The coil: what it is, how it works & side effects

Reviewed by our clinical team

Interested in switching up your contraception but not sure on your options? If you’re looking for something really low maintenance and very effective, the coil could be just right. 

In this article we’ll look in depth at what the coil is, how it works and side effects some women might experience after getting the coil inserted. 

What is the coil?

The copper coil is another name for the intrauterine device, or IUD. There's also the hormonal coil, also known as the intrauterine system, or IUS. 

The IUD and the IUS are types of long-acting, reversible contraception that are inserted into the womb to prevent pregnancy. The difference is that the IUD uses copper as a contraceptive, which is why it’s sometimes called the copper coil, while the IUS uses hormones, which is why it’s sometimes called the hormonal coil.

Both types are small, T-shaped devices small enough to hold in your palm. The copper coil (IUD) is made with plastic and copper, while the hormonal coil (IUS) contains progestogen, a synthetic version of the hormone, progesterone. 

In addition to being used for regular contraception, the copper coil can also be used as emergency contraception if fitted within five days of unprotected sex. Find out more about the IUD as emergency contraception. 

How does the coil work?

The copper coil works by releasing copper. The copper in the IUD stops sperm and eggs from surviving. It also changes your cervical mucus to stop sperm from reaching an egg.

An IUD may also work by stopping a fertilised egg from implanting in the uterus.

The IUS works by releasing progestogen, which is a synthetic version of the hormone progesterone and also acts as a contraceptive. It thickens the cervical mucus, which makes it more difficult for sperm to move through the cervix, and thins the lining of the womb so an egg is less likely to be able to implant itself.

For some people, it can also prevent the release of an egg each month (ovulation), but most people continue to ovulate.

How long does the coil last?

• The IUD/copper coil lasts for five to 10 years, depending on the type.
• The IUS/hormonal coil last for three to five years, depending on the type. 

How to get the coil fitted

A coil is not something you can fit yourself – it has to be inserted by a trained healthcare professional. The good news is, this service is available for free on the NHS. You can get the coil fitted at contraception clinics, sexual health/GUM clinics and some GP surgeries. 

They will ask you some questions about your health and then will do an internal examination to check the size and position of your uterus. Sometimes they will also check for any STIs. Then they’ll hold your vagina open and put the device through your cervix into your womb. Both types of the coil have small threads that hang from the bottom, through the cervix – these are there so you can check the device is still in place. 

Does the coil hurt?

Getting the IUD or the IUS fitted can be uncomfortable, as the device has to be inserted through the cervix. If you’re worried about the pain beforehand, you can speak to the doctor or nurse about getting a local anaesthetic. 

What symptoms can I expect after I’ve had the coil inserted?

After having the coil inserted you might have:

• Some cramping similar to period pains
• Some light bleeding

You should be able to manage any pain by taking over-the-counter painkillers like ibuprofen and paracetamol.

Potential coil side effects

The main side effect of having the IUD/copper coil fitted is heavier and more painful periods – although this won’t happen for everyone. 

However, because the IUS/hormonal coil releases progestogen, it can cause:

• Headaches 
• Acne 
• Breast tenderness 
• Mood changes 
• Ovarian cysts – this is uncommon 
• Vaginal bleeding and pain – this is uncommon

Risks of the coil

In rare cases, having a coil inserted can lead to a pelvic infection or damage to the womb. If you experience any pain or tenderness in your abdomen, you have a fever, your vaginal discharge changes (e.g. it becomes smelly), or you experience any unusual bleeding you should see your GP.

Sometimes, your coil might move or come out altogether from your womb. You may be able to tell that this has happened if you can’t feel the threads that hang from the bottom of the device.

Lastly, there’s a slightly increased risk of ectopic pregnancy with the IUD and IUS – but this can only happen if they fail as contraception, which is very unlikely. An ectopic pregnancy is when a fertilised egg implants itself outside of the womb, typically this is in the fallopian tubes. 

Does the coil stop periods?

The IUS/hormonal coil can make your periods a lot lighter, shorter and less painful – for some women, periods stop altogether.

However, the IUD/copper coil can have the opposite effect and make your periods heavier, longer and more painful. This won’t happen for all women, and if it does you may find that your periods improve after a few months. 

How effective is the coil at preventing pregnancy?

Both the IUD/copper coil and the IUS/hormonal coil are over 99% effective at preventing pregnancy when positioned correctly. 

Where can I get the coil removed?

You can get your coil removed at the same place where you had it inserted (e.g. a contraception clinic or GP surgery). With both the IUD and the IUS, there’s a risk of pregnancy as soon as it’s been removed. This is why the NHS recommends using additional contraception like condoms for seven days before you have it removed.

Once your coil has been removed you can have a new coil put in or switch to a different type of contraception (e.g. the pill) unless you are trying to get pregnant. 

Other contraceptive options

There are lots of different contraceptive options if the coil isn’t your first choice. 

Combined pill

The combined pill uses synthetic forms of progestogen and oestrogen to prevent pregnancy. You usually take it for 21 day and then have a four or seven-day break, during which you’ll have a withdrawal bleed (which is like a period, but isn’t one).

Progestogen-only pill

Sometimes called the mini pill, the progestogen-only pill, uses a synthetic form of progestogen to prevent pregnancy. You’ll have to take this kind of pill every day, with no break. 

Contraceptive patch or ring

Both the patch and ring are considered ‘combined contraceptives’ because they also use progestogen and oestrogen to prevent pregnancy. The patch is worn on the skin. The ring is inserted into the vagina. 

Contraceptive implant/injection

The implant and injection use artificial versions of progestogen to avoid pregnancy. The implant is a small device inserted into the arm - it can last up to three years. With the injection, you’ll need to have it administered by a clinical around every 13 weeks. 

References

https://www.nhs.uk/conditions/contraception/iud-coil/
https://www.nhs.uk/conditions/contraception/ius-intrauterine-system/
https://www.nhs.uk/conditions/ectopic-pregnancy/