The contraceptive injection (also called Depo) is an injection of the hormone progestogen. Progestogen is similar to the hormone produced by the ovaries. The contraceptive injection is sold as Depo-Provera or Depo-Ralovera in Australia.

Photo of contraceptive injection vile and needle
Each injection is more than 99% effective at preventing pregnancy and lasts for 12 – 14 weeks. If you have a late injection, it might only be 96% effective.
The injection works by preventing the ovaries from releasing an egg each month.
Illustration of eggs not being released by ovaries
It also thickens the fluid around the cervix (opening to the uterus/womb). This helps to prevent sperm from entering.
Illustration of mucus in cervix
Depo is injected by a doctor or nurse into the arm or bottom muscle every 12-14 weeks.
Illustration of person receiving contraceptive injection
When Depo is first injected, or after a break, it can take up to 7 days to start working to prevent pregnancy. This depends on the timing of your menstrual cycle and if you are already using contraception. Speak with your doctor, nurse or pharmacist for more information.
Your doctor or nurse will provide a script which you can take to the pharmacy, who will sell you the Depo. You will need to return to the clinic to have the Depo injected. It will be cheaper if you have a healthcare card.
The injection might not work if you are late having your injection.
Other possible side effects for a small number of users can include:
These side effects often settle with time.
Rarely the implant is inserted too deep and you may need a surgical procedure to have it removed.
If you do not want to become pregnant and it is more than 14 weeks since your last injection, you can abstain from sex or use condoms until you can have your next injection. It can take up to 7 days for Depo to start working to prevent pregnancy.
During this time, you can continue to abstain from sex or use condoms. If you have unprotected sex in the time when your Depo is late or not effective, you might need emergency contraception.
The injection is not known to harm a pregnancy. It is safe to continue the pregnancy or to have an abortion.
Generally, the injection can be administered straight after you give birth, even if you are breastfeeding. Speak to your doctor or nurse for more information.
You can stop the injection at any time. It may take several months for your fertility to return.
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Last updated: 28 May 2021
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