What is Mirena?
Mirena is a type of treatment called an intrauterine system (IUS). It sits in the womb (uterus) and contains a hormone called levonorgestrel. Mirena may have been prescribed to you by your doctor for one or more of the following:
- As an effective long-term and reversible method of contraception. Mirena should be removed no later than 8 years after insertion when used as a contraceptive.
- For reducing heavy bleeding during your period. If used for this, Mirena should be removed no later than 8 years after insertion. Inform your healthcare professional if your symptoms return.
- If you are going through menopause, Mirena can be used in combination with an oestrogen as part of a hormone replacement therapy (HRT) regimen to protect the lining of your womb. Mirena should be removed no later than 4 years after insertion when used in HRT.
What is the Mirena intrauterine system (IUS) and what does it do?
An IUS is also known as a hormonal coil, or hormonal intrauterine device (IUD). It is a small plastic T-shaped device that sits in the womb and releases a hormone called levonorgestrel. Mirena releases a slow, continuous low dose of levonorgestrel into the womb. This means that only small amounts of the hormone enter the bloodstream.
Levonorgestrel mimics the hormone progesterone in the body. Levonorgestrel in Mirena can serve many functions in the body, such as:
- Thickening cervical mucus to make it harder for sperm to reach the egg
- Thinning the lining of your womb to prevent a fertilised egg from attaching, preventing pregnancy
- Thinning the lining of your womb to control heavy bleeding during periods
The T-shaped frame of the Mirena coil also causes some effects on the lining of the womb to prevent pregnancy.
As a contraceptive
Mirena can be used as a long-term and reversible method of contraception for up to 8 years. It is over 99% effective in preventing pregnancy, and is backed by more than 30 years of clinical experience in the UK.
To control heavy menstrual bleeding (HMB)
You may have been prescribed Mirena by your doctor if you suffer from heavy bleeding during your period. It works by reducing the amount of blood lost during your period. Mirena can be inserted for 8 years before it needs replacing to control HMB. Inform your healthcare provider if your symptoms return. You can get your Mirena removed at any time.
As a part of hormone replacement therapy (HRT)
If you are going through menopause, your doctor may have prescribed Mirena as a part of your hormone replacement therapy (HRT) to protect the lining of your womb. Mirena can be used for up to 4 years for this purpose.
The research behind Mirena
Mirena was the first levonorgestrel‐releasing intrauterine system available for use, initially approved in Finland in 1990. This was followed by approval in the UK in 1995, and it is now available in over 120 countries. It is 99.8% effective in preventing pregnancy in year 1, and maintains over 99% effectiveness over 5 years. In 2022, it was found to be effective for extended use as a contraceptive for up to 8 years.
Mirena is effective for heavy menstrual bleeding for up to 8 years unless symptoms return earlier, and for 4 years as part of an HRT plan.
Getting ready for Mirena and beyond
Mirena is a small device that is fitted inside the womb via the vagina and the cervix by a trained healthcare professional.
Before fitting Mirena, your healthcare provider may carry out some tests to make sure it is suitable for you. These may include a physical exam, a pregnancy test, and tests for sexually transmitted infections (STIs).
Once Mirena is fitted, your doctor or nurse will teach you how to check if it is in place. This is done by feeling for the two threads attached to the bottom of the Mirena coil. If you need more help on how to do this, contact your doctor or nurse. You should also read your Patient Information Leaflet.
It is important that Mirena is in the correct location in your womb, or it will not work properly. If you cannot feel these threads, it might be a sign that Mirena has moved out of place. Your doctor may confirm if Mirena has moved by performing an X-ray or ultrasound.
Depending on what it was prescribed for, Mirena needs to be replaced over time. You can get your old Mirena removed, and a new one inserted in the same appointment. Unless you plan on getting a new Mirena fitted immediately, you should use another mode of contraception such as condoms for at least 7 days leading up to the removal.
If you do not plan on getting another Mirena placed after removing an old one, you’ll need to use another mode of contraception if you do not wish to get pregnant.
What does the Mirena coil look like?
When you get Mirena, you may have to collect it from the pharmacy. It comes in a box that may look big for such a small contraceptive. This is because the box contains everything that is needed to fit Mirena, not just the coil itself. This includes the inserter tool that helps your doctor easily fit the IUS.
Even though Mirena is often called a ‘coil’, it is actually not coil-shaped. Mirena is a small, plastic T-shaped device with a white cylinder around the long end. There are two threads attached that lie in the vagina and allow you or your doctor to check if the coil is still present and in place. Mirena is 3.2 cm tall and wide, excluding the length of the strings.
Can anyone use Mirena?
Mirena may not be the right treatment for everyone. Please do not use Mirena and let your doctor know if you have any of the below medical conditions:
- You are pregnant or suspect that you may be pregnant
- Have or have had any type of cancer or suspected cancer including blood cancer (leukaemia) unless in remission; uterine, cervical and breast cancer
- Currently have or have had recurrent pelvic inflammatory disease
- Have or have had inflammation of the neck of the womb (cervix)
- Have an unusual or unpleasant vaginal discharge, or vaginal itching as this may indicate an infection
- Have or have had inflammation of the lining of your womb following the delivery of your baby
- Have or have had an infection of the womb after delivery, or after abortion during the past 3 months
- Have any condition which makes you susceptible to infections (a doctor will have told you if you have this)
- Have or have had an abnormal smear test (changes in the cervix)
- Have undiagnosed vaginal bleeding
- Have an abnormal womb or abnormal growths in the womb (fibroids) which distort the uterine cavity
- Have or have had liver problems
- Have or have had trophoblastic disease (a doctor will have told you if you have this)
- Are sensitive to the hormone levonorgestrel or to any of the ingredients in Mirena (see section 5, ‘What Mirena contains’ of the Mirena Patient Information Leaflet)
Mirena: frequently asked questions (FAQs)
Glossary
Coil: A common name for an IUS or an IUD. It is a small device placed inside the womb to prevent pregnancy.
Intrauterine device (IUD): A small T-shaped device, usually made with copper, placed inside the womb to prevent pregnancy without using hormones.
Intrauterine system (IUS): A small T-shaped device placed inside the womb that slowly releases a hormone.
Hormone replacement therapy (HRT): Treatment that replaces the hormones that the body makes less of during menopause, including oestrogen to relieve menopause symptoms and progesterone to protect the lining of the womb.
Levonorgestrel: One of the hormones that performs the function of a progestogen.
Menopause: Menopause is a condition caused by a fall in hormone levels in women between the ages of 45 or 55, but it can happen earlier.
Oestrogen: A hormone that is naturally made by the body. Oestrogen, along with progesterone is essential to puberty, the menstrual cycle, pregnancy, and menopause.
Progestogen: They are synthetic hormone drugs that mimic the body’s own progesterone.
Progesterone: A natural hormone made by the body. It helps control the menstrual cycle and supports pregnancy.
Abbreviations
IUD, intrauterine device; IUS, intrauterine system; HRT, hormone replacement therapy.
PP-MIR-GB-0315 | October 2026