Wot Wud U Do?
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An injection that releases hormones into your bloodstream to prevent pregnancy and lasts forĀ 8 or 13 weeks, depending on the type.

How effective are they?

Perfect use: more than 99% effective. Fewer than 1 in 100 women will get pregnant in a year when using contraceptive injections regularly.

Typical use: around 94% effective. Around 6 in 100 women will get pregnant in a year.

What are the advantages?

  • It may reduce heavy, painful periods and help with premenstrual symptoms for some women,
  • Once injected you have to remember to keep taking contraception,
  • Not affected by other medicines,
  • Doesn’t interrupt sex.

What makes them less effective to the disadvantages?

  • Side effects can include weight gain, headaches, breast tenderness, irregular bleeding, hair loss, decreased sex drive and mood swings,
  • It can take up to 1 year for your fertility to return to normal after the injection wears off,
  • Your periods may become more irregular, heavier, shorter, lighter or stop altogether,
  • Side effects may continue for as long as the injection lasts and for some time after,
  • Can take 7 days to work.


  • Could cause thinning of bones but the bone replaces itself when you stop the injection,
  • Doesn't protect against sexually transmitted infections,
  • Small risk of infection at the site of injection.

You should talk to your doctor or health professional about risk factors such as smoking, your age or medical history before you have the injection.