Injectable Contraception

What is injectable contraception?

Injectable contraception is a form of contraception that is injected into a muscle (either the upper arm or buttock) to stop pregnancy by releasing progestogen (this is similar to a natural hormone produce by the body). It’s often referred to as Depo.


How does it work?

Progestogen works by:

  • stopping the release of an egg by the ovary (ovulation)
  • making the mucus (sticky fluid) at the opening of the uterus thicker so sperm can’t get through.


How effective is it?

It’s a very effective method of contraception. It is 99.8% effective with perfect use but with typical day-to-day use is about 94% effective.


Where do I get the injection?

You need to make an appointment with your local doctor, SHINE SA or community health clinic to discuss whether this method is a good choice for you.


When can it be given?

It is safe to be given at any time. The chance of pregnancy should be assessed before starting.


When does it start working?

It’s immediately effective when injected:

  • during the first 5 days of your menstrual cycle where day one is the first day of your period
  • while covered by other forms of hormonal contraception (e.g. the Pill, Implant etc.)
  • up to 5 days after having an abortion or miscarriage
  • up to 21 days after having a baby, even if you are breastfeeding.

The injection is not effective until after 7 days if it is given at any other time. Other contraceptive measures such as condoms should be used for these 7 days.


How long does it last?

It is effective as a contraceptive for 12 weeks. It needs to be given regularly every 12 weeks for it to work. If you are late in getting your next injection you may be at risk of pregnancy if you have unprotected sex. You should use condoms until you get the next injection.


When will I be fertile again?

There can be a delay in the return of your fertility and periods with the injection. This can take several months but remember you can get pregnant before your period returns, so continue to use other contraception as needed. Most people will be fertile within 6–12 months from the last injection and there is no permanent effect on fertility.


What are the benefits of the contraceptive injection?

  • It can be used by most people.
  • It can reduce bleeding and painful periods.
  • It doesn’t interact with any other medication.
  • It can’t be seen by other people.


What are the side effects?

Bleeding patterns

Most people will experience a change in bleeding patterns. With continued use the majority of people stop having periods. Some people have irregular bleeding or spotting or continuous bleeding.

Weight gain

Weight gain may occur with the injection.

Headaches, breast pain and mood changes

These symptoms can occur. They usually go away after the first few weeks, but if they persist speak with your doctor or SHINE SA.

Bone health

There is a small drop in your bone density. This is not thought to be harmful for most people, as your bone density returns once you stop the injections.


Who could use injectable contraception?

Injectable contraception is suitable for people who:

  • want a safe and very effective method of avoiding pregnancy and don’t mind having a regular injection
  • don’t mind not having a regular period
  • are unable to use the Pill or vaginal ring because they have problems taking the hormone oestrogen
  • find it difficult to remember to take a daily pill
  • are breastfeeding.


Who should not use the injection?

The injection should not be used by people who:

  • want to get pregnant in the near future
  • have unexplained vaginal bleeding
  • have severe liver disease
  • have current or past breast cancer
  • have a number of risk factors for heart disease (e.g. smoking, diabetes, previous heart attack or stroke).