The contraceptive injection is a long-acting contraception containing the hormone progestogen, providing protection against pregnancy for 12 weeks at a time.

The hormone is injected into a muscle, usually your bottom.

How does it work?

It works by thickening cervical mucous to prevent sperm from being able to reach an egg, and by thinning the lining of the womb so that if an egg was fertilised it would not be able to implant. In some women, the injection will stop eggs from being released (ovulation).

How effective is it?

The contraceptive injection is over 99 per cent effective in preventing pregnancy.

What are the advantages?

You only have to remember to take it once every 12 weeks and it does not interrupt sex.

Other benefits are lighter or no periods, reduced period pain and less premenstrual symptoms. Research also suggests that it provides some protection against womb cancer and pelvic inflammatory disease.

What are the downsides?

Using the contraceptive injection can disrupt your periods, cause irregular bleeding, and for some women cause periods to be heavier and longer. Other side effects include headaches, mood changes, weight gain, spotty skin and breast tenderness.

Also, in the short-term, once you have stopped using the injection it may take some months for your periods and fertility to return to normal. The contraceptive injection can also cause your bones to thin, which may be problematic for women with osteoporosis.

Things to bear in mind:

The contraceptive injection may not be suitable for women aged below 19, because bone development is still taking place during your teenage years. You will be counselled about the risks of osteoporosis before you are prescribed the medication

The injection is not reversible, so if you have side effects you will not be able to stop them until the injection has worn off after 12 weeks.

Most importantly, the contraceptive injection does not provide any protection against HIV or other sexually transmitted infections like a condom does.

Where can I get it from and how much does it cost?

The contraceptive injection is available free on the NHS. You can only get it on prescription. This can be from your GP, another GP who you have registered with for family planning services, a practice nurse or a family planning or young person’s clinic.

Page content supplied by Copyright 2012 © Terrence Higgins Trust.

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