Reviewed July 2019

The truth about IUDs and side effects

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Choosing a type of contraception is an important and often quite stressful decision that many women will have to make during their reproductive lifetime. With such a variety of methods out there it can be difficult to decide, especially when it is hard to find someone who will tell you honestly what side effects you might experience.

For those looking for a method of long-term but non-hormonal contraception, the copper intrauterine device, also know as the copper IUD or copper coil, may look to be an attractive option. But because it doesn’t contain hormones, does that mean you won’t experience side effects? And are there any particular benefits to using a non-hormonal form of contraception? Here, we look at all the risks and benefits, to help you decide if it’s the right type of contraception for you.

What is the copper coil?

The copper coil is small T-shaped device made of plastic and copper, which is designed to sit in the womb and alter its biological and chemical environment. It works by releasing small amounts of copper into the uterus, which alters the biochemical makeup of the cervical mucus and, in turn, reduces the chance of egg or sperm survival.1

The copper prevents fertilisation in a number of ways. Firstly, it hinders egg implantation.2 This is because the presence of the copper creates a local inflammatory reaction within the lining of the womb, making it resistant to implantation.3

Secondly, it hampers the sperm’s progress and reduces its movement, while also reducing the quality of the sperm itself, although it is not clear exactly why this occurs.4,5 Research suggests that as well as hindering egg implantation, the sterile inflammatory reaction created by the IUD also sets off a chain of reactions that are ultimately toxic to sperm. Copper increases the extent of this inflammatory reaction and also seems to affect the sperm’s ability to move.6 Other studies have shown that in women with a copper IUD inserted, the tails were separated from the bodies of the sperm cells.7

Once placed, the coil can be left in for a number of years and is estimated to be 99% effective when inserted properly.8 It is inserted by a trained nurse or doctor in a process that usually takes from 15 to 20 minutes and may be mildly uncomfortable. It is inserted through the cervix and into the uterus, sitting high in the womb. The copper coil doesn’t protect against sexually transmitted disease, and also carries a small risk of infection, ectopic pregnancy, and some other side effects.9

How is the copper coil different from hormonal intrauterine systems (IUSs)?

The differences between the copper and hormonal coil systems are in their workings and side effects. Hormonal coils, such as the Mirena coil, secrete synthetic progesterone. This alters your body’s natural rhythm, convincing it that you are already pregnant. By releasing progesterone, sometimes called the ‘pregnancy hormone’, the womb undergoes changes that prepare for implantation of the egg and pregnancy. At the same time, the ovary itself is signalled to stop maturing or releasing any more eggs, taking advantage of a complex hormonal feedback loop. This means, in practice, that the ovary should not release an egg at all, and without an egg there is no chance of fertilisation.

The copper coil lasts longer than the hormonal varieties, and avoids some of the side effects seen with hormones.

But are there side effects with the copper coil?

As with any medical treatment, there can be some side effects with the copper coil.10 Short-term side effects include spotting and cramps for a number of days after insertion. Heavier periods are common but should settle — menstrual changes are common during the first 3-6 months after insertion.11 Longer-term side effects include irregular bleeding, usually up to six months. Although the specific mechanism leading to increased bleeding and cramps is under review, there is evidence prostaglandins may have a role.12

Prostaglandins are lipids (fats) made at sites of tissue damage or infection and are also involved in controlling the menstrual cycle. They cause inflammation and pain as a natural part of your body’s healing process. As part of inflammatory reactions, prostaglandins can increase blood flow within a region, and specifically within the womb. They also trigger contractions of uterine muscles, causing cramping and pain.13

Other side effects of the copper coil can include backache, and it is worth noting that up to 50% of women discontinue use of the copper coil within five years, most commonly due to either bleeding or cramps.14 Other symptoms, such as vaginal discharge, pain during intercourse, and feeling generally unwell might indicate another problem such as infection, and if you are experiencing these you should go and seek the advice of your doctor.

Although hormones are not affected by the copper coil, the decision to use contraception can also bear emotional weight. However, any anecdotal reports of mood swings are unlikely to be due to the coil itself. Finally, there is some worry among potential users about copper toxicity, but current research suggests that although some copper may be absorbed by the blood, this is unlikely to reach toxic levels.15

Are there any risks?

As with any medical procedure, there are small risks. During insertion there is a 1-2/1000 risk of perforating the uterine lining.16 If you are in a large amount of pain post-insertion this may be an indication of perforation and you should contact your GP. The coil is 99% effective, which means that 1/100 couples using it for a year would fall pregnant. The risk of expulsion of the device is around 1/20, and is the most common in the first year of use.17

Although overall risk of ectopic pregnancy is lower for those using the coil when compared to those not using it, if a woman using the coil gets pregnant it is more likely to be ectopic than if she wasn’t using it. The amount this risk is said to increase varies between studies, with some studies reporting that up to half of pregnancies occurring on the coil were ectopic.18 This is when the egg implants outside of the womb and carries a significant medical risk.

A more serious risk is infection. Introduction of bacteria into the womb can come before, during, or after insertion. For this reason, it is important to have yourself checked before using the coil, and those with a copper coil inserted should watch for symptoms such as discharge, pain outside of or during sex, nausea, fever or feeling generally unwell. The rate of infection is around 0.97% in the first 20 days after insertion, then 0.14% after that.19

Untreated infections can lead to pelvic inflammatory disease and infertility. One episode of untreated pelvic inflammatory disease carries around an 8% risk of infertility, whereas three or more untreated episodes carry up to a 40% risk.20

A doctor will not insert the coil if you have a current sexually transmitted disease or pelvic infection.

When should I see my doctor?

Although side effects are common, that doesn’t mean you can’t seek help. If you are having trouble tolerating them, visit your GP. You should see your doctor if you have any of the symptoms that indicate infection. If you are concerned that you may be pregnant, see you doctor immediately. If you are in any doubt as to whether the symptoms you have are normal and/or temporary, it is always safer to see your doctor.

Last updated July 2019
Next update due July 2021

Dr Benjamin Janaway, MBChB BMedSci

Ben is a doctor and writer, and is chief commissioning editor of TrustedMedicine, and a health politics journalist at The Canary. His background is in medicine, and he trained at Sheffield University before undertaking further training at Derriford Hospital, Plymouth. His interests include neurology, evolutionary biology, anthropological psychology, and cosmology. He will be undertaking a masters in translational neuroscience next year.

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  1. Kaneshiro, B., and Aeby, T., ‘Long-term safety, efficacy, and patient acceptability of the intrauterine Copper T-380-A contraceptive device’,  Int J Womens Health, vol. 2, 2010, pp. 211-220.
  2. Wilcox, A.J., et al., ‘Urinary human chorionic gonadotropin among intrauterine device users: detection with a highly specific and sensitive assay’, Fertil Steril, vol. 47, 1987, pp. 265–269.
  3. Ortiz, M.E., et al., ‘Mechanisms of action of intrauterine devices’, Obstet Gynecol Surv, vol. 51, suppl. 12, 1996, pp.S42-51.
  4. Stanford, J.B., and Mikolajczyk, R.T., ‘Mechanisms of action of intrauterine devices: update and estimation of postfertilization effects’, Am J Obstet Gynecol, vol. 187, 2002, pp. 1699–1708.
  5. Mishell Jr, D.R., ‘Intrauterine devices: mechanisms of action, safety, and efficacy’, Contraception, vol. 58, suppl. 3, 1998, pp. 45S–53S.
  6. Goldman, M.B., et al., Women and Health, Academic Press (Elsevier), 2nd edn., China, 2013, p 228
  7. Keller, S., ‘IUDs Block Fertilization’, Family Health International, Winter 1996, vol. 16, no. 2 
  8. NHS Choices Health A-Z, ‘IUD (Intrauterine Device)’, [website], 2015,, (accessed 28 July 2019).
  9. Ibid.
  10. FSRH, Intrauterine contraception: Clinical effectiveness unit, updated October 2015, [online], (accessed 29 July 2019)
  11. NICE, ‘Contraception – IUS/IUD’, Clinical Knowledge Summary, National Institute for Health and Care Excellence, May 2019, [online]!scenario:1 (accessed 28 July 2019) 
  12. Roy, S., and Shaw Jr, S.T., ‘Role of Prostaglandins in IUD-Associated Uterine Bleeding – Effect of a Prostaglandin Synthetase Inhibitor (Ibuprofen)’, Obstetrics and Gynecology, vol. 58, no. 1, 1981, pp. 101-106.
  13., Period pain: overview, Institute for Quality and Efficiency in Health Care, 2006. Accessed online: (accessed 28 July 2019)
  14. Kaneshiro, B., and Aeby, T., ‘Long-term safety, efficacy, and patient acceptability of the intrauterine Copper T-380-A contraceptive device’,  Int J Womens Health, vol. 2, 2010, pp. 211-220
  15. Imani, S., et al., ‘Changes in copper and zinc serum levels in women wearing a copper TCu-380A intrauterine device’, Eur J Contracept Reprod Health Care, vol. 19, no. 1, 2013, pp. 45-50. 2013.
  16. FSRH, Intrauterine contraception: Clinical effectiveness unit, updated October 2015, [online], (accessed 28 July 2019)
  17. Ibid.
  18. Ibid,
  19. Kaneshiro, B., and Aeby, T., ‘Long-term safety, efficacy, and patient acceptability of the intrauterine Copper T-380-A contraceptive device’, 2010, pp. 211-220.
  20. Centres for Disease Control and Prevention, Pelvic Inflammatory Disease (PID) detailed fact sheet, January 2017, [online] (accessed 28 July 2019)

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