An IUD (intrauterine device) is a small, T-shaped device a healthcare provider places inside the uterus to prevent pregnancy. There are two kinds — hormonal and copper — and both are more than 99% effective. Because there's nothing to remember day to day, the IUD is one of the most reliable reversible methods available.
How it works
According to ACOG and the NHS, the two types prevent pregnancy in slightly different ways:
- Hormonal IUD (IUS): releases a small amount of progestogen, which thickens cervical mucus (blocking sperm) and thins the lining of the uterus. It may also reduce ovulation in some people.
- Copper IUD: contains no hormones. The copper changes the environment of the uterus and is toxic to sperm, preventing fertilization.
Both work locally, inside the uterus, which is why side effects tend to be more localized than with methods that circulate hormones throughout the body. Neither device is felt during normal daily life; a short pair of threads sits at the top of the vagina so the device can be checked and later removed.
Hormonal vs. copper: which is which?
| Hormonal IUD | Copper IUD | |
|---|---|---|
| Hormones | Progestogen | None |
| Typical lifespan | ~3–8 years (varies by brand) | Up to about 10 years, with some evidence supporting longer use under a provider's guidance |
| Effect on periods | Often lighter; may stop | May be heavier/crampier, especially early |
| Emergency use | No | Yes — most effective emergency option within 5 days |
The copper IUD doubles as the most effective form of emergency contraception when fitted within 5 days — see the morning-after pill and emergency options. Planned Parenthood notes that once a copper IUD is in place, nothing else is needed, and depending on the brand it can prevent pregnancy for up to about 10 years.
How effective is it?
Both IUD types are over 99% effective. Crucially, their typical-use effectiveness is essentially the same as perfect-use, because there's nothing to forget — no daily pill, no per-act step. That's why long-acting methods outperform the pill in real-world use; compare them in our birth control methods guide or against the other long-acting option in the contraceptive implant explained.
What to expect at the appointment
Anxiety about the fitting is the most common reason people hesitate, so it helps to know the shape of the visit.
- Beforehand, a provider will take a medical history and may offer an STI test, since fitting an IUD while an untreated infection is present is best avoided.
- The fitting itself takes only a few minutes. A speculum is used, the cervix is checked, and the device is passed through the cervix into the uterus. The whole appointment is usually much longer than the procedure.
- Discomfort varies widely. Many people describe strong period-type cramping for a minute or two. Ask in advance about pain relief options — including taking a simple painkiller beforehand and what local anaesthetic the clinic offers.
- Afterwards, cramping and spotting for a few days are normal. Plan a low-key rest of the day if you can, and consider having someone accompany you.
- A follow-up check is usually arranged a few weeks later to confirm the device is correctly placed. The NHS advises a check around 3 to 6 weeks after fitting.
Side effects and what to expect
- First few months: spotting, irregular bleeding, and cramping are common as your body adjusts.
- Hormonal IUD: periods often become lighter or stop; some people notice hormonal side effects, usually mild.
- Copper IUD: periods may be heavier or more painful, particularly at first.
- Settling in: most bleeding changes ease within the first several months. If they don't, that is a reason to review the method — not to assume you must tolerate it.
Who an IUD suits — and who it doesn't
An IUD tends to suit people who want years of protection with nothing to remember, who have found daily or weekly methods hard to keep up with, or who want a highly effective method that is fully reversible. The hormonal IUD often appeals to people with heavy or painful periods; the copper IUD appeals to those who want to avoid hormones entirely — see non-hormonal birth control for the wider hormone-free picture.
It may be a poorer fit if:
- You have an untreated pelvic infection or STI, unexplained vaginal bleeding, or certain differences in the shape of the uterus or cervix — the NHS lists these as reasons an IUD may not be suitable, and a provider will check.
- You may already be pregnant.
- Heavier periods would be difficult for you — in which case a hormonal IUD is usually the better of the two.
- You want a method you can start and stop yourself, since both fitting and removal require a trained provider.
Cost and access
An IUD is fitted by a trained clinician — typically at a general practice, sexual health or family planning clinic, or gynaecology service. In some health systems, including the NHS, contraception including IUD fitting is provided free of charge. Elsewhere it may be covered by insurance, subsidized through public health programmes, or paid for directly. We don't quote prices, because they vary enormously by country and provider. What is broadly true everywhere: the cost is front-loaded into one appointment and then spread across years of use, which often makes an IUD one of the better-value methods over time. Ask a local clinic which services fit IUDs and what support is available.
Other things to know
- Reversible: fertility returns quickly after removal — see getting pregnant after stopping birth control.
- No daily effort: once in place, it works in the background for years.
- Removal is quicker than fitting and can be done at any point, whether you want to change methods or try to conceive.
- No STI protection: the IUD prevents pregnancy only. Use condoms to reduce STI risk.
The bottom line
The IUD is a low-maintenance, highly effective, fully reversible method — hormonal if you'd like lighter periods, copper if you prefer hormone-free (and want an emergency-contraception option). Insertion and the first few months can bring cramping and irregular bleeding, but these usually settle, and the protection then lasts for years with nothing to remember. A provider can help you decide which type fits you; to weigh it against everything else, start with our contraception guide. This article is general education and is not a substitute for individualized medical advice.
