An IUD (intrauterine device) is a small, T-shaped device placed inside the uterus to prevent pregnancy. It’s one of the most effective forms of reversible birth control available, with a typical-use failure rate of about 1.4% in the first year. There are two types: hormonal IUDs that release a small amount of progestin, and one non-hormonal option that uses copper instead.
Hormonal vs. Copper: Two Different Approaches
Five IUD brands are currently available, and the biggest distinction is whether they use hormones or copper to prevent pregnancy.
Four brands release a hormone called levonorgestrel (a type of progestin) directly into the uterus. They differ mainly in how long they last:
- Mirena: up to 8 years
- Liletta: up to 8 years
- Kyleena: up to 5 years
- Skyla: up to 3 years
The fifth option, Paragard, contains no hormones at all. It’s wrapped in copper wire and protects against pregnancy for up to 12 years, making it the longest-lasting IUD on the market. It’s also the only non-hormonal IUD available.
How Each Type Prevents Pregnancy
Hormonal IUDs work in three ways at once. They thicken the mucus in the cervix so sperm can’t easily reach an egg. They thin the uterine lining, making it less hospitable. And they partially suppress ovulation, meaning your ovaries release eggs less frequently. This combination is what makes them so reliable.
The copper IUD takes a completely different approach. Copper ions dissolve into the fluids of the reproductive tract and create an environment that’s toxic to sperm, damaging their ability to move and survive. This effect reaches the entire genital tract, not just the uterus, which significantly reduces the chances of fertilization.
How Effective IUDs Actually Are
IUDs are among the most effective contraceptives available. In typical use, about 1.4 out of every 100 people using an IUD will become pregnant in the first year. U.S. clinical data puts that number even lower, at roughly 0.8%. For context, the pill and male condoms each have typical-use failure rates around 5 to 6% globally, and methods like withdrawal and fertility awareness hover around 13 to 14%.
What makes IUDs stand out is how well they hold up over time. After three years of use, the cumulative failure rate for IUDs is just 2.1%. Compare that to the pill at 15.1% or male condoms at 16% over the same period. Because an IUD works without you needing to remember anything, there’s almost no gap between “perfect use” and real-world use.
What Insertion Feels Like
Getting an IUD placed is a brief in-office procedure that typically takes only a few minutes. Your provider uses a speculum (the same tool used during a Pap smear), then measures the depth of your uterus with a thin instrument called a sound. Most uterine cavities measure between 6 and 9 centimeters. The IUD is then loaded into a slim inserter tube and guided into place. Afterward, the strings are trimmed to about 3 to 4 centimeters so they hang just inside the cervical opening.
The honest reality is that insertion can hurt. The most intense discomfort usually comes during two moments: when the cervix is grasped with a stabilizing instrument and when the device passes through the cervical opening. The sensation is often described as a sharp cramp. The CDC’s 2024 guidelines recommend that providers discuss pain management options before the procedure and create a plan based on each patient’s preference. A numbing injection near the cervix (a paracervical block) or topical numbing gel can help reduce pain. Over-the-counter pain relievers taken beforehand are commonly suggested, though clinical evidence on their effectiveness is mixed. A follow-up visit is usually scheduled 4 to 6 weeks later to confirm the IUD is still in the right position.
Changes to Your Period
The two types of IUDs affect periods in opposite ways, and this is often a deciding factor when choosing between them.
Hormonal IUDs tend to make periods lighter over time. Some people stop getting a period altogether. In the first three months, only about 0.2% of users experience no bleeding at all, but by the end of the first year, roughly 20% have at least one stretch of 90 days without any bleeding or spotting. By cycle six after insertion, about 19% of users report no bleeding and another 29% report only light spotting. For many people, this is a welcome side effect rather than a concern.
The copper IUD, on the other hand, often makes periods heavier, longer, or more painful, particularly in the first several months. For most people, this settles down over time, but heavier flow is a known trade-off for choosing the hormone-free option.
Beyond Birth Control
Hormonal IUDs have a well-established role in treating heavy menstrual bleeding. The higher-dose versions (Mirena and Liletta, which contain 52 milligrams of levonorgestrel) are considered the most effective treatment option for this condition. In clinical trials, participants saw a median blood-loss reduction of about 93% by the third cycle and nearly 98% by the sixth cycle. Treatment was successful in roughly 82% of participants regardless of body weight or whether they had previously given birth.
Possible Risks and Complications
Serious complications from IUDs are uncommon, but they do happen. The two main concerns are expulsion (the device partially or fully slipping out) and perforation (the device pushing into or through the uterine wall).
Expulsion is the more common issue. About 2.3% of IUDs are expelled within the first year, and the five-year cumulative rate is around 4.6% for people who weren’t recently postpartum. You might notice expulsion if you feel the device, see it come out, or experience unusual cramping or bleeding. This is why checking for the strings periodically matters.
Perforation is rare. The one-year rate is about 0.2%, and the five-year rate is roughly 0.3% for people who didn’t recently give birth. Both expulsion and perforation are more likely when the IUD is placed soon after delivery. For insertions done within the first three days postpartum, the five-year expulsion rate rises to about 11%, and perforation risk also increases, particularly for people who are breastfeeding.
Who Can and Can’t Use an IUD
Most people can safely use an IUD, including those who have never been pregnant. There are, however, some situations where placement isn’t appropriate. You shouldn’t get an IUD if you’re currently pregnant, have an active pelvic infection or untreated sexually transmitted infection, or have unexplained vaginal bleeding that hasn’t been evaluated. Certain uterine abnormalities that distort the shape of the uterine cavity can also make placement impossible. Endometrial or cervical cancer awaiting treatment is another contraindication.
If your uterus measures less than 6 centimeters deep during the sounding step, the device typically won’t be placed. This is determined at the time of the procedure, so it’s not something you’d necessarily know beforehand.
Removal and Fertility After an IUD
An IUD can be removed at any time, not just when it expires. Removal is generally quicker and less uncomfortable than insertion. Your provider grasps the strings and pulls the device out through the cervix, and the flexible arms of the T fold down as it exits. Fertility returns rapidly after removal, often within the first menstrual cycle, because IUDs work locally rather than suppressing your entire hormonal system.