What Is a Hormonal IUD? Types, How It Works & Risks

A hormonal IUD is a small, T-shaped device placed inside the uterus that releases a low dose of a synthetic progestin called levonorgestrel directly into the uterine lining. It prevents pregnancy primarily by thickening cervical mucus so sperm cannot reach an egg, while also thinning the uterine lining. Several versions exist with different hormone loads and durations, but they all share the same core mechanism and rank among the most effective reversible contraceptives available, with failure rates comparable to surgical sterilization.

How the Device Works

The hormonal IUD sits inside the uterus and steadily releases levonorgestrel from a silicone reservoir that surrounds its vertical stem. The drug is embedded in a polydimethylsiloxane (silicone) core, and a rate-controlling silicone membrane wraps around it, allowing a controlled daily dose to diffuse into the surrounding tissue.¹ Because the hormone acts locally rather than circulating through the entire body at high concentrations, side effects tend to be milder than those seen with systemic hormonal methods like pills or injections.

The contraceptive effect comes from several overlapping changes. The most important is what happens to cervical mucus. In a study comparing IUD users with controls, none of the hormonal IUD users showed any sperm penetration through cervical mucus, compared with roughly two-thirds of controls whose mucus allowed normal sperm transport.² Essentially, the device turns cervical mucus into a barrier that sperm cannot cross. Beyond this, levonorgestrel thins the endometrial lining, making it less hospitable for implantation, and in some users partially suppresses ovulation, though ovulation still occurs in many cycles.

Types of Hormonal IUDs

All hormonal IUDs on the market release the same hormone, levonorgestrel, but they differ in how much they contain and how long they last. In the United States, four branded products are available. The highest-dose versions contain 52 mg of levonorgestrel and are approved for up to five years of use. These are the most studied and have the broadest range of approved uses, including not just contraception but also treatment of heavy menstrual bleeding and endometrial protection during hormone replacement therapy.³ A mid-dose version holds 19.5 mg of levonorgestrel and is approved for up to five years of contraception. The smallest version contains 13.5 mg and is approved for three years.

The physical frames also differ slightly. The lower-dose devices have a narrower inserter tube and a smaller T-frame, which was designed with adolescents and people with smaller uteri in mind. In practice, though, providers fit all versions to a wide range of patients. The choice between them often comes down to whether a person wants the additional non-contraceptive benefits that come with the higher dose, how long they want protection to last, and how they feel about the likelihood of lighter periods or no periods at all, which is more common with the 52 mg devices.

Effectiveness

The hormonal IUD is one of the most reliable reversible contraceptives. Its failure rate is often described as comparable to sterilization.⁴ A meta-analysis of 20 trials found that hormonal IUDs were associated with a substantially lower risk of pregnancy than copper IUDs.⁵

There is also evidence that the 52 mg device continues to prevent pregnancy well beyond its five-year label. A systematic review found that in years six and seven after insertion, the pregnancy rate remained extremely low, at roughly 0.02 to 0.03 per 100 person-years.⁶ This has led some professional organizations to consider extended use guidelines, though the labeled durations remain the official recommendation.

What Happens to Your Period

Changes in menstrual bleeding are the single most noticeable effect of a hormonal IUD, and also the most common reason people either love or dislike the device. In the first few months, irregular spotting and light bleeding between periods are common. Over time, bleeding tends to decrease significantly. A systematic review and meta-analysis found that very few users experienced no periods at all during the first 90 days, but by the end of the first year, about one in five had at least one 90-day stretch without a period.⁷ A separate study reported similar numbers: among new users of the 52 mg device, about 17% had no period by the nine-month mark.⁸

For many users this is a welcome change, but the unpredictable spotting in the first three to six months can be frustrating. It helps to know that the pattern generally settles. In that same study, fewer than 2% of women discontinued during the first year because of bleeding irregularities, and none stopped because their periods disappeared.⁸ The absence of periods on a hormonal IUD is not a sign of something going wrong. The lining simply becomes too thin to build up and shed. Fertility is not affected.

How It Compares to a Copper IUD in Practice

The copper IUD and the hormonal IUD sit in the same category of long-acting reversible contraception, but the day-to-day experience of using them is quite different. In a comparative study tracking bleeding patterns over 12 months, heavy bleeding was reported by about 42% of copper IUD users at three months but only about 10% of hormonal IUD users. By 12 months, heavy bleeding persisted in about 23% of copper users compared to under 5% in the hormonal group, while about 44% of hormonal IUD users had no period at all.⁹ A large meta-analysis confirmed the pattern: hormonal IUDs carried a lower risk of heavy bleeding and painful periods than copper devices, but a much higher chance that users would stop using the device specifically because of absent periods.⁵

The copper IUD uses no hormones, which appeals to people who want to avoid any hormonal method. But for anyone whose heavy or painful periods are a major concern, the hormonal IUD often addresses two problems at once.

Non-Contraceptive Benefits

One of the reasons the hormonal IUD has become so widely used is that it does more than prevent pregnancy. Its effect on the uterine lining makes it a front-line treatment for heavy menstrual bleeding. In a clinical study of women with documented heavy periods, the 52 mg device reduced blood loss by a median of about 93% within three menstrual cycles and roughly 98% by six cycles.¹⁰ A benefit-risk review concluded that the hormonal IUD reduced menstrual blood loss more effectively than oral medications like tranexamic acid, oral progestins, or combined oral contraceptives, and performed comparably to endometrial ablation surgery.¹¹ Cochrane reviews have reported reductions of up to 90% in menstrual blood loss, with improvements in period pain as well.¹²

The device has also shown real benefits for endometriosis-related pain. A review of studies in women with endometriosis, chronic pelvic pain, and adenomyosis found consistent improvements in pelvic pain, painful periods, and menstrual bleeding, with some studies also showing a reduction in uterine volume in adenomyosis patients.¹³ A randomized trial found the IUD performed as well as a GnRH analogue injection for treating endometriosis-related chronic pelvic pain, with the added advantage of not causing the estrogen-depleted state that comes with GnRH therapy.¹⁴ A Cochrane review of postoperative use found that the IUD significantly reduced the return of painful periods compared with no treatment after surgery.¹⁵

Risks and Complications

The hormonal IUD is considered very safe, but no medical device is without risk. The complications that get the most attention are uterine perforation, expulsion, infection, and ectopic pregnancy.

Perforation

Uterine perforation, where the device pushes partially or fully through the uterine wall, is the most serious but also the rarest complication. In a large study of over 326,000 IUD insertions, the five-year cumulative risk of perforation was about 0.3% for people who were not in the postpartum period at the time of insertion.¹⁶ The risk was higher when the IUD was placed during the postpartum window, particularly between four days and six weeks after delivery, when the risk was roughly seven times that of a non-postpartum insertion.¹⁷ Breastfeeding at the time of insertion also modestly increased the risk. An earlier European surveillance study found perforation rates of about 1.4 per 1,000 insertions for hormonal IUDs and 1.1 per 1,000 for copper devices, with breastfeeding carrying a six-fold increase in risk regardless of IUD type.¹⁸ Despite these numbers, researchers have emphasized that perforation remains very rare in absolute terms at every clinical time point.

Expulsion

Expulsion, where the device partially or fully slides out of the uterus on its own, is more common. One large study found a 36-month cumulative expulsion rate of about 10% for both hormonal and copper IUDs.¹⁹ Younger age was a strong predictor: adolescents aged 14 to 19 had roughly double the expulsion risk compared with older users. A diagnosis of heavy menstrual bleeding was the single strongest risk factor for expulsion in another large analysis, while higher body weight and higher parity also contributed.²⁰ If the device partially expels, it no longer provides reliable protection and needs to be removed.

Infection

There was once a widespread belief that IUDs caused pelvic inflammatory disease. Research has largely put this concern to rest. A literature review found the risk of PID among IUD users to be very low.²¹ A systematic review found that any elevated PID risk is tied to having a pre-existing sexually transmitted infection at the time of insertion, not to the device itself. Even among women who had chlamydia or gonorrhea at insertion, the absolute risk of PID was low, in the range of 0 to 5%.²² This is why STI screening around the time of insertion is standard practice, not because the device is inherently risky but because inserting anything through the cervix can introduce existing bacteria upward.

Ectopic Pregnancy

Because the hormonal IUD is so effective at preventing pregnancy overall, the absolute rate of ectopic pregnancy in users is very low. However, when a pregnancy does occur with the device in place, there is a higher-than-normal chance it will be ectopic, meaning it implants outside the uterus. A recent study published in NEJM Evidence found that ectopic pregnancy rates varied by device dose. At one year, the rate was lowest with the 52 mg device (0.04 per 100 person-years) and highest with the 13.5 mg device (0.18 per 100 person-years).²³ A JAMA study found that compared with other hormonal contraceptives, all three dose levels of the levonorgestrel IUD were associated with higher adjusted ectopic pregnancy rates, with the smallest device carrying the highest relative risk.²⁴ This does not mean the IUD causes ectopic pregnancies. Rather, the device prevents uterine pregnancies so effectively that the very small number of pregnancies that do occur are disproportionately ectopic. Anyone with a positive pregnancy test while using a hormonal IUD should seek medical evaluation promptly.

What Insertion Feels Like

Insertion is a brief office procedure that usually takes under five minutes. A clinician places a speculum, cleans the cervix, and uses a thin inserter tube to guide the IUD through the cervical canal into the uterus. Most people feel a sharp cramp during the moments the device passes through the cervix and is released. Pain levels vary widely. In a randomized trial among adolescents and young women, those who received a paracervical nerve block (a local anesthetic injected near the cervix) reported a median pain score of 30 out of 100 during insertion, compared with about 72 in the group that received no real block.²⁵ A similar trial in nulliparous women (those who had never given birth) also found that a paracervical block significantly reduced pain during placement and for the five minutes afterward.²⁶

If you are concerned about pain, it is reasonable to ask your provider about a paracervical block before the procedure. Some clinics also offer oral pain medication beforehand or use cervical-softening agents, though evidence for those approaches is more mixed. Cramping and light spotting in the hours and days after insertion are normal.

Postpartum Insertion Timing

Getting an IUD placed soon after having a baby is convenient and avoids the gap in contraception that often happens when people wait for a follow-up visit. But the timing involves a trade-off. A systematic review and meta-analysis found that immediate postpartum placement (within 10 minutes of placental delivery) had an expulsion rate around 10%, compared with about 2% when the IUD was placed at four weeks or later.²⁷ Vaginal delivery also carried a higher expulsion risk than cesarean delivery for early placements. Another large study found the lowest expulsion rate among those who had the IUD placed between six and 14 weeks postpartum, while the highest rate was for insertions in the first three days.²⁸

For many people, the trade-off is worth it. If you get the device placed right after delivery and it stays in place, you leave the hospital with reliable long-term contraception already working. If it expels, you need a replacement, but you are no worse off than if you had waited. This is a conversation to have with your provider before delivery, not something you need to decide in the moment.

Return to Fertility After Removal

A common concern is whether years of having a hormonal IUD will delay the ability to get pregnant afterward. The evidence is reassuring. In a study comparing conception rates after IUD removal, about 79% of former hormonal IUD users conceived within 12 months, and roughly 87% within 24 months. Those rates were statistically indistinguishable from women who had used a non-hormonal copper IUD.²⁹ Nearly all of the pregnancies occurred within the first year, and the vast majority ended in live births. The researchers noted that despite the endometrial suppression that occurs during use, the uterine lining recovers quickly and normal ovulation resumes promptly.

A more recent pilot study confirmed this finding: pregnancy rates at 12 months were similar between former IUD users and women who had not been using an IUD, with no measurable delay in time to pregnancy.³⁰ If you are planning to try for pregnancy, you can have the device removed and start trying immediately without a waiting period.

Acne and Other Hormonal Side Effects

Because the hormonal IUD delivers a progestin without any estrogen, it can sometimes unmask or trigger skin and hair changes that estrogen-containing methods like the combination pill tend to suppress. A review in the dermatology literature noted that progestin-only methods, including hormonal IUDs, have a tendency to trigger or worsen acne, unwanted hair growth, and hair thinning.³¹

This is especially relevant for people switching from a combination pill to a hormonal IUD. A prospective study found that women who had been on combined hormonal contraception before getting a 52 mg IUD were more likely to report acne in the first year than those who had not been using hormones. At one year, about 16% of former pill users reported acne, compared with about 11% of those who were not using any hormonal method beforehand.³² Other side effects like mood changes, headaches, and breast tenderness were reported on fewer than 3% of days tracked during the first six months, making them uncommon at the population level, even if they can be noticeable for individual users.

The takeaway is that the hormonal IUD is not the same as the pill when it comes to skin. If your combination pill was keeping your acne under control, switching to a hormonal IUD may let those breakouts return. This is not a new problem the IUD creates; it is the loss of the estrogen-driven acne suppression the pill was providing. Talking through your skin history with your provider before switching can help set expectations.

1
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2
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3
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4
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5
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6
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7
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8
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9
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10
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11
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12
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13
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14
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15
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16
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17
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18
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19
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20
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21
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22
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23
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24
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25
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26
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27
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28
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29
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30
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31
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32
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