Contraceptive Injections

Find out if the contraceptive injection is right for you
Written by

Contraceptive injections do not protect against sexually transmitted infections

The contraceptive injection is an injection that releases the hormone progestogen into your body to prevent pregnancy.

The injection works like the pill, but lasts for 12 weeks. It is given in your arm or bum by a GP or nurse. It is usually administered during the first five days of a period and is available on prescription only.

The injection works by preventing ovulation (the release of an egg) and by thickening your cervical mucus so that sperm cannot meet the egg. It also thins the lining of your womb.

Benefits of the contraceptive injection

  • It is a very effective contraception – many of the unplanned pregnancies that occur on the injection are due to the peron forgetting or delaying their repeat injection
  • Unlike the pill, this is not something you need to remember every day
  • If you are vomiting or have diarrhoea, it doesn't affect the contraceptive, unlike the pill
  • Medication doesn't interfere as much with the injection, as it does with the pill
  • There is a lower risk of having an ectopic pregnancy or ovarian cysts while on the injection
  • The injection does not contain oestrogen, which means it does not increase the risk of blood clots or strokes

How to get the contraceptive injection

  • The injection must be given to you by a doctor or nurse.
  • It is usually given as an injection on your bum.
  • If it is given during the first five days of your period, it becomes effective immediately.
  • You must get an injection every three months. If you are late getting your next injection, you may become pregnant. So it is important to put a reminder for your next injection on your phone or on a calendar.

Things to keep in mind with the contraceptive injection

  • The injection does not protect against sexually transmitted infections
  • You have to remember to have the injection on time every three months
  • Most people experience changes in their periods while on the injection, including irregular periods or no periods at all
  • You might have bleeding between periods 
  • Side effects can include weight gain, headaches, dizziness, acne, breast swelling, stomach pain, hair loss and reduced sex drive
  • It can take time for regular periods (up to a year) and fertility to return to normal when you stop the injection
  • The injection can affect your natural oestrogen levels, cause the thinning of the bones – this is not a long term side effect as the bone replaces itself when most people stop the injection

Remember: The age of sexual consent in Ireland is 17. If you're over 16, you can consent to medical treatment including any treatment or tests needed.

Related articles
Skip to content