A DIU (also written as 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, with over 99% effectiveness for both types. Once inserted, it works continuously for years without requiring you to do anything, making it one of the easiest contraceptive methods to use. The term “DIU” comes from the Spanish and Portuguese abbreviation (dispositivo intrauterino), while English-speaking countries use “IUD.”
Two Types: Copper and Hormonal
There are two main categories of IUDs, and they work in very different ways. Copper IUDs contain no hormones at all. Instead, a small amount of copper wrapped around the device creates an environment inside the uterus that is toxic to sperm, preventing fertilization. ParaGard is the only copper IUD available in the United States, and it lasts up to 10 years.
Hormonal IUDs release a small, steady dose of a synthetic hormone that thickens cervical mucus (making it harder for sperm to reach an egg), thins the uterine lining, and in some cases suppresses ovulation. Several hormonal brands exist, including Mirena, Liletta, Kyleena, and Skyla. Depending on the specific product, hormonal IUDs last between 3 and 8 years. Mirena and Liletta, two of the most widely used, are now approved for up to 8 years of pregnancy prevention.
How Effective It Is
Both copper and hormonal IUDs are over 99% effective at preventing pregnancy with typical use. That “typical use” number is important because, unlike the pill or condoms, there’s virtually no gap between perfect use and real-world use. You can’t forget to take it or use it incorrectly. Once it’s in place, it works.
What Insertion Feels Like
Getting an IUD inserted is a quick office visit, usually taking just a few minutes for the actual placement. A clinician uses a thin tube to guide the device through the cervix and into the uterus. The experience varies widely from person to person. Some people feel mild cramping similar to a period, while others find it intensely uncomfortable.
Several factors influence how much it hurts, including your age, whether you’ve had pelvic exams before, past trauma, and baseline anxiety levels. The American College of Obstetricians and Gynecologists now recommends that clinicians offer pain management options to every patient, including numbing sprays, topical creams, and cervical nerve blocks. For those who are especially anxious or pain-sensitive, sedation or anesthesia may also be available. You have every right to ask about these options before the procedure and to decide what approach works best for you.
How Each Type Affects Your Period
The copper and hormonal IUDs have nearly opposite effects on menstrual bleeding, which is often a deciding factor when choosing between them.
Copper IUD
Expect heavier, longer periods, especially during the first 3 to 6 months. On average, menstrual blood loss increases by about 50%. Cramping during periods can also worsen. These changes often settle down over time but don’t disappear entirely. A copper IUD will never stop your period.
Hormonal IUDs
Hormonal IUDs generally make periods lighter. Mirena, the highest-dose option, reduces menstrual bleeding by up to 90% within 6 months. Both Mirena and Liletta are also FDA-approved to treat heavy menstrual bleeding. Many users eventually stop getting a period altogether: about 20% of Mirena users have no bleeding after one year, rising to 40% by five years. Lower-dose options like Kyleena and Skyla also lighten periods, though fewer users lose their period completely (23% and 12% at the five-year mark, respectively).
The first few months with any hormonal IUD tend to involve irregular spotting and unpredictable light bleeding. This is normal and typically settles within 3 to 6 months as your body adjusts.
Possible Risks and Complications
Serious complications from IUDs are uncommon, but they do happen. The two main ones to know about are expulsion and perforation.
- Expulsion means the IUD partially or fully slips out of position. This happens in 2 to 10% of users, depending on the type. You can check for proper placement by feeling for the thin strings that hang through the cervix. If the strings feel longer or shorter than usual, or if you can feel the hard plastic of the device itself, contact your provider.
- Perforation occurs when the device pushes through the uterine wall during insertion. This is rare, happening in roughly 1 out of every 1,000 insertions, and typically requires removal of the device.
Common, non-serious side effects depend on the type. Copper IUD users most often report heavier bleeding and stronger cramps. Hormonal IUD users may experience spotting, lighter periods, or the absence of periods, along with occasional headaches or mood changes in the first few months.
Who Should Avoid an IUD
Most people can safely use an IUD, but certain conditions make it a poor fit. Active pelvic infections, unexplained uterine bleeding, certain uterine abnormalities (like large fibroids that distort the shape of the uterine cavity), and cervical or uterine cancer are situations where an IUD is generally not recommended. A copper IUD specifically should be avoided if you have a copper allergy or Wilson’s disease. Your provider will review your medical history before placement to confirm it’s a safe option.
Fertility After Removal
One of the biggest advantages of an IUD is that fertility returns almost immediately after removal. You can start trying to conceive the very first month. A large review of nearly 15,000 women found that contraceptive use, regardless of type or how long it was used, does not delay or reduce fertility. Among the IUD users in that study, 83% became pregnant within 12 months of removal, a rate consistent with the general population trying to conceive.