What Is a Levonorgestrel-Releasing Intrauterine Device
A levonorgestrel-releasing intrauterine device is a small, T-shaped plastic frame placed inside the uterus that releases a steady, low dose of the hormone levonorgestrel. The hormone thickens cervical mucus to block sperm, thins the uterine lining, and in many users suppresses ovulation. Because it releases hormone locally rather than circulating through the body at high levels, it is classified as a long-acting reversible contraceptive, or LARC, and is among the most effective reversible birth control methods available.
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In the United States, two main brands of levonorgestrel IUD are in widespread use: Mirena, which is approved for up to eight years of contraception and also treats heavy menstrual bleeding, and Liletta, approved for up to eight years as well. Skyla and Kyleena are smaller devices with lower hormone doses approved for three to five years. The specific duration of use depends on the brand and the condition being treated, and a clinician should confirm the approved window for each product.
How the Levonorgestrel IUD Works
The device releases levonorgestrel continuously at a controlled rate through a membrane on the vertical stem. The hormone acts primarily on the cervical mucus, making it thick and hostile to sperm, and on the endometrium, thinning it so that implantation is less likely. In many users, ovulation is also suppressed, though this effect varies across brands and over time. Because the hormone stays mostly within the uterus, systemic side effects tend to be fewer than those seen with estrogen-containing methods.
Insertion is typically done in a clinic or office setting. The provider measures the uterine cavity, cleans the cervix, and uses a speculum to pass the device through the cervical canal into the uterus. The whole process takes a few minutes, and some providers recommend taking a pain reliever beforehand or using a local anesthetic, especially for people who have not given birth vaginally.
Effectiveness and Real-World Use
Both hormonal and copper IUDs are among the most effective reversible contraceptives, with typical-use failure rates below one percent. The levonorgestrel-releasing intrauterine device does not depend on user adherence after insertion, which is the main reason its real-world effectiveness matches its clinical effectiveness. If a user wants to become pregnant, the device can be removed at any time, and fertility usually returns quickly.
No method is completely fail-proof. The IUD can expel, partially or completely, especially in the first few months after insertion or in people who have never been pregnant. Users are taught to check the strings regularly and to contact their provider if the strings feel shorter or if they feel the hard plastic of the device at the cervix.
Benefits Beyond Birth Control
The levonorgestrel IUD is used for more than pregnancy prevention. Mirena and Liletta are FDA-approved to treat heavy menstrual bleeding in women who also want contraception. The device can reduce menstrual blood loss by 80 to 97 percent over time, and many users develop lighter periods or stop having periods altogether after the first year. This makes it a common choice for people with anemia or heavy periods that interfere with daily life.
Because it is hormone-based, the levonorgestrel IUD does not contain estrogen, which makes it an option for people who cannot use estrogen-containing methods due to history of blood clots, migraine with aura, or other contraindications. It is also safe to use while breastfeeding, and it does not affect milk supply.
Side Effects and Risks to Consider
Common side effects in the first three to six months include irregular spotting or bleeding, and some users experience heavier bleeding and cramping in the weeks after insertion. Over time, periods usually become lighter. Hormonal side effects such as acne, breast tenderness, headaches, and mood changes can occur, though they are less common than with systemic hormonal methods.
Serious risks are rare but include uterine perforation during insertion, expulsion, and pelvic infection, most often in the first few weeks after placement. The IUD does not protect against sexually transmitted infections, so barrier methods are still recommended for people at risk.
Who Is a Good Candidate
The levonorgestrel-releasing intrauterine device is suitable for most healthy people who want long-term, reversible contraception. It is often recommended for people who want a method that is set and forget, for those who cannot tolerate estrogen, and for those dealing with heavy or painful periods. It is not recommended for people with current pelvic inflammatory disease, certain uterine abnormalities, or unexplained vaginal bleeding until evaluated. A thorough conversation with a clinician about medical history, future pregnancy plans, and the trade-offs of different IUDs helps ensure the right fit.