Mirena Side Effects (Hormonal IUD): What are They and How Bad are They?

Mirena Side Effects (Hormonal IUD): What are They and How Bad are They?

Women of child-bearing age often want to prevent pregnancy until they are ready to have children, but not everyone wants to remember to take a pill each day, hassle with buying condoms, or regularly replace patches or rings. Intrauterine devices (IUDs) offer women additional control over their fertility and are 99 percent effective at the prevention of pregnancy, but some women aren’t sure about the safety of these devices. As IUDs have grown in popularity, it has become clear that while they can cause certain side effects, they’re also one of the most convenient and effective forms of birth control on the market. Hormonal IUDs like Mirena are effective at preventing pregnancy, but what side effects does Mirena cause and how bad are they?

What is Mirena?

Mirena is a brand name IUD that releases a hormone called levonorgestrel. Like other IUDs, Mirena is a small, flexible device that is shaped like a T and can be placed inside the uterus to prevent pregnancy. Mirena was first approved by the U.S. Food and Drug Administration (FDA) in 2000 and has been used regularly by women in the United States in the two decades since. IUDs like Mirena are placed by a trained healthcare provider during an office visit, and placement of the device does not require surgery. Mirena can prevent pregnancy for up to six years, but it also has a number of other purposes and uses.

Why do women use Mirena?

While most women think of Mirena as a form of long-lasting birth control and use the IUD to prevent pregnancy, Mirena is also the first and only IUD that has been approved by the FDA to treat heavy periods. Women who want to prevent pregnancy and also have heavy periods are able to achieve both benefits while using Mirena, which is not the case for other IUDs. Mirena is one of the most effective forms of birth control; like other IUDs, it is more than 99 percent effective at preventing pregnancy. However, Mirena cannot be used as an emergency contraceptive, so placing the device after having unprotected sex will not prevent pregnancy. The device also does not prevent infection with HIV or other sexually transmitted diseases.

How does Mirena work?

Mirena works by releasing small amounts of levonorgestrel, a type of progestin hormone, into the uterus; Mirena does not contain any form of estrogen and is a second generation progestin hormone IUD. Although progestin is released locally, its effects on the body are systemic through something called the hypothalamic-pituitary-adrenal (HPA) axis. This is a hormonal network that begins in the brain and flows to the thyroid, pancreas, ovaries and adrenal glands. Progestin acts on receptors of the brain that play a role in everything from mood to cognition, stress response, thyroid function, immune function and more. Dysregulation of this axis can contribute to imbalances in the immune system, mood, sleep, metabolism (weight gain), and cardiometabolic disorders. 

Exactly how Mirena works is unknown, it is believed that the device works in three ways to prevent pregnancy:

  • Inhibits sperm from reaching or fertilizing the egg
  • Thins the uterine lining
  • Thickens cervical mucus to prevent sperm from entering the uterus

The hormones contained in Mirena impact the hypothalamic-pituitary-adrenal (HPA) axis, which impacts the way the body responds to stressful life events. Dysregulation of this axis can contribute to disorders of the immune system, memory impairment, obesity, and cardiometabolic disorders. Despite the potential impact to the HPA axis, Mirena has been shown to be more than 99 percent effective at preventing pregnancy, and it also helps to treat heavy periods by thinning the lining of the uterus, thereby reducing the volume of menstrual flow. Some women do experience irregular periods in the first three to six months after Mirena placement and may have frequent spotting, light bleeding, or cramping as their bodies adjust to the device. Other women experience heavy bleeding that gradually diminishes over time, and some will have their periods stop entirely.

What side effects are associated with Mirena?

Hormonal IUDs like Mirena do have some side effects, including both common and serious side effects. Some women may find the side effects beneficial depending on how their body responds to the medication, while others do not. Common side effects associated with Mirena include:

  • Pain, bleeding, or dizziness after placement of the device via dilation of the cervix (should resolve within 30 minutes)
  • Changes in menstrual bleeding, including:
    • Heavier periods when first starting Mirena
    • Spotting or bleeding between periods
    • Missed periods
  • Increase in pain or cramps during your period, particularly in the first few months after the device has been placed
  • Headaches or migraine
  • Fatigue
  • Nausea
  • Enlarged ovaries
  • Expulsion of the device
  • Weight gain
  • Unwanted hair growth
  • Acne
  • Breast tenderness
  • Inflammation of the vagina, causing pain and/orvaginal discharge
  • Development of ovarian cysts
  • Hair loss
  • Decreased sexual desire

Other side effects of Mirena are more serious and require immediate medical attention. If you experience any of the following issues, seek medical attention right away:

  • Pelvic inflammatory disease
  • Allergic reaction
  • Heart attack
  • Life threatening infection that develops within a few hours of placement of Mirena
  • Liver problems
  • Stroke
  • Ectopic pregnancy and intrauterine pregnanc

Another serious potential side effect of Mirena is the embedment or perforation of the device in the uterus. When Mirena attaches itself to the wall of the uterus, embedment is said to occur; perforation is characterized by the device puncturing the wall of the uterus. In either situation, Mirena will need to be removed surgically. If you experience pain in the abdomen, vaginal bleeding, fever, or chills, speak to your doctor right away about the status of your Mirena device.

How bad are the side effects associated with Mirena?

Every woman’s experience with Mirena will be different, and while some women may experience few side effects, others may have a higher incidence of experiencing unpleasant symptoms. Hormonal forms of birth control like the Mirena IUD are believed to cause certain side effects when used long term because they deplete the body of essential nutrients, which can cause imbalances in the body and undesirable symptoms. The World Health Organization (WHO) notes that hormonal contraceptives can cause depletions of nutrients such as folate (vitamin B9), vitamins B2, B6, B12, C, and E, as well as magnesium, selenium, and zinc. 

Women who are looking to minimize the potential side effects associated with Mirena may find support from a dietary supplement that is specifically designed to support the nutritional deficiencies that can result from the long term use of hormonal contraception. Biochemistry is a balancing act, and women have unique nutritional needs while using birth control like Mirena. Therapeutic doses of the missing vitamins and minerals, as well as the addition of mitochondrial antioxidants, can help to decrease the incidence of side effects including low sex drive, weight gain, mood swings, headaches, and fatigue.

What are the benefits of using Mirena?

Mirena is a popular form of birth control because it has many benefits. The IUD is more than 99 percent effective at preventing pregnancy, and for women with heavy periods, it can reduce the amount of menstrual bleeding each month. Mirena eliminates the need to take a pill daily and can be used for five years before it needs to be replaced. Mirena can be removed at any time if a woman decides that she would like to try to conceive, and fertility returns very quickly. 

What risks are associated with using Mirena?

The long-term risks most commonly associated with Mirena include the development of ovarian cysts, an increased possibility of developing pelvic inflammatory disease (PID), expulsion of the device from the uterus, perforation of the uterus by the device, and ectopic pregnancy or intrauterine pregnancy. Of these, the most common risk is the development of ovarian cysts, which is estimated to occur in 12 percent of women who use the device. Most cysts disappear on their own within two to three months, but some may cause pain or require surgical removal.