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Contraceptive Injection

The contraceptive injection contains a hormone which is injected into your upper arm or buttocks.


How does it work?

The contraceptive injection works by releasing the hormone progesterone.

The contraceptive injection prevents ovulation.

This is when the ovaries release an egg each month.

Progestin thickens the mucus in the cervix so sperm cannot easily pass through and it thins the lining of the womb (endometrium) which makes it difficult for the egg to implant itself.


How long does it last?

The contraceptive injection lasts for around 2-3 months (8-13 weeks) depending on the brand.

Who can use it?

The majority of women are able to have the contraceptive injection.

It may not be suitable if you*:


  • Have a history of breast cancer

  • Have a history of blood clots

  • Have a history of liver disease

  • Are at risk of osteoporosis

  • You are pregnant or trying to conceive soon

How effective is it?

The contraceptive injection is approximately 99% effective when used perfectly but 94% effective with typical use


There are many advantages to using the contraceptive injection such as:


  • It is long-lasting

  • It can be used when breastfeeding

  •  It can help improve painful or heavy periods

  • It is an alternative to oestrogen contraceptives

  • It is unlikely to interact with other medications


The disadvantages of the contraceptive injection include:


  • Lack of prevention against STIs

  • Regular injections

  • Your periods may not return to normal for up to 12 months after stopping the injection

  • There are risks (e.g. infection, allergic reaction, bone thinning)

  • Side effects (e.g. acne, headaches, reduced sex drive (libido), mood changes and hair loss)

*This is not an extensive list. Please see your doctor for further advice.

Sources and Useful links
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