An IUS is a small plastic device that’s put into your uterus (womb) and releases a progestogen hormone. This is similar to the natural progesterone produced by the ovaries.

The IUS works as contraception for between 3-8 years depending on the type.

There are different types and sizes with different amounts of the progestogen hormone.

If you’re aged over 45 when a particular type of IUS (Mirena or Levosert) is fitted, it’ll work as contraception until after the menopause when contraception isn’t needed.

Patient leaflets

The IUS works in a number of ways.

  • thickening the mucus from your cervix (neck of the womb). This makes it difficult for sperm to move through it and reach an egg.
  • thinning the lining of your uterus (womb) so it’s less likely for a fertilised egg to be able to implant into the womb and create a pregnancy.

In some people, it stops the ovaries releasing an egg (ovulation), but most IUS users continue to ovulate.

An IUS does not cause an abortion.

It’s common for your bleeding pattern to change while you’re using the IUS. 

In the first six months, irregular bleeding or spotting is common.

Periods usually become lighter, shorter and less painful.

Many people find their periods stop altogether. This isn’t harmful.

If you have bleeding that's a problem for you at any time, talk to your healthcare professional. They may be able to give you some additional hormone or medicine that can help control the bleeding. They may also check that the bleeding isn't due to other causes, such as an infection.

Yes, it’s safe to use tampons or a menstrual cup.

Make sure that the menstrual cup is put in the correct place and not too high in the vagina.

Take care not to pull on the IUS threads when you’re removing tampons or a menstrual cup.

The IUS is a method of long-acting reversible contraception (LARC). LARC is very effective because it doesn’t depend on you remembering to take or use contraception.

The IUS is over 99% effective. Less than one IUS user in 100 will get pregnant in one year.

Most people with a uterus (womb) can use an IUS, including those who’ve never been pregnant and young people.

Your doctor or nurse will ask you about your medical history to check if the IUS is suitable. Mention any illness or operations you’ve had as you may need specialist care when the IUS is fitted.

You may be advised not to use an IUS if you:

  • think you might already be pregnant
  • have had a baby in the last four weeks (although it can be inserted immediately after the baby is born)
  • have symptoms of an untreated sexually transmitted infection or pelvic infection
  • have breast cancer or have had it in the past
  • have problems with your uterus (womb) or cervix (neck of the womb)
  • have serious liver disease
  • have unexplained bleeding from your vagina (for example between periods or after sex)
  • have arterial disease or history of serious heart disease or stroke.

You may still be able to use an IUS, even if you have any of the above conditions. Your doctor or nurse will discuss this with you.

You don’t have to remember to use it.

Your periods usually become much lighter and shorter and sometimes less painful. They may stop completely after the first year of use. This can be useful if you have heavy, painful periods.

Two types of IUS (Mirena and Levosert) can be used specifically to treat heavy periods.

It works for three to eight years depending on the type.

It can be used if you’re breastfeeding. 

Your fertility returns to normal as soon as the IUS is taken out.

It’s useful if you can’t use oestrogens, like those in the combined pill, the contraceptive patch and the contraceptive vaginal ring.

It’s not affected by other medicines.

Mirena can be used to protect the lining of your uterus (womb) if you’re having hormonal replacement therapy (HRT).

Your bleeding pattern may change in a way that’s not acceptable to you; this is particularly true when you first start the IUS (or any method of hormonal contraception). Some women may stop bleeding completely with the IUS and this is nothing to worry about.

The IUS doesn’t protect you against sexually transmitted infections, so you may want to use condoms as well.

It requires an internal examination and a procedure to insert and remove it.

You may get some temporary side effects when you first start using the IUS, such as skin changes, breast tenderness and headaches. These often settle within a few months.

Some people develop small fluid-filled cysts on their ovaries that may cause pain. These aren’t dangerous and usually don’t need treatment.

There’s a small chance of you getting an infection during the first few weeks after an IUS is put in. You may be advised to have a check for sexually transmitted infections before an IUS is fitted or at the time it’s fitted.

The IUS can be pushed out (expulsion) by your uterus (womb) or it can move (displacement). This isn’t common. It’s more likely to happen soon after the IUS has been put in and you may not know it’s happened. Your doctor or nurse will teach you how to check the threads every month so you know the IUS is in place.

It’s not common, but there’s a very small risk that the IUS might go through (perforate) your uterus or cervix when it’s put in. The risk is higher if you’ve recently given birth or are breastfeeding. This may cause pain, but often there are no symptoms and the uterus or cervix will heal by itself. The risk is low when an IUS is fitted by an experienced doctor or nurse. If it does happen, the IUS may have to be removed by surgery.

You’re unlikely to become pregnant while using an IUS but if you do, there’s a small risk of ectopic pregnancy. You’re less likely to have an ectopic pregnancy while you’re using an IUS than when you’re not using any contraception.

Research about the risk of breast cancer and hormonal contraception is complex and contradictory. Research suggests women who use hormonal contraception may have a small increase in the risk of being diagnosed with breast cancer compared to women who don’t use hormonal contraception.

You can normally have the IUS inserted at any point in your menstrual cycle.

There is special guidance if you have just had a baby, abortion or miscarriage.

You can have the IUS inserted at any time in your menstrual cycle if you’re sure you’re not pregnant.

If you have the IUS inserted:

  • On the first day of your period, you’ll be protected from pregnancy immediately.
  • Up to, and including, the seventh day of your period, you’ll be protected from pregnancy immediately.
  • At any other time in your menstrual cycle, you’ll need to avoid sex or use additional contraception, such as condoms, for the first seven days after your IUS has been inserted.

If you have a short menstrual cycle with your period coming every 23 days or less, starting the contraceptive IUS as late as day 7 of your period may not give you immediate contraceptive protection. This is because you may ovulate (release an egg) early in your menstrual cycle. You may wish to talk to your doctor or nurse about this and whether you need additional contraception for the first seven days.

The IUS isn't affected by any medication (including common antibiotics or liver enzyme inducing medication), diarrhoea or vomiting.

The IUS is inserted into your uterus (womb). A doctor or nurse will examine you internally to check the position and size of your uterus. Sometimes they’ll check for any existing infection. This can be done before or at the time of fitting the IUS.

Sometimes you’ll be given antibiotics at the same time the IUS is fitted.

Your appointment will last 30-45 minutes. Inserting the IUS usually takes around 5-10 minutes.

It can be uncomfortable or painful for some people, and you may be offered a local anaesthetic. Your doctor or nurse should talk to you about this.

You may get a period-type pain and some light bleeding after the IUS is fitted. Pain-relieving medicine can help with this.

If you feel unwell and have pain in your lower abdomen, with a high temperature or a smelly discharge from your vagina, see a doctor or go back to the clinic where the IUS was fitted as soon as possible. You may have an infection.

An IUS has two threads attached to the end that hang a little way down from your uterus (womb) into the top of your vagina. The doctor or nurse will teach you how to feel the threads to make sure the IUS is still in place. You should do this a few times in the first month and then at regular intervals, for example after your period.

It’s very unlikely that an IUS will come out but if you can’t feel the threads, or if you think you can feel the IUS itself, you may not be protected from pregnancy. If this happens see your doctor or nurse straight away and use an extra contraceptive method, such as condoms. If you had sex recently, you might need to use emergency contraception.

Rarely, a partner may say they can feel the threads during sex. If this happens, ask your doctor or nurse to check the threads.

If you want to stop using the IUS, go back to the doctor or nurse and ask for it to be taken out.

Your periods and fertility will return to normal when the IUS is removed.

If you don’t want to get pregnant, use additional contraception, such as condoms, or avoid sex, for seven days before the IUS is taken out and use another method of contraception from the day it’s removed.

If you want to try for a baby, start pre-pregnancy care such as taking folic acid and stopping smoking.

Ask your doctor or nurse for advice.

A trained doctor or nurse can take the IUS out by pulling gently on the threads. If you want to keep using an IUS, the doctor or nurse can put in a new one at the same time.

The IUS is very effective and it’s unlikely you’ll get pregnant.

If you do, there’s a small increased risk of ectopic pregnancy. An ectopic pregnancy develops outside the uterus, usually in a fallopian tube. If you think you might be pregnant and/or have a sudden or unusual pain in your lower abdomen, seek medical advice as soon as possible. You will need to have an ultrasound scan to rule out an ectopic pregnancy.

It is usually recommended to remove the IUS as soon as possible (this is irrespective of if you want to continue with the pregnancy or have a termination of pregnancy). The doctor or nurse will discuss this with you.

If you get pregnant and want to continue the pregnancy, talk to a doctor or nurse as soon as possible.

If you do not want to continue the pregnancy you can self refer to an abortion care service.