An IUD, or intrauterine device, is a small T-shaped device placed inside the uterus to prevent pregnancy. It’s one of the most effective forms of birth control available, preventing pregnancy in over 99% of users. Unlike the pill or condoms, an IUD works continuously once placed, lasting anywhere from 3 to 10 years depending on the type.
How an IUD Prevents Pregnancy
All IUDs work by creating an environment inside the uterus that’s hostile to sperm. The device triggers a mild inflammatory response in the uterine lining, which prevents sperm from reaching the fallopian tubes to fertilize an egg. Even in the unlikely event that fertilization occurs, the changes to the uterine lining make it extremely difficult for an embryo to implant and develop.
Beyond that shared mechanism, the two types of IUD work in slightly different ways. Copper IUDs intensify the inflammatory response using copper ions, which are naturally toxic to sperm. Hormonal IUDs release a small, steady amount of a synthetic hormone called progestin, which thickens cervical mucus (creating a barrier to sperm) and thins the uterine lining over time.
Copper vs. Hormonal: The Two Types
There are currently six FDA-approved IUDs on the U.S. market, split into two categories.
Copper IUDs contain no hormones. Paragard, the most well-known, lasts up to 10 years. A newer option, Miudella, is approved for 3 years. Copper IUDs are the only non-hormonal option available, which makes them a good fit if you want to avoid synthetic hormones entirely or if you need emergency contraception (a copper IUD can be inserted within five days of unprotected sex to prevent pregnancy).
Hormonal IUDs release progestin locally into the uterus. The four brands currently available are Mirena (5 to 8 years), Liletta (5 to 8 years), Kyleena (5 years), and Skyla (3 years). They differ mainly in how much hormone they release and how long they last. Because the hormone acts locally rather than circulating through your entire body, the systemic effects are lower than with birth control pills.
Effectiveness Compared to Other Methods
IUDs are among the most reliable contraceptives because they eliminate the possibility of user error. There’s no pill to forget, no ring to replace, no condom to tear. Both copper and hormonal IUDs are over 99% effective with typical use, which is the same as their perfect-use rate.
For comparison, the combined pill is over 99% effective with perfect use but drops to about 91% with typical use, because people miss doses. Condoms fall further, from 98% with perfect use to 82% in real-world conditions. With an IUD, typical use and perfect use are essentially the same, because once the device is in place, there’s nothing for you to remember or manage.
What Insertion Feels Like
Getting an IUD placed is a brief office procedure, usually taking only a few minutes. A clinician performs a pelvic exam to check the size and position of your uterus, then inserts the device through the cervix using a thin applicator tube. You’ll likely feel cramping during the insertion, ranging from mild to sharp depending on your anatomy and pain tolerance.
Pain management has improved significantly. Current CDC recommendations call for a person-centered plan discussed before the procedure, and evidence supports the use of a local anesthetic (a numbing injection near the cervix or a topical numbing gel) to reduce discomfort. If you’re concerned about pain, ask your provider what options they offer. Notably, a medication called misoprostol, once commonly prescribed before insertion, is no longer recommended for routine use because it doesn’t reduce pain and can actually increase cramping and side effects.
After insertion, cramping and spotting are normal for a few days to a few weeks. Most people return to regular activities the same day.
Common Side Effects
The side effects you’ll experience depend largely on which type you get.
With a copper IUD, the most common complaint is heavier periods and stronger cramps, especially in the first few months. This tends to improve over time as your body adjusts. Because there are no hormones involved, you won’t experience hormonal side effects like mood changes or acne.
With a hormonal IUD, the pattern is often the opposite. Many people experience lighter periods and less cramping. Some stop getting periods altogether while the device is in place. This isn’t harmful; it simply means the uterine lining has thinned enough that there’s very little to shed each month. Irregular spotting is common in the first three to six months before your cycle settles into a new pattern.
Risks to Know About
Serious complications from IUDs are rare, but they exist. The two main ones are expulsion (the device partially or fully slipping out of place) and perforation (the device pushing through the uterine wall).
Uterine perforation is uncommon. A large study published in The Lancet found that the five-year rate of perforation was about 0.29% for people who weren’t recently postpartum. For those who had recently given birth, particularly while breastfeeding, the rate was higher at roughly 1.37%. Most perforations are identified and managed without lasting harm, but it’s one reason providers schedule a follow-up visit after insertion to confirm the device is properly positioned.
IUDs do not increase your long-term risk of pelvic infections. However, there is a slight risk of infection in the first few weeks after placement, which is why providers may screen for sexually transmitted infections before or at the time of insertion.
Who Shouldn’t Get an IUD
Most people with a uterus can safely use an IUD, but certain conditions make placement inadvisable. These include a current pelvic infection or untreated sexually transmitted infection, unexplained vaginal bleeding that hasn’t been evaluated, certain uterine abnormalities that distort the shape of the cavity, and cervical or endometrial cancer awaiting treatment. Pregnancy is also a clear contraindication. If you have any of these conditions, your provider will discuss alternative options.
Benefits Beyond Birth Control
Hormonal IUDs have an FDA-approved use beyond contraception: treating heavy menstrual bleeding. The progestin released by the device thins the uterine lining, which directly reduces menstrual blood flow and cramping. For people who deal with debilitating periods, a hormonal IUD can be a meaningful quality-of-life improvement, sometimes reducing bleeding enough that periods become barely noticeable or stop entirely.
This dual purpose makes hormonal IUDs a common recommendation for people with heavy periods who also want reliable contraception, or even for those who aren’t concerned about pregnancy but need relief from excessive bleeding.
Fertility After Removal
One of the biggest advantages of an IUD is that fertility returns almost immediately after removal. Unlike some other hormonal methods that can delay ovulation for weeks or months, removing an IUD restores your natural cycle right away. You can attempt pregnancy the very first month after removal.
A 2018 review of studies found that 83% of former IUD users were able to get pregnant within 12 months of removal, a rate consistent with the general population trying to conceive. The device has no lasting effect on fertility regardless of how many years it was in place.