Injectable contraception

The injectable contraception contains an artificial form of the progesterone hormone.

It is:

  • Over 99% effective when you use the method correctly every time
  • Over 94% effective when you don’t always use the method correctly

What is it?

An injection of an artificial form of the hormone progesterone is injected into your arm or bum.

How does it work?

Progestogen is slowly absorbed from the muscle into the blood over a course of 12 weeks.

It works by:

  • stopping ovulation (an egg being released from your ovaries)
  • thickening the mucus at the neck of the womb (uterus) so that it is difficult for sperm to enter the womb
  • thinning the lining of the womb and this prevents a fertilised egg from settling (implanting) in the womb

It is important that you talk to a doctor who will assess what contraceptive option is best for you.


  • It works for up to 12 weeks and you don't have to think about contraception during this time.
  • It does not interrupt sex.
  • It is useful if you are likely to forget to take the pill daily.
  • It is suitable for women over 35 who smoke.


  • It cannot be removed from the body so side effects may continue while it works and for some time afterwards. 
  • It can take 6 to 12 months for periods and fertility to return to normal.
  • Does not protect against sexually transmitted infections.