Hormonal coil (IUS)

Mirena coil

What the packet says

What is Mirena coil?

Hormonal ingredients

What's it made of?

The Mirena coil (IUS) is made of a small white T-shaped frame made from a plastic called polyethylene. The hormone is contained within a silicone substance called polydimethylsiloxane, which is surrounded by a membrane (skin) also made of polydimethylsiloxane. The T-shaped frame also contains barium sulphate so that it can be seen on X-rays. There are two fine brown threads, made of iron oxide and polyethylene, attached to the bottom of the frame.

How Mirena coil works

The hormonal coil or IUS is a small, T-shaped plastic device that is inserted into your womb by a doctor or nurse. It releases the hormone progestogen gradually into your womb which prevents pregnancy by making the fluid in your cervix thicker (which makes it more difficult for sperm to enter the womb) and preventing the lining of your womb thickening enough for an embryo to grow in it. Sometimes it can also stop you ovulating.

Mirena coil side effects

  • Womb Cramps
  • Tender Breasts
  • Vaginal Discharge
  • Spots or acne
  • Headaches


  • During intercourse
  • Daily
  • Monthly
  • 1 - 3 Months
  • 1 - 3 Years
  • 3 - 5 Years
  • Permanent
  • Similar to

    Clinical effectiveness



    Contains hormones


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    Detailed information

    How to get started with the Mirena coil

    Women ask us lots of questions about getting an IUS / hormonal coil fitted – so we’ve put together a guide on everything you ever wanted to know about the coil. Below are a few key points to consider:

    • To get a contraceptive coil fitted you need to go to a GP surgery or sexual health clinic where some staff are trained to fit them. You can contact your GP and ask if they fit coils, or search for clinics that fit coils here.
    • The Mirena coil can be fitted at any time during your monthly period cycle, as long as you’re not pregnant (although you may prefer to get it fitted when you’re not on your period).
    • Your doctor or nurse will do some tests to make sure that you can have the coil – like making sure that you’re not pregnant and checking for infections or STIs.
    • Your doctor or nurse will use a speculum (like when you have a smear test) to open up your vagina and then insert the coil through the cervix into the womb. Most women find this uncomfortable.
    • If it’s fitted in the first seven days of your cycle, you’ll be protected against pregnancy straight away. If it’s fitted at any other time, you’ll need to use condoms or other contraception, for seven days afterwards.
    • You will normally go back for a check up 3-6 weeks after getting it fitted.

    How to stop the Mirena coil

    • Mirena coil removal can happen at any time by a trained doctor or nurse. It’s simpler than having it fitted – they will gently pull on the threads and the T shape folds up and it can be pulled out of the womb.
    • If you’re not having another coil put in and don’t want to get pregnant, you’ll need to make sure you don’t have sex seven days before you have it removed, or use condoms or another method.
    • Check out our survey results to read Mirena coil reviews and see how long it took most women’s cycles to return to their definition of ‘normal’ and read up about other after effects they’ve experienced.

    Things that can go wrong

    • There’s a small risk of infection after the Mirena coil been fitted. This may occur when harmless bacteria normally found in vagina are pushed inside the womb. You’ll know it’s infected if you have unusual discharge, there’s a strong smell, or you develop a high temperature or chills.
    • Around 1 in 20 contraceptive coils can fall out or be pushed out by the womb, this is most common in the first few weeks of getting it fitted, or during a period. If this happens, head to your doctor or nurse to get a check up.
    • If the coil doesn’t work and you get pregnant, there’s also a small increased risk of ectopic pregnancy – when the egg implants outside the womb, normally the fallopian tubes. However, the overall risk of ectopic pregnancy is less in women using a coil than in women using no contraception at all.
    • Very occasionally the threads get lost. This happens to about 1 in 100 women, and is more commonly caused by the threads being pulled up inside into the cervix. They may notice this when you go to have the coil removed, and sometimes the threads can reappear naturally.
    • Even more occasionally (1 in 1000 chance) the coil goes through the wall of the womb into the abdomen. This is called ‘perforation’ and it this happens, they can remove the coil via surgery.


    Hormonal coil (IUS)


    Was under general for insertion, so did not feel it. Chronic migraines and endometriosis were already problems. Thought ...
    Hormonal coil (IUS)


    Hormonal coil (IUS)


    The fitting was horrendous. Took 2 appointments, many different sizes of speculum because the (experienced) fitter could...
    Hormonal coil (IUS)


    Pro: not having to remember to take pill, lighter periods and less often. Better moods. Con: painful insertion, abdomina...
    Hormonal coil (IUS)


    I’ve recently had my second Mirena coil fit, as although it’s not perfect it is the best contraceptive I’ve found ...
    Hormonal coil (IUS)


    I was on Mirena for around 18 months and never had a problem. After 18 months, and presumably after a cervical screening...