Hormonal coil (IUS)

The hormonal coil, also known as the IUS (intrauterine system) is a small T-shaped plastic device that sits in your womb and releases the progestogen hormone. It is long-acting and reversible, so you can take it out if you want to get pregnant.

It is 99% effective at preventing pregnancy.

How it works

How to use it

The IUS is fitted by a trained clinician. Once it is in place, you don't have to think about contraception. It won't interrupt sex and your partner should not be able to feel it.

It can be removed at any time by a trained doctor or nurse, but you must use condoms as well or abstain from sex for 7 days prior to removal.

There are four brands of IUS hormonal coil available in the UK - the Kyleena, Mirena and Levosert coils, which all last for five years, and the Jaydess coil, which lasts for three years. Brook services use the Kyleena and Mirena coil.

What it does

The IUS releases a progestogen hormone which prevents pregnancy by:

  • Thickening the mucus in the neck of the womb, so it is harder for sperm to penetrate the womb and reach an egg.
  • Thinning the lining of the womb, so there is less chance of a fertilised egg implanting into the womb.
  • In some people, the IUS also stops the ovaries from releasing an egg (ovulation), but most people will continue to ovulate.

Pros and Cons


  • The IUS prevents pregnancy for up to three or five years depending on the brand of IUS.
  • It doesn't interrupt sex.
  • Your periods may be lighter, shorter, or they may stop completely.
  • Your fertility will return to normal after the IUS has been removed.
  • 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.
  • It is not affected by vomiting, diarrhoea or other medicines like some methods of contraception.


  • It does not protect against STIs.
  • It may cause irregular bleeding at first.
  • It can cause temporary side effects such as skin problems, headaches, breast tenderness or minor changes to your mood or libido.
  • 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 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.

How is the IUS fitted?

Before you have the IUS fitted, you may be tested for any existing infections, such as STIs, so that any infections can be treated beforehand.

Having a coil fitted can be uncomfortable and painful but the pain shouldn't last long and is described as quite similar to period pains. A fitting is likely to be less painful if you have had natural birth (vaginal delivery) as your cervix will have previously been stretched.

  • Whilst you lie down, with your knees bent, a speculum will be used to hold your vagina open (the same instrument is used when having a smear test done). Local anaesthetic gel is applied to the cervix and this feels cold.
  • The clinician will then use forceps to hold the cervix steady in order to determine the size and position of your womb with a sterile probe.
  • The coil comes with its arms folded down packed inside a narrow tube. The clinician will insert the tube into the vagina, through the cervix and into your uterus (womb).
  • Then they will pull the plastic tube out, leaving the coil in place allowing the arms of the coil to fold open. Before the speculum is removed, the strings of the coil are cut, leaving 1 to 2 cm hanging down at the top of your vagina so that you can feel to make sure it is still in place.

The whole process should take about 5 minutes.

People normally have some cramping pain afterwards so it is recommended you take some pain killers just before your appointment.

Occasionally people feel nauseous or faint afterwards. They may need to lie down for 5-10 minutes but are usually fine after a short while. The clinician will always make sure you are recovered and happy to make your way home before letting you leave.

Some people prefer to have no plans after their appointment so that they can be relax at be comfortable at home afterwards.

It is fairly common for people to experience some slight cramping and / or spotting for a couple of days after a fitting. You will be asked to make an appointment after 6 weeks where the clinician will check your coil is in place and to see how you are getting on.

When can the IUS be fitted?

The coil can be fitted at any time during your monthly menstrual cycle, as long as you're definitely not pregnant.

If the IUS is 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.

We advise that you:

  • Continue with your current barrier method of contraception until one week after the fit or
  • Abstain from sex from the first day of your period until one week after the fit.

If you have a short menstrual cycle, where your period normally comes every 23 days or less, you will have to start the IUS in the first six days (because you might ovulate early in your menstrual cycle).


How quickly does the IUS work after it’s fitted?

If it is fitted in the first five 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 additional contraception for the first 7 days.

Can I use tampons or a mooncup with an IUS?

Yes, whilst using the IUS you can use tampons, pads or a mooncup.

Does the IUS cause weight gain?

There's no evidence that an IUS will affect your weight.

Will my partner feel the threads?

Your partner shouldn't be able to feel your IUS during sex. If they can feel the threads, get your GP or clinician to check your IUS is in place. They may be able to cut the threads a little.

Is there an increased risk of cancer from using the IUS?

There's no evidence that having an IUS fitted will increase the risk of cervical cancer, cancer of the uterus or ovarian cancer.

Who is the IUS suitable for?

The IUS may not be suitable for you if you have or have had certain health conditions.

  • Breast cancer (currently or in the last five years)
  • Cervical cancer
  • Liver disease
  • Heart disease
  • Problems with your womb or cervix or unexplained vaginal bleeding between periods or after sex
  • An untreated STI or pelvic infection

Can I use the IUS if I’m approaching menopause?

If you're 45 or older when you have the IUS fitted, it can be left until you reach menopause or you no longer need contraception. The IUS can also be used for Hormone Replacement Therapy (HRT).

Could the IUS get lost inside my body?

The GP or clinician that fits your IUS will teach you how to feel for the threads and check that the IUS is still in place. If you can't feel the threads or if you think the IUS has moved, you may not be fully protected against pregnancy.

See your doctor or nurse straight away and use extra contraception, such as condoms, until your IUS has been checked. It will always be able to be removed.

Could I get an infection from the procedure to fit the IUS?

There is a very small risk of infection (1 in 100). If you have any of the following symptoms within a few days of having an IUS fitted, you should see your GP (or clinician who fitted the IUS) straight away:

  • Pain in your lower abdomen
  • A high temperature
  • A smelly discharge from the vagina

Will the IUS affect my future fertility?

Fertility will return to normal when the IUS is removed.

If you decide to have your IUS taken out, but you don’t want to get pregnant, you will need to use condoms for 7 days before you have it removed. This is because sperm can live for up to 7 days inside the body.

What if I want to have the IUS removed?

A coil can be removed at any time by a trained doctor or nurse.

If you're not going to have another coil put in and you don't want to get pregnant, use another method (such as condoms) for seven days before, as sperm can live for up to seven days inside the body.

Removal of a coil is a very quick procedure (about 30 seconds). It may be a little uncomfortable but is less uncomfortable than the fitting procedure.

What happens if I become pregnant while I am using an IUS?

Although this is unlikely, if the IUS fails and you become pregnant, you should have it removed as soon as possible if you are continuing with the pregnancy. You should also have a scan to ensure the pregnancy is not ectopic.

Can my womb be damaged by the IUS?

In fewer than 1 in 1,000 cases, an IUS can make a tiny hole in the womb or neck of the womb (cervix) when put in. The risk of perforation is extremely low. Contact your GP straight away if you feel a lot of pain in the lower abdomen after having an IUS fitted. If there is a suspected perforation, go to A&E to see a specialist. If perforation occurs, you may need surgery to remove the IUS.

Is it possible for my body to reject the IUS?

The coil can be pushed out by your uterus or it can move, however this is not common. This is more likely to happen soon after it has been put in. This is why your doctor or nurse will teach you how to check your coil threads every month and also arrange to check it for you 6 weeks after your fitting.

What happens if I get an STI while I have an IUS?

If you get an STI while you have an IUS fitted, it could lead to pelvic infection. STIs and pelvic infections need to be treated as soon as possible. An IUS doesn't protect you against STIs, so you may also have to use condoms when having sex.

Can I use the IUS after having a baby/whilst breastfeeding?

Yes, you can fit the IUS 28 days or more post-delivery. An IUS can be used safely while you are breastfeeding and will not affect your milk supply.