Mirena IUD Usage Precautions

If you have already inserted a Mirena (LNG-IUS, levonorgestrel-releasing intrauterine system), many people are flustered by the bleeding changes during the first few months or wonder "is this normal." This article is not one that introduces what kind of device the Mirena is, but focuses on what someone already using it should take care of, from after insertion to removal. Let me look in order at the changes in bleeding patterns, the distinction between normal adaptation reactions and signals requiring a visit, thread self-checking and regular checks, and considerations for long-term use such as bone and breast. If you are curious about the principle of the device itself or insurance coverage, you may first look at the article organizing the principle and side effects of the intrauterine device.

That bleeding becomes irregular early in Mirena use is an expected change that arises as the device acts directly on the uterine lining. The Mirena releases the corpus luteum hormone levonorgestrel locally within the uterus to suppress the proliferation of the lining, and in this process the lining thins and the bleeding pattern changes. According to the summaries of the UK Faculty of Sexual and Reproductive Healthcare (FSRH, 2023) and the American College of Obstetricians and Gynecologists (ACOG, 2017), a wide range of patterns can appear—small spotting, frequent bleeding, prolonged bleeding, or even amenorrhea in which periods almost disappear.

In the clinic, this irregular bleeding usually stands out most in the first 3–6 months after insertion and shows a flow of stabilizing over time. Many people settle, in the long term, in the direction of decreased bleeding amount or lighter periods. Even if amenorrhea comes, this is the result of the hormone keeping the lining thin, not something accumulating in the body, so there is no need to view it as a problem in itself.

Bleeding does not all carry the same meaning, and the key is to divide it by duration and accompanying symptoms. Light spotting in the first few months is a common adaptation reaction, but bleeding that newly starts or whose pattern abruptly changes even after sufficient time has passed must be examined separately. The table below is a general division standard frequently guided in the clinic.

ACOG (2017) advises bearing in mind the possibility of ectopic pregnancy when bleeding suddenly arises in someone who had been amenorrheic, or when menstruation is late and accompanied by lower-abdominal pain. As in the last row of the table, if fever, foul-smelling discharge, and severe pelvic pain come together, it is safer to confirm with a visit rather than passing it off as an adaptation reaction. If abnormal vaginal bleeding recurs, you can check the cause together at the care that handles abnormal vaginal bleeding.

If bleeding changes become a daily burden and it is hard to judge alone, feel free to ask. Get a consultation on bleeding patterns

The most practical habit for safely maintaining a Mirena is thread (thread) self-checking. FSRH (2023) recommends confirming the position of the thread once 4–6 weeks after insertion, and thereafter checking at a regular time such as once a month or right after a period. Except for cases inserted right after delivery, it is also guided that a set regular visit is not necessarily required when there is no particular abnormality. That is, self-checking is the core, and the regular check is closer to a safety net used when there are symptoms or when the check result differs from usual.

If on self-check the thread is not felt, or has become shorter or longer than usual, we suspect the possibility that the device has partly come out (partial expulsion) or its position has changed. ACOG (2017) explains that partial or complete expulsion can occur without you knowing and the contraceptive effect can disappear. In this case, it is safe to use backup contraception until pregnancy is ruled out and to confirm the position with a visit.

• Thread not felt or its length changed: possibility of expulsion/position shift, confirm with a visit
• A hard plastic tip is felt: the device may have descended, a check is needed
• The check itself is hard or anxiety-inducing: request a position check at the regular check

Infection risk is concentrated in time right after insertion. ACOG (2017) summarizes that the risk of pelvic inflammatory disease is mainly concentrated in the first 3 weeks after insertion and thereafter returns to the general population level, and that the absolute risk itself is on the low side. So if fever, pelvic pain, or foul-smelling discharge arise within the first few weeks after insertion, you must examine more carefully given the timing.

The worry that the Mirena greatly lowers systemic hormones and weakens bone can be largely relieved by looking at how it works. The Mirena is a device that releases hormone locally within the uterus, sending out about 20µg per day early on and decreasing to about 10µg around 5 years. It is a known fact that when the female hormone estrogen lowers, bone resorption increases and can affect bone density, but the key is how much the Mirena lowers systemic estrogen.

In clinical experience, even when using a Mirena, the ovaries' ovulatory function is generally maintained, and there are many people whose systemic estrogen does not drop greatly. In fact, there is a report that the average estrogen level of the Mirena-using group is measured similar to the follicular-phase level of menstruating women, and a study that found no difference in bone density from women using a non-hormonal intrauterine device. This is different in nature from the bone density decline seen in subcutaneous implant contraception with a stronger systemic effect, or amenorrhea due to an eating disorder.

On the other hand, there is also a study in which bone density at some sites was measured low with long-term use, so the conclusion is closer to "hard to assert in one direction." Therefore, a healthy woman with no risk factors who usually exercises steadily need not unconditionally avoid the Mirena for reasons of bone density, and in cases with fracture risk factors or the possibility of premature menopause, it is reasonable to decide in consultation with the attending physician. If you are curious about hormonal change overall, you can get a consultation at hormone intensive care.

As for the association with breast cancer, "results differ depending on the studies included" is a more accurate expression than "definitively bad." The body level of levonorgestrel released by the Mirena is on the lower side than when taking an oral contraceptive of the same ingredient, and in the past it was also used for the purpose of protecting the lining. In meta-analyses too, depending on which studies are included, it is divided into the side where the association increases and the side where it does not.

There is an interpretive limit here: it has been pointed out that selection bias can be involved, since among women who chose intrauterine contraception are mixed those who chose this method because of higher weight or a contraindication to oral contraceptives. The point that the effect on the breast differs depending on the type of corpus luteum hormone must also be considered together.

To summarize, there is not sufficient basis to uniformly avoid intrauterine contraception such as the Mirena merely on the grounds of worrying about breast cancer. However, if you have individual risk factors such as a history of breast cancer or family history, I recommend deciding by consulting the indication with an obstetric-gynecologic specialist. If you are pondering which contraceptive method suits you, the article organizing contraceptive methods or the pregnancy and contraception clinic consultation helps.

The removal and replacement of a Mirena are not difficult if you know the set timing and prepare in advance. Generally, the Mirena maintains its contraceptive effect for the approved period, and as that point approaches, you consult about whether to replace it with a new device after removal or switch to another contraceptive method. Removal itself is a relatively simple process of gently pulling out the thread, but if the thread is not visible or has gone inside the cervix, additional confirmation may be needed.

There are situations where removal or a check should be considered even before the scheduled time. ACOG (2017) advises that removal is needed when the thread is not visible, or when the device is confirmed to have been expelled or to have perforated the uterine wall. Uterine perforation is a rarely reported complication, and the risk can be somewhat higher when breastfeeding, postpartum, or when the uterus is severely retroverted, so it is watched carefully from the time of insertion.

If you think of the Mirena not as "done once it's in" but as "a device managed together until the time of removal/replacement," you are less shaken by bleeding changes and do not miss the timing of regular checks. If you are confused about the timing of checks during use, or want to consult about removal/replacement, please feel free to contact us. Get a consultation on Mirena checks

The small changes that arise during use are mostly the adaptation process, but just knowing which signals can be passed over and which must be confirmed greatly reduces anxiety. Making regular self-checking a habit and confirming with a visit when there are changes different from usual is the most reliable way to use a Mirena safely for a long time.

Written by: Lee Dong-hee Director · Obstetrics and Gynecology Specialist · See physician profile

First published December 5, 2023 · Last reviewed May 30, 2026

References: FSRH Guideline Intrauterine Contraception (2023), ACOG Practice Bulletin Long-Acting Reversible Contraception (2017)

This article is intended to provide general health information and does not replace individual diagnosis or treatment. If you have symptoms, please consult through a medical visit.