How does the copper IUD work?

The copper intrauterine device (IUD), better known as the copper coil, is one of the most effective types of birth control out there, preventing pregnancy up to a whopping 99.9% of the time. 

So why aren’t we all rushing in droves to get our coils fitted? 

Well, like lots of different types of birth control (and generally most things female health) there are many misconceptions about the IUD. These range from the cautious, ‘isn’t the insertion process really painful?’ to the downright ridiculous ‘don’t IUDs cause infertility?’.  

But as always, we’re here to help you decipher the science from pseudoscience. Here’s (just about) everything you need to know about the copper IUD—including how it prevents pregnancy, how it’s inserted and just about every pro and con we could think of. 

Let’s get to it...

What is the copper intrauterine device (IUD)?

IUDs are a form of long-acting reversible contraception (LARC). There are two types of IUDs, the progestogen-only hormonal IUD, and the non-hormonal copper IUD. 

Both IUDs are small flexible T-shaped devices about 1”x1” in diameter and <1g in weight. The hormonal IUD is made of plastic, but the copper IUD—(yep, you guessed it) is made of copper. Each of its arms is wrapped in a thin copper wire and it sports a very dandy copper collar. 

There are a few different copper IUD brands on the market but only one that’s available in the U.S., ParaGard. It was approved by the FDA in 1984 and has been available in the US since 1988.

IUDs have a bad rep because of their insertion and removal process (which we’ll come to in a moment), but they’re actually the 3rd most used birth control method globally, with over 150 million people worldwide using the copper coil (1).

How is an intrauterine device inserted?

An IUD will need to be inserted and removed by a healthcare practitioner (we repeat, don’t try this one at home). 

The insertion process for IUDs is often a big sticking point and has gained a lot of traction recently because of the, often, lack of pain medication offered during the procedure. 

But despite the horror stories out there (like just about any other narrative around female pain), with a good healthcare practitioner, the insertion (or removal) process definitely doesn’t need to be something to fear.

Check out our full article all about how coils are inserted and what you can expect from the procedure.

How does the copper intrauterine device prevent pregnancy?

Right, so now we’ve been through alllll of that, our little T can get down to business. Once inserted the copper IUD will begin releasing veeery small amounts of copper ions into the uterus. 

The copper increases the volume and viscosity of cervical mucus (yep, that reaaaally sticky stuff) (1,2). This makes it very difficult for sperm to swim through or to survive through to the other end (2), which is the main way the copper IUD prevents pregnancy. 

Now, on the off chance that any of those pesky swimmers do make it through, sperm and copper have quite the toxic relationship. Sperm literally drop dead on contact with the copper (ouch) (1).

But the copper IUD doesn’t stop there, she's got one last trick up her Ts. Her last line of defence is called ‘foreign body reaction’, where the body creates localized inflammation (3). This is a normal process that happens whenever a foreign object enters the body (yep, okay apart from that one). This localized inflammation in the uterus makes it more difficult for an egg to implant and thus a pregnancy to occur (4).

Do you have a period on the copper intrauterine device?

Unlike some other forms of birth control (including the progestogen-only IUD) the copper IUD doesn’t suppress ovulation to prevent pregnancy—but we think we’ll let her off the hook (she’s doing a fair bit already). 

This means you’ll still have periods. Generally, bleeds are longer and heavier during the first few months of use, known as a ‘settling-in symptom’. But bleeding usually gets gradually lighter after this, returning to normal.

Copper intrauterine device benefits and ballbusters

Alrighty, so now we’ve taken a look at what it is, what it does and doesn’t do, let's dig into the pros and cons. 

PRO - The copper IUD is one of the longest-acting forms of birth control.
Once it’s in place, you only need to get it replaced every 5-12 years (depending on the brand). For ParaGard, you only need to get it replaced every 10 years—but if it doesn’t suit you, you can also get it taken out whenever you want.

PRO - the copper IUD is super low maintenance 

A huge benefit to LARCs is that you don’t need to remember to take them every day, or every time you have sex. Once inserted, you can forget alllll about that lil T and let it do its long job. 

PRO - the copper IUD doesn’t affect your natural hormone levels 

The copper IUD doesn’t contain any synthetic hormones or suppress ovulation which means your normal hormonal flux and menstrual cycle won’t be affected and you shouldn’t experience any nasty hormonal switch-ups side-effects. 

PRO - it can be inserted as emergency contraception

If inserted up to 5 days after unprotected sex the copper IUD is also a super effective form of emergency contraception.

CON - some people experience heavier periods.  

It’s really common to experience heavier periods and breakthrough bleeding during the first 6 months of use. Although bleeds normally return to as they were before after a few months, some people may experience continuing changes to their cycles (6).

CON - it needs to be inserted by a healthcare professional and can be painful

Both insertion and removal need to be done by a healthcare professional and can be painful for some people. This is usually the top reason people are put off from getting an IUD inserted. 

CON - you have a 6 fold increase in the risk of developing pelvic inflammatory disease (PID)

Although rare, PID can occur during the first 20 days after insertion if any microbes move in alongside your IUD(7). 

Who is the copper IUD safe for?

Being a LARC, the copper IUD is particularly useful for people who don’t have regular routines (like shift workers), or those of us who prefer a ‘pop it in once and forget about it’ vibe to our birth control.

It may not be safe for you if you’ve previously had a pelvic infection, frequently experience unexplained bleeding during sex or if you think your pregnant (it won’t terminate a pregnancy, just stop fertilization from happening).

And that’s a wrap

To sum it up, the copper IUD is one solid bit of birth control. It doesn’t have to feel scary (despite the insertion horror stories). Effective, long acting and low maintenance, the copper IUD is on to a winner. 

If you’re considering getting a copper IUD but need more information, get in touch—we’re all ears.

Written by

Annalisa Hayes (she/her)

Copywriter at Tuune, Annalisa has worked for various pioneering health-tech startups and healthcare companies with purpose-led missions. Driven by empowering people to take control of their health, she helps make the science behind hormones accessible for our community, so they can make clued-up choices about their healthcare.

Medically reviewed by

Dr. Alejandra Elder Ontiveros, MD, PHD (she/her)

Ale is a PhysicianScientist with a doctoral degree in Development Biology and Embryology and is currently a Postdoctoral Scholar at UCSF. Ale believes that the union of academia and business can lead to transformative discoveries for women’s health.

Scientifically researched by

Hannah Durrant (she/her)

Hannah is a Biomedical Content Writer at Tuune, with a BSc in Biomedical Sciences from University College London. She is passionate about bringing together the scientific community and the general public by disseminating modern science via digestible, engaging and thought-provoking content.