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IUS (intrauterine system)

About the IUS (known as a mirena coil / jaydess)

It is more than 99% effective in preventing pregnancy. The IUS is a long-acting reversible contraceptive (LARC) method. This means that once it's in place, you don't have to think about it each day or each time you have sex. 

It works for 3-6 years, depending on the type, so you don't have to think about contraception every day or each time you have sex. It can also be removed at any time by a specially trained doctor or nurse, and you'll quickly return to normal levels of fertility. If you don’t want to get pregnant you should avoid having unprotected sex for a week before the IUS is removed.

The IUS can make your periods lighter, shorter or stop altogether, so it may help women who have heavy periods or painful periods. 

The IUS does not protect against sexually transmitted infections (STIs). By using condoms as well as the IUS, you'll help to protect yourself against STIs.

Our clinics will only fit an IUS for contraceptive purposes. If you have been advised to have a IUS for the treatment of heavy periods only or as part of HRT, please contact your GP.

How it works

The IUS looks similar to the IUD (intrauterine device) but works in a slightly different way. Rather than releasing copper like the IUD, the IUS releases a progestogen hormone, which is similar to the natural hormone progesterone that's produced in a woman's ovaries.

Progestogen thickens the mucus from the cervix (opening of the womb), making it harder for sperm to move through it and reach an egg. It also causes the womb lining to become thinner and less likely to accept a fertilised egg. In some women, the IUS also stops the ovaries from releasing an egg (ovulation), but most women will continue to ovulate.

If you're aged 45 or older when you have the IUS fitted, it can be left until you reach menopause, or you no longer need contraception.

An IUS can be fitted at any time during your menstrual cycle, as long as you are not pregnant or have any risk of pregnancy (you have not had unprotected sex). Your nurse or doctor who fits the IUS will ask you questions about your last period and any sex you have had since then to check it is safe to fit. If it isn’t safe you may be advised to return another day and offered a short-term method of contraception to use until then.

Once fitted you should avoid sex or use condoms for the next 7 days.

Where you can get the IUS from

If you think the IUS is the right contraception choice or if you’ve had unprotected sex since your period and want to check it’s still ok to have your IUD fitted , you can:

Our partner GPs also fit the IUS for contraceptive purposes.

If you need to bring your child/children with you to your appointment we recommend you bring another adult with you to care for them.

More information

 Visit NHS Choices - IUS 



Last updated: 16/06/2023