How it works
The device is made of plastic and copper. Copper is toxic to sperm and eggs and changes the fluid in the uterus and fallopian tubes, which stops sperm from fertilizing an egg. It may also stop a fertilized egg from implanting.
People who want very effective, long-lasting contraception without hormones, or who need emergency contraception and want ongoing protection afterward.
How effective is it?
Typical use
Over 99%
In real life fewer than 1 in 100 people get pregnant in a year.
Perfect use
Over 99%
About 0.6 in 100 when used exactly as directed every time.
See how it ranks against every method in the effectiveness chart.
How to use it
See a doctor, nurse, or sexual health or family planning clinic; you may be checked for infections first.
A trained clinician places the device through the vagina and cervix into the uterus; fitting takes a few minutes and can be uncomfortable, so ask about pain relief.
It works as soon as it is fitted, at any point in your cycle, so no backup method is needed.
Two thin threads hang into the top of the vagina; you can learn to check them to make sure it is still in place.
Have it removed or replaced by a clinician when it is due (5 or 10 years depending on the type), or any time you want to stop.
Pros and cons
Advantages
- Over 99% effective and works immediately after fitting.
- Contains no hormones, so it avoids hormonal side effects.
- Lasts 5 to 10 years from one fitting, depending on the type.
- Can be used as emergency contraception, and is the most effective emergency method.
- Can be used while breastfeeding.
- Fertility returns quickly after removal.
Disadvantages
- Does not protect against sexually transmitted infections (STIs); use condoms as well for that.
- Periods may become heavier, longer, or more painful, particularly in the first months.
- Fitting needs a clinician and can be painful for some people.
- Small risks at fitting, including infection in the first few weeks, the device coming out, and rarely perforation of the uterus.
Effect on periods: Periods may become heavier, longer, or more painful, especially in the first 3 to 6 months.
Possible side effects
- Heavier or longer periods
- More painful periods or cramping
- Spotting between periods, especially early on
- Cramping or discomfort for a day or two after fitting
Who it may not suit
A clinician checks your medical history before you start. This list is not complete.
May not be suitable if
- You have a current pelvic infection or untreated STI.
- You have unexplained vaginal bleeding that has not been checked.
- You already have very heavy or painful periods.
- You have certain conditions affecting the shape of the uterus or cervix, or cancer of the cervix or uterus.
- You have a copper allergy or Wilson's disease.
Get medical help if
- You cannot feel the threads, they feel different, or you can feel the hard part of the device.
- You have severe lower tummy pain, fever, or unusual smelly discharge, especially in the first weeks after fitting.
- You think you might be pregnant; pregnancy with an IUD is rare but needs checking quickly because of a higher chance of ectopic pregnancy.
- Your bleeding is very heavy or you feel dizzy, tired, or short of breath, which can be signs of anemia.
Frequently asked questions
Can a copper IUD be used as emergency contraception?
Yes. It can be fitted within 5 days of unprotected sex (or within 5 days of the earliest likely ovulation date) and is the most effective form of emergency contraception. It then continues as regular contraception.
Does the copper IUD make periods worse?
It often makes periods heavier, longer, or more painful, especially in the first 3 to 6 months. For many people this improves over time; a clinician can suggest treatment if it does not.
How long does a copper IUD last?
Depending on the type, 5 or 10 years. The common US device is licensed for 10 years, and UK guidance allows some people who have one fitted at 40 or older to keep it until after menopause; ask your clinician.
Does the copper IUD have any hormones?
No. It works through copper alone, so your natural cycle continues and you still ovulate.
Can a copper IUD cause weight gain?
There is no good evidence that the copper IUD causes weight gain, because it contains no hormones.
Sources
Reviewed 1 November 2026. We link to the guidance itself so you can check it.