Mirena is approved for up to eight years of use, and most side effects that develop are manageable or even beneficial. But the device does release a synthetic hormone into your body continuously, and over months and years that can produce real changes to your menstrual cycle, skin, mood, and ovarian function. Here’s what the evidence shows about each one.
How Mirena Works Over Time
Mirena contains 52 mg of levonorgestrel, a synthetic form of progesterone. It starts by releasing about 20 micrograms per day directly into the uterus, then tapers gradually over the years. Because the hormone acts locally, blood levels stay much lower than with oral contraceptives, but some levonorgestrel does enter your bloodstream. That systemic exposure is what drives most of the side effects beyond changes to your period.
The FDA approves Mirena for contraception for up to eight years, and for treating heavy menstrual bleeding for up to five years (after which it can be replaced if you still need it for that purpose).
Menstrual Changes and Lost Periods
The most common long-term change is a dramatic reduction in menstrual bleeding. By the end of the first year, about 57% of users have infrequent bleeding and 16% stop getting periods altogether. These numbers shift over time: by year eight, roughly 34% of users have no periods at all, while 26% bleed infrequently.
For many people this is a welcome effect, especially those who started Mirena for heavy periods. But it can also be unsettling if you’re not expecting it. Lighter bleeding or amenorrhea from Mirena doesn’t indicate anything harmful. Your uterine lining simply stays thin because of the local hormone exposure. Fertility returns quickly after removal, typically within a cycle or two.
Mood Changes and Depression Risk
This is one of the most debated side effects, and a large nationwide study published in The Lancet Regional Health offers some of the clearest data. Among users of the 52 mg levonorgestrel IUS (Mirena’s dose), the rate of first-time depression was about 31 per 1,000 person-years. For comparison, lower-dose hormonal IUDs had rates closer to 18 to 20 per 1,000 person-years. That translates to roughly 11 to 13 additional cases of depression per 1,000 users per year attributable to the higher dose.
Those numbers mean the absolute risk for any individual is still small, but the difference between doses is real and statistically significant. If you have a history of depression or notice persistent low mood, irritability, or anxiety after insertion, it’s worth taking seriously rather than dismissing as coincidence. The study authors also noted that some anxiety cases treated with antidepressants may have been captured in their data, so the mood effects may extend beyond depression alone.
Ovarian Cysts
Mirena increases the rate of functional ovarian cysts. These form when a follicle develops but doesn’t fully release an egg, leaving a fluid-filled sac on the ovary. Most cause no symptoms at all and are only discovered incidentally on ultrasound. When they do cause symptoms, it’s typically mild pelvic pain or a feeling of pressure on one side.
The reassuring part: 80% to 90% of these cysts resolve on their own within three months. They rarely require any intervention. A small number can grow large enough to cause sharp pain if they rupture or twist, but this is uncommon. If you get periodic pelvic pain that comes and goes, cysts are a likely explanation.
Skin and Hair Effects
Levonorgestrel has mild androgenic activity, meaning it can stimulate the same receptors as testosterone. In practice, this shows up as acne or hair-related changes in some users. Meta-analyses have found a roughly fivefold increase in acne reports among levonorgestrel IUD users, though the finding didn’t reach statistical significance due to small numbers. If your skin was clear before Mirena and you develop persistent breakouts along the jawline or chin, the hormone is a plausible cause.
Hair loss is less common but documented. A large Finnish study reported hair loss rates of 15.7% among users, though other data puts the figure much lower. A New Zealand monitoring program estimated the cumulative incidence of alopecia at about 0.33%. The wide range likely reflects differences in how hair loss was defined and measured. In most cases, hair thinning is diffuse rather than patchy, and it tends to stabilize or reverse after the device is removed.
Weight Changes
Weight gain is one of the most commonly reported concerns, but clinical data doesn’t support a direct link. A study tracking BMI at two, four, and six months after insertion found no statistically significant difference in body weight. Longer-term observational studies show that Mirena users gain weight at roughly the same rate as the general population over time, meaning age and lifestyle appear to be the primary drivers rather than the device itself.
That said, individual experiences vary, and hormonal shifts can affect water retention, appetite, or body composition in ways that feel real even when average group data doesn’t show a signal. If you’ve gained weight and suspect Mirena, it’s worth tracking other potential factors before attributing it solely to the IUD.
Bone Density
Unlike some other hormonal contraceptives (particularly the injection), Mirena does not cause loss of bone mineral density. Cohort studies have consistently shown no link between long-term use and weakened bones. One isolated case report described low estrogen and bone loss in a 29-year-old after six years of use, but larger studies failed to confirm any pattern. There is no restriction on using Mirena if you’re at risk for low bone density.
Other Reported Effects
Beyond the major categories, meta-analyses have identified statistically significant increases in headaches and breast tenderness among long-term users. These tend to be most pronounced in the first several months after insertion and often diminish as the hormone release rate tapers. Some users also report decreased sex drive, fatigue, or bloating, though these are harder to quantify in controlled studies because they overlap heavily with normal hormonal fluctuations.
What Happens After Removal
Some people experience a cluster of symptoms after Mirena is taken out, sometimes called the “Mirena crash.” Reported symptoms include breast tenderness, headaches, mood swings, fatigue, and reduced interest in sex. The idea is that your body has adapted to a steady supply of levonorgestrel, and removing it creates a temporary hormonal gap while your natural cycle restarts.
This isn’t a formally recognized medical diagnosis, and there’s limited clinical research on its prevalence or duration. But the reports are consistent enough to take seriously. Some people feel back to normal within a few weeks, while others describe recurrent symptoms before each period that persist for several months. If you’re planning removal, it helps to know this adjustment period is possible so you aren’t caught off guard.