Mirena is a T-shaped intrauterine device (IUD). Bayer manufactures Mirena. The IUD contains levonorgestrel, a type of hormone that prevents pregnancy.

Mirena can remain in the body for up to five years because it releases the hormone over time. Patients should replace the IUD after five years.

The U.S. Food and Drug Administration (FDA) approved Mirena for the U.S. market in December 2000. The device’s label warns that Mirena may cause several serious complications.

Potential complications of Mirena include ectopic pregnancies and perforation of the uterine wall or cervix. Mirena may also cause severe infections, including pelvic inflammatory disease (PID) and sepsis.

As of February 2018, the FDA had not released any new side effect warnings for Mirena.

Women who say Mirena injured them filed thousands of lawsuits. As of Feb. 15, 2018, about 430 remained in federal court.

Mirena prevents pregnancy in women who want long-term birth control. It prevents pregnancy for up to five years.

Women can use Mirena if they have already had children or have never had children.

In 2009, the FDA approved Mirena to treat heavy periods(menorrhagia).

Studies show Mirena decreases menstrual blood loss by 62 to 94 percent after three months. The device reduces menstrual blood loss by 71 to 95 percent after six months of use.

Mirena and other IUDs do not protect against HIV or sexually transmitted diseases (STDs).

Bayer markets two other IUDs that are part of the Mirena family: Kyleena and Skyla.

Of the three IUDs, Mirena releases the largest amount of hormones. It also has a greater chance of stopping periods in the first year.

Kyleena and Skyla are smaller devices than Mirena. Skyla is only effective for three years.

Mirena works by releasing levonorgestrel. This hormone thins the lining of the uterus. It also thickens the mucus in the cervix.

As a result, sperm has a hard time moving and surviving in the uterus. This prevents pregnancy.

The thinning of the uterine lining can also reduce or stop menstrual bleeding.

Women get Mirena inserted during a regular doctor’s visit. The procedure takes about five minutes.

Doctors use a few tools to help insert the device but do not perform surgery.

Women should wait at least seven days after the start of their period to insert Mirena. Women who have just given birth, had a miscarriage or an abortion should wait at least six weeks.

A doctor or other trained health provider can remove Mirena at any time.

Eight out of 10 women who have had Mirena removed can get pregnant within a year, according to Bayer.

Health care providers must remove Mirena if it moves out of place. If a patient is not pregnant, she can get a new IUD inserted.

Some women may have pain during insertion and for several days after. Others experience only minor discomfort or cramping.

Severe pain, persistent pain or painful sex may be signs of serious side effects or complications associated with Mirena.

Infections can be serious. Signs of an infection include pain, bad-smelling discharge, unexplained bleeding or fever.

Patients with severe pelvic infections may need to have Mirena removed.

Other common side effects of Mirena include headache, breast tenderness, acne, nausea, bloating, cramps or painful periods, nervousness, hair loss, decreased sex drive, and unwanted hair growth.

Mirena caused weight gain in up to five percent of women in studies.

Women who are pregnant or suspect they may be pregnant, should not use Mirena.

Patients should discuss all medications with their doctor before using Mirena.

Drugs and herbal supplements can make Mirena less effective. Examples of these substances include some blood thinners, anti-anxiety drugs and anti-seizure medications. Anti-retroviral drugs, antibiotics and St. John’s Wort may also interact with Mirena.

Since the FDA approved Mirena, it has been the subject of more than 2,000 published studies.

Some findings were positive. Others were negative.

A study released in November 2017 found women who use IUDs may have a lower risk of cervical cancer.

But, a 2015 study showed that women who used Mirena reported higher than expected numbers of intracranial hypertension. Intracranial hypertension is a condition where the pressure increases in the skull. Symptoms may mimic a brain tumor.

Most recently, in 2018, the University of California published information on Mirena. It said Mirena may work longer than five years.

In a study of 500 women who kept their Mirena implant for seven years, only two women got pregnant.