Women's Health Resources


What is Mirena?

Mirena is a tiny T-shaped piece of plastic that is placed into the uterus by your healthcare professional. Once Mirena is in place, it begins to slowly release small amounts of the hormone levonorgestrel into your uterus. It does not contain estrogen, so you can be free of estrogen-related side effects.

While there is no single explanation for how Mirena works, it may:

  • Block sperm from reaching or fertilizing your egg
  • Make the lining of your uterus thin (this may also result in benefits like less menstrual bleeding over time)
  • Stop the release of your egg from your ovary (but this is not the way it works in most cases)

It is believed that all 3 of these actions may work together to prevent pregnancy.

It is thought that the small amounts of levonorgestrel that are released by Mirena make your cervical mucus thick and tacky. This is why sperms are immobilized and can’t enter the uterus. And the thinning of the uterus is why you may have less menstrual bleeding over time. In fact, about 20% of women will have no period after one year, a safe (and, for most women, preferred) condition.

Other benefits of Mirena

99.8% effective in preventing pregnancy for up to 5 years (or less, if you choose)

  • Provides lower and steadier hormones than the Pill
  • Won’t cause significant weight gain
  • Easily removed with quick return to fertility
  • May also help shorten, lighten or even eliminate periods

Important Information About Mirena

Only you and your healthcare professional can decide if Mirena is right for you. Mirena does not protect against HIV or sexually transmitted diseases (STDs). Candidates for Mirena have had a child. Mirena is not appropriate for women who are or may be pregnant; or who may have a distorted uterine cavity; acute genital infections including pelvic inflammatory disease; cancer of the cervix, uterus, or breasts; unexplained vaginal bleeding; or acute liver disease or tumors (benign or malignant). In rare cases, perforation or embedment may occur. Mirena may become completely or partially dislodged. In the rare event you think you’re pregnant, contact your healthcare professional without delay to be evaluated for ectopic pregnancy. Ovarian cysts may occur and typically disappear. Persistent cysts should be evaluated. Missing periods or irregular bleeding is common in the first few months, followed by shorter, lighter periods.

Is Mirena Right for Me?

Mirena intrauterine contraceptive is appropriate for women who:

  • Have at least one child
  • Are looking for a hassle-free and reversible form of birth control for up to 5 years (or less, if you choose)
  • Are in a stable, mutually monogamous sexual relationship

It’s important for you and your healthcare professional to discuss which birth control method is right for you. Mirena offers effective birth control for busy women who want to keep life simple with a hassle-free contraceptive option.

Questions Your Healthcare Professional Will Ask to Help You Make the Right Choice About Birth Control.

  • Are you in a stable relationship in which you and your partner are not having sex with other people?
  • Have you ever had a pelvic infection (pelvic inflammatory disease or PID)?
  • Have you recently had a baby or are you breastfeeding?
  • Are you diabetic?
  • Were you born with heart disease or do you have heart valve problems?
  • Do you have problems with blood clotting or take medication to reduce blood clotting?

Side Effects Almost Always Decrease Over Time

Side effects with Mirena are most common during the first three months after insertion and decrease over time.

Percentage of Women Reporting Side EffectsDuring the First Three Months and Fifth Year of Use