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IUS (intrauterine system)

The IUS is a small, T-shaped plastic device, which contains the hormone progestogen to control your fertility. The device is put into the uterus (womb) through the vagina by a specially trained doctor or nurse.

The IUS is like the IUD, except the IUS has hormones in it (the IUD doesn’t). 

Here are some key facts:

  • The IUS is over 99% effective
  • It works for up to three or five years depending on the brand of IUS
  • The IUS is a method of long-acting reversible contraception (or LARC) - these methods don’t rely on you remembering to take them
  • It can help with heavy or painful periods
  • Your fertility returns to normal as soon as the IUS is removed
  • It doesn't protect against sexually transmitted infections (STIs) so you'll need to use condoms as well

How does the IUS work?

Pregnancy happens when sperm reaches an egg and fertilises it. The IUS works in three ways to interrupt this process:

  • It works by thickening the mucus around the cervix, which makes it harder for sperm to get through and reach an egg
  • It makes the lining of the womb thinner so that a fertilised egg cannot implant
  • In some women it can also stop ovulation (when ovaries release an egg), although most women continue to ovulate. 

The IUS is a long-acting reversible contraception (or LARC) method - these methods don't rely on you remembering to take them, but they do need a trained doctor or nurse to fit them for you.

The IUS is over 99% effective at preventing pregnancy. This means that less than one woman in 100 will get pregnant in a year.

Currently there are four brands of IUS - Mirena, Jaydess, Levosert and Kyleena. Some brands work for five years, some work for three years. Your doctor or nurse will discuss in more detail with you.


How do I get the IUS?

The IUS needs to be fitted by a doctor or nurse who has been specially trained. It is available free from a range of services including contraceptive clinics, your GP and Brook. Find your nearest using our find a service tool.

What will happen at the appointment?

When you go to get the IUS, you will be asked a few questions about your medical and family history, to work out what would suit you best. 

If you decide to go ahead you'll discuss when would a suitable time to have it fitted. Some services may be able to do the fit at the same appointment , or you may need a second appointment.

You will need to have an internal examination (a doctor or nurse will look inside your vagina) to check the position and size of your uterus before the IUS can be fitted, and also to check for any signs of infection, sometimes you may also be given antibiotics when the IUS is fitted.

The appointment usually takes about 15-20 minutes. During the appointment you'll be asked to lay on the bed and remove the lower half of your clothing (e.g. trousers/skirt and underwear). You'll then have to open your legs and bend your knees so the doctor or nurse can use a speculum to slightly widen your vagina to help insert and guide the IUS into your uterus. The fitting itself shouldn't take longer than 5 minutes.

The doctor or nurse may discuss painkiller tablets and/or using local anaesthetic to make the fitting more comfortable.

After the IUS is fitted

You may also get period-type pain and possibly some light bleeding for a few days afterwards.

The IUS has two threads which hang through the opening at the entrance of your uterus (cervix) and the doctor or nurse will teach you to check the threads to make sure the IUS is in place. You should check the threads a few times during the first month and then at regular intervals.

It is very unlikely that the IUS will come out but if you are worried and can feel the IUS itself, or cannot feel the threads you should see a doctor or nurse straight away. You may also not be protected against pregnancy and may need to use additional contraception or emergency contraception.

Once the IUS is fitted, you will need to go back to the doctor or nurse after three to six weeks for a check-up. You will then only need to go back if you have any problems or when the IUS needs to be replaced (three or five years depending on the type of IUS). You can return to the clinic if you are worried.  

When to seek help

You should go back to the or doctor or nurse if you notice any of the below symptoms:

  • Severe or prolonged abdominal pain, especially if you feel unwell, hot and clammy
  • Heavy vaginal bleeding with or without clots

Contraception and sexual health services such as Brook are free and confidential, including for people under the age of 16. Health professionals work to strict guidelines and won’t tell anyone else about your visit unless they believe you're at serious risk of immediate harm. Find out more about Brook’s confidentiality policy.

Starting the IUS and when you are protected from pregnancy

The IUS can be fitted any time in your cycle if it is certain that you are not pregnant. If fitted in the first seven days of your menstrual cycle you will be immediately protected against pregnancy. If it is fitted at any other time, you will need to use an additional method of contraception (such as condoms) for the first seven days. 

If you have a short menstrual cycle, where your period normally comes every 23 days or less, starting the IUS on the seventh day of your period may mean you are not immediately protected (because you might ovulate early in your menstrual cycle). If you think this might be the case, speak with a doctor or nurse about whether you need to use additional contraception.

How is the IUS removed?

The IUS must be removed by a trained doctor or nurse. The procedure should be less painful and quicker than when the IUS was inserted. If you are not going to have another IUS you'll need to use additional contraception, such as condoms, for the seven days before the IUS is taken out if you do not want to become pregnant.

Your fertility should return to normal as soon as the IUS is removed.

Advantages of the IUS

  • It does not interrupt sex
  • Once you have had it fitted, it prevents pregnancy for up to three or five years depending on the brand of IUS
  • Your periods may be lighter, shorter, or they may stop completely
  • It can help with painful or heavy periods
  • Your fertility will return to normal after the IUS has been removed
  • You don’t have to remember to take a pill every day
  • There is no evidence that the IUS causes additional weight gain
  • It can be taken by some women who cannot use contraception that contains oestrogen, such as the combined pill, contraceptive patch and the contraceptive vaginal ring
  • The IUS is not affected by vomiting, diarrhoea or other medicines like some methods of contraception

Disadvantages of the IUS

  • It does not protect against sexually transmitted infections (STIs)
  • It may cause irregular bleeding at first
  • It can cause temporary side effects such as skin problems, headaches or breast tenderness 
  • It can cause small fluid-filled cysts on your ovaries – these usually disappear without treatment and often there are no symptoms
  • There is a small risk of getting an infection after the IUS is inserted
  • There is a small risk of the IUS becoming pushed out or the IUS being displaced
  • There is a very small risk of tearing of the uterus
  • If you do become pregnant while you are using the IUS there is a small risk of ectopic pregnancy

What can make the IUS less effective?

If the IUS moves out of place it will be less effective. You will need to go back three to six weeks after it has been fitted so your doctor or nurse can check the IUS is in place. They will also teach you how to check that it is in place - you should check yourself once a month or at regular intervals.

How will it affect my periods?

Your periods are likely to become lighter, shorter or they may stop altogether. If you do get periods while using the IUS you can use tampons and/or towels.

However it is also important to check that the bleeding is not due to any other cause. It is recommended that you discuss any concerns that you may have with your nurse or doctor. It might be possible to give you additional medication that can help with the bleeding.

Using the IUS after having a baby

The IUS can be used whilst breastfeeding and will not affect your milk supply. It is usually fitted between four to six weeks after you have given birth, although it can be fitted within 48 hours. 

If you are having the IUS fitted from four weeks onwards you will need to use additional contraception from day 21 of giving birth and until the IUS is fitted.

Using the IUS after having an abortion or miscarriage

If you were pregnant for less than 24 weeks an IUS can be fitted immediately after an abortion or miscarriage by a trained doctor or nurse, and you will be protected against pregnancy straight away. If you were pregnant for longer than 24 weeks you may need to wait a few weeks before using the IUS.

Last review date: September 2017
Next review date: September 2019