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A woman getting an injection

Contraceptive Injections

Getting the contraceptive jab


Written by SpunOut | View this authors Twitter page and posted in health


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Contraceptive injections do NOT protect against sexually transmitted infections. They are 99% effective in preventing prengancy when used regularly.

This is an injection that releases the hormone progestogen into your body.

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.

Advantages of the injection

  • It is a very effective contraception. Many of the unplanned pregnancies that occur on the injection are due to the woman forgetting or delaying her repeat injection.
  • The injection offers some protection against womb cancer.
  • Useful for women who forget to take their pill 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.
  • You don’t need to worry about remembering to take it every day or to use it during sex.

Disadvantages of the injection

  • The injection does not protect against sexually transmitted infections.
  • You have to remember to have the injection on time every three months.
  • Your periods can become irregular or stop. You might have bleeding between periods. In general, most women experience some changes in their periods while on the injection.
  • The injection may cause bone loss, particularly in young women.
  • Injection must be given by a doctor or a nurse.
  • Cannot be immediately reversed in the event of side effects
  • Can take time for regular periods and fertility to return to normal.
  • It may take up to a year for your periods to return.
  • There might be other side effects such as weight gain, headaches, dizziness, acne, breast swelling, stomach pain, hair loss and reduced sex drive.

How to use 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.

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.

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Published February 6th, 2013
Last updated October 29th, 2015
Tags contraception sexual health sex
Can this be improved? Contact editor@spunout.ie if you have any suggestions for this article.

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