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Injection – for contraception – What do I need to know?

The contraceptive injection contains a hormone called a progestogen.

There are three different contraceptive injections available in the UK:

  • Medroxyprogesterone acetate which is given as an injection into the buttock every 12-13 weeks. It is also known as Depo Provera.  This is the form of injectable contraception that is most commonly used.  We use Depo-Provera in Unity Sexual Health.
  • Medroxyprogesterone acetate which is available as an injection that you can give yourself every 13 weeks. It is also known as Sayana Press.  We do not supply Sayana Press in Unity.
  • Norethisterone enantate which is given as an injection into the buttock every 8 weeks. It is also known as Noristerat.  This is not commonly used.

Depo-Provera will protect you from pregnancy for 13 weeks.  It is over 99% effective as a method of contraception.

Depo-Provera is one of the LARCs.  A LARC is a Long Acting Reversible Contraceptive method.  All LARCs are very effective because you do not have to remember them every day.

How does the contraceptive injection work?

It works in three ways:

  • Stopping ovulation.  Ovulation is when your ovaries release an egg each month.
  • Thickening the mucus that comes from your cervix to prevent sperm from entering.
  • Making the lining of your womb thinner.

The  injection is given into a muscle, usually your buttock.

You can access a good leaflet telling you all about contraceptive injections here:

What are the advantages of the contraceptive injection?

  • You don’t have to think about contraception for as long as the injection lasts.
  • You can use it if you are breast feeding.
  • It is not affected by other medications.
  • It may help with heavy, painful periods and premenstrual symptoms.
  • It is a good method if you are not able to use estrogens, like those in the combined hormonal contraceptive pill.

What are the disadvantages of the contraceptive injection?

  • Your periods may change.  Many women don’t have any periods when using contraceptive injections.  Some women may have irregular but light periods.  Other women may have heavy or longer periods.
  • Irregular bleeding may continue for some months after you stop the contraceptive injection.
  • Some women put on weight.
  • The contraceptive injection cannot be removed from your body.  If you do have any side effects they may continue whilst the contraceptive injection is active and for some time afterward.
  • There can be a delay of up to one year before the return of your periods and fertility after stopping the contraceptive injection.
  • Some women experience side effects such as spotty skin, hair loss, decreased libido, mood swings and headaches.

Are there any risks with the contraceptive injection?

  • The contraceptive injection may reduce the density of your bones.  For the majority of women this is not a problem but if you have risk factors for brittle bones or osteoporosis you may wish to avoid this method. If you are worried about this then please discuss with the doctor or nurse you see about contraception. For information about risk factors for osteoporosis please visit the National Osteoporosis Society website.
  • Some research suggests there may be a slightly higher risk of breast cancer with all hormonal methods of contraception.
  • There is a small chance you will be allergic.
  • There is a small risk of infection at the injection site.

For more information about the advantages, disadvantages and risks of the contraceptive injection you may want to read this leaflet:

How often do I need to have the contraceptive injection?

You should have your Depo-Provera injection every 13 weeks.

You can have it slightly early if you are experiencing bleeding which is causing you a problem or you are going on holiday.

You can start the contraceptive injection:

  • at any time in your cycle as long as you are certain that you are not pregnant – the method will take 7 days before it is effective.
  • during the first 5 days of your period – then the method will be effective immediately.

Where can I get the contraceptive injection from?

You can get a Depo-Provera injection from your GP or one of the Unity Sexual Health clinics.

What happens if I miss my contraceptive injection?

If you miss your Depo-Provera injection and you do not want to be pregnancy you should:

  • Abstain from any sexual contact or use condoms or femidoms every time you have sexual contact.
  • Make an appointment to see your GP, Unity Sexual Health, or one of our partners as soon as possible.

If you have any unprotected sexual contact after your Depo-Provera has run out then you may need emergency contraception.

If you think that you might need emergency contraception then it is important that you get advice as quickly as possible.  There are time limits on when you can take emergency contraception.

Further information on Emergency Contraception on our website.

You can also access an FPA information leaflet about emergency contraception here:

If you want to talk to someone about emergency contraception you can speak to you GP or one of the Unity Sexual Health clinics.

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