The Mirena intrauterine device (IUD) is a long-acting contraceptive that works by releasing synthetic hormones into the uterus. Side effects of Mirena IUDs include changes in vaginal bleeding.

Many people use the Mirena IUD and have no unwanted effects. The response can vary from person to person.

In this article, we look at common and rare Mirena IUD side effects and how long they tend to last. We also investigate how Mirena compares with other forms of birth control.

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Below are some of the more common and less common side effects of the Mirena device.

Common side effects

Large studies suggest that these are the most common side effects of the Mirena IUD in people who have used it for 5 years:

Side effectPrevalence
Unscheduled bleeding from the uterus31.9%
Decreased bleeding from the uterus23.4%
Abdominal or pelvic pain22.6%
No periods18.4%
Headaches or migraine16.3%
Increased discharge14.9%
Heavier periods11.9%
Inflammation or infection of the vulva and vagina (vulvovaginitis)10.5%

Right after a doctor places the Mirena IUD, there might be unwanted effects, including pain, dizziness, and bleeding. These should go away within several days.

If these issues last longer, speak with a doctor, as it may mean that the IUD is not in the correct place.

Less common side effects

These side effects occurred in 5–10% of participants in studies of the Mirena IUD:

Side effectPrevalence
Breast pain8.5%
Back pain7.9%
Benign ovarian cysts7.5%
Period pain6.4%
Low mood or depression6.4%

Uncommon side effects

These unwanted effects occurred in fewer than 5% of study participants over a 5-year period:

PID may be a more common complication in people with other risk factors for the disease. For example, it may be more likely to develop in someone with a sexually transmitted infection (STI).

Some people report weight gain while using the Mirena IUD. However, most studies have not found a conclusive link between hormonal IUDs, such as Mirena, and weight gain.

A 2020 study comparing hormonal IUDs to another form of progesterone-only contraception, the injection, reported that participants using the injection gained weight while those with the IUD did not.

Another 2020 study found different results. In a diverse cohort of women, the researchers investigated the effects of the hormonal IUD, the copper IUD, and the birth control implant on weight gain.

After 36 months, hormonal IUD users gained 0.72 kilograms (kg) on average. After 60 months, this figure rose to 1.52 kg — twice the amount that participants using the copper IUD had gained.

This may indicate that the synthetic hormone in the Mirena IUD leads to a slight gain in weight. However, many factors can influence weight gain, including age. The study’s finding does not necessarily prove that the IUD causes a person to gain weight.

Some people experience mood changes while using hormonal contraception. Data suggest that around 6.4% of people who use the Mirena IUD experience low mood or depression within 5 years.

However, it is also worth noting that some people use hormonal contraception to manage mood changes caused by conditions such as premenstrual syndrome (PMS) and premenstrual dysphoric disorder (PMDD).

For people who experience significant mood changes due to hormonal fluctuations, a long-acting contraceptive such as the Mirena IUD may have a stabilizing effect.

In very rare cases, people using the Mirena IUD experience:

  • a severe allergic reaction
  • device expulsion
  • malpositioning
  • perforation of the uterus
  • severe pelvic pain
  • sepsis

All of these are serious issues that require immediate medical attention. For example, if the IUD perforates, or pierces, the uterus, the person usually needs surgery to retrieve the device.

If the IUD does perforate the uterus, it no longer works to prevent pregnancy, so the person may need a different method of birth control.

Mirena is more than 99% effective at preventing pregnancy, but if someone does become pregnant while using it, they have a higher risk of complications such as:

Anyone using this IUD who suspects that they are pregnant should speak with a doctor immediately.

In many cases, unwanted effects of the Mirena IUD are not long-term. According to Planned Parenthood, common side effects such as spotting between periods and cramping typically get better in 3–6 months.

Meanwhile, a person might want to have some side effects of Mirena, such as lighter periods or none at all. Research suggests that these are usually long-term changes for people who experience them while using the IUD.

Serious complications, such as PID, typically develop shortly after the person starts using the IUD — often within the first month. These issues are uncommon.

Speak with a doctor about any severe or persistent symptoms that occur during Mirena IUD use.

The Mirena IUD releases the hormone levonorgestrel, a synthetic form of progesterone. Levonorgestrel works by thickening the cervical mucus and thinning the lining of the uterus, which prevents pregnancy from taking place.

This synthetic hormone can also prevent ovulation, though it does not always have this effect.

The Mirena IUD has several key advantages. It:

  • Is highly effective: Mirena is more than 99% effective at preventing pregnancy. In one trial of 1,169 people aged 18–35, the 5-year pregnancy rate was 0.7%. In 12 months, only 0.2% of the participants became pregnant.
  • Can work immediately: If a doctor inserts the device within 7 days of the start of a period, it begins working immediately. If a person gets their IUD outside of this time frame, it can take 7 days to start working.
  • Long-acting and reversible: The Mirena IUD works for longer than almost any other contraceptive. A person does not have to remember to take pills or change patches.
  • Can have other benefits: A person may appreciate some side effects of the Mirena IUD. For example, people with heavy periods, PMS, or PMDD may find that it helps manage their symptoms.

However, there are some disadvantages, such as the:

  • insertion procedure, which can be painful
  • possibility of unwanted effects
  • small risk of infection and other complications
  • symptoms that may occur after the IUD is removed

It can take some time after a doctor removes the Mirena IUD for periods to return to normal. Also, some people experience a “Mirena crash,” which involves changes to their mood, sleep, weight, and skin health.

However, scientists have not studied this phenomenon. Its prevalence and the precise link with Mirena removal are still unclear.

Meanwhile, it is worth noting that IUDs do not protect a person from STIs. Using a barrier method, such as condoms, during sexual activity is still important.

The Mirena IUD works in a similar way to other progesterone-only types of birth control, including:

As a result, all of these contraceptives can cause similar side effects.

The Mirena IUD can last for 5 years, so it may be a more convenient option than taking a daily mini-pill or getting periodic injections.

Nonhormonal methods

Several types of birth control do not involve hormones. These include:

These may be better for people who have experienced side effects of hormonal contraceptives. However, these options have varying levels of effectiveness, and a person may find using a diaphragm, for example, less convenient.

The copper IUD is the only form of long-acting, reversible contraception that does not involve hormones. Condoms are the only method that can protect against STIs.

Before getting an IUD, ask the healthcare professional:

  • What side effects could I have, and when would they develop?
  • How can doctors manage the side effects?
  • Is there anything I can do to reduce them?
  • Could any of the side effects be an advantage?
  • What happens if I have severe side effects? Can I get the IUD removed immediately?
  • What are the symptoms of IUD complications?
  • Do I have a higher risk of complications due to my medical history?
  • What happens if I get pregnant?
  • What happens during the insertion procedure? What will you do to reduce the pain?

The most common Mirena IUD side effects include changes to uterine bleeding, abdominal pain, and headaches. Low mood and depression are uncommon but possible.

Anyone who has the Mirena IUD and experiences unwanted effects should contact a doctor for advice.

When deciding on a contraceptive, it can help to weigh up the options with a knowledgeable healthcare professional.