during the first five days of your cycle, you will be immediately protected against becoming pregnant.  If you have the injection on any other day of your cycle, you will not be protected against pregnancy for up to seven days. Use condoms or another method of contraception during this time.

Download the Family Planning Association guide to contraceptive injections.