Mirena is a type of intrauterine contraceptive that can help prevent pregnancy for up to five years. This device is inserted into the uterus and slowly releases a hormone that stops ovulation (in some women), alters the cervical mucus, and changes the lining of the uterus. Potential side effects of Mirena include a decreased sex drive, nausea, and headaches.

What Is Mirena?

Mirena® is an intrauterine contraceptive (IUC) used to provide long-term birth control. It is a small, flexible polyethylene (plastic) device that contains levonorgestrel, a progesterone hormone. Mirena is designed for women who have had at least one child. Mirena is also approved to treat heavy menstrual bleeding in women who choose intrauterine contraception.
(Click Mirena Uses for more information on what it is used for, including possible off-label uses.)

Who Makes Mirena?

It is made by Bayer HealthCare Pharmaceuticals Inc.

How Does It Work?

There are two types of intrauterine contraceptives (IUC), non-hormonal copper devices (known as intrauterine devices, or IUDs) and hormonal devices (known as intrauterine systems, or IUSs). Mirena is an IUS, meaning that it contains a hormone and relies on the hormone for preventing pregnancy. Your healthcare provider inserts the device into the uterus, where it can remain for up to five years.
Mirena slowly releases a low level of levonorgestrel (a progesterone hormone). In some women (less than half), it works by stopping ovulation (the maturation and release of eggs from the ovaries). However, for most women, Mirena works in other ways (and ovulation continues as usual). In these women, Mirena alters the cervical mucus (the fluid of the cervix, which is the lower, narrow part of the uterus that is connected to the vagina), making it more difficult for sperm to enter the uterus. It also decreases the ability of sperm to survive in the uterus. Lastly, it alters the lining of the uterus (called the endometrium), making it less receptive to an embryo.
Last reviewed by: Kristi Monson, PharmD
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