Intrauterine system (IUS or 'Mirena')

The IUS is a small piece of T-shaped plastic which is fitted into the uterus. It can prevent pregnancy for up to 5 years and is more than 99% effective.

The IUS is a little bit like the IUD (or the 'coil'), except the IUS has hormones in it. More information on the IUD can be found by clicking here.

Spend a bit of time looking here and finding out more about the IUS and if you have any more questions, call Ask Brook on 0808 802 1234. Your call will be confidential. That means we won't tell anyone about it.

The IUS is one of the types of contraception called a LARC. LARC stands for 'Long Acting Reversible Contraception'. LARC methods don't rely on you remembering to take them, but they do need a professional (like a doctor or a nurse) to give them to you. They are very effective.

How does the IUS work?
How do you use the IUS?
What's Good about the IUS?
Things to watch out for with the IUS
How effective is the IUS?
What makes the IUS less effective?
Who can use the IUS?

How does the IUS work?

The IUS works by stopping sperm meeting an egg or may stop an egg implanting in the womb. In some cases, it can stop ovulation (stop an egg being released).

How do you use the IUS?

The IUS is put into the uterus through the vagina. It can only be fitted by a trained doctor or nurse. It usually takes about 15-20 minutes and may hurt a bit, although this shouldn't last for long. You may want to use a local anaesthetic and you should be given painkillers to help. Your doctor or nurse should talk to you about the pain beforehand. You may also get some period-type pain and possibly some light bleeding for a few days afterwards.

You can go to a contraceptive clinic, a young people's service or a Brook centre to get your IUS fitted. Some GPs also fit the IUS, but not all. You may want to ring ahead, before you go, to check that someone that can fit an IUS is available.

Once the IUS is fitted, you will need to go back for a check up three to six weeks later.

If the IUS is fitted in the first seven days after your period starts it works straight away.  If it is fitted at any other time you will need to use another form of contraception for seven days..

What's good about the IUS?

• It does not interrupt sex.
• Once you have had it fitted, it prevents pregnancy for five years.
• Your periods may be lighter.
• It's not affected by other medicines.
• Your fertility will return to normal after the IUS has been removed.

What do I need to watch out for with the IUS?

• It does not protect against sexually transmitted infections (STIs).
• It can cause irregular bleeding at first.
• It can cause temporary side effects such as skin problems or breast tenderness.

How effective is the IUS?

The IUS is more than 99% effective. This means that less than 1 in every 100 women who use an IUS will get pregnant each year.

What makes the IUS less effective?

If the IUS moves out of place it will be less effective. You will need to go back 3 to 6 weeks after it has been fitted so your health practitioner can check the IUS is in place. The doctor or nurse will teach you how to check that it is in place after this and you should check yourself once a month.

Who can use the IUS?

The IUS is suitable for most women. A doctor or nurse will need to know about a woman's medical history and any illnesses suffered by immediate members of her family. That's to find out if there are any medical reasons why it might not be suitable for you.