According to a 2013 survey by Planned Parenthood, IUDs are the most popular form of contraception among women’s health providers. And that’s not so surprising: IUDs are 99 percent effective and can last anywhere from 3 to 12 years, depending on the type. Plus, there’s no need to remember to take a daily pill.

It’s natural to be a little skeptical when reviewing the IUD’s impressive resume. Maybe you’ve raised an eyebrow at the gynecologist’s office or simply wondered to yourself, “Are these tiny, T-shaped devices too good to be true?”

If you’ve researched IUDs, you may have stumbled across the concern that the ParaGard, a non-hormonal IUD that’s partially made from copper, can cause copper toxicity in the body. To get to the bottom of this ParaGard puzzle, we asked the experts: should women be concerned about getting copper toxicity from this type of IUD?

Catch me up. What’s the ParaGard?
The ParaGard works to prevent pregnancy while inserted in uterus, and is the only non-hormonal IUD approved by the FDA. While other IUDs, like the Mirena and Skyla, emit progesterone to prevent pregnancy, the ParaGard relies on copper. “The ParaGard has a T-shaped plastic frame with copper wrapped around the stem,” says Dr. Sara Zarè, a Naturopathic Doctor at San Francisco’s Radiant Health who has experience in family planning and IUD insertion. “This continuously releases copper into the lining of the uterus. The copper produces an inflammatory reaction that’s toxic to sperm, which is how it works to prevent pregnancy. In fact, this reaction can prevent pregnancy for up to 10 years after insertion.”

Dr. Shaun Samples, an OBGYN at WOMEN Obstetrics & Gynecology in Nashville, Tennessee, offers this helpful analogy: “The copper in the ParaGard prevents pregnancy by disabling sperm from swimming. Sperm have to run an obstacle course to fertilize the egg and their interaction with copper makes their performance suffer.”

What’s copper toxicity?

First, it’s important to note that copper is important for nerve function and bone growth. The Mayo Clinic recommends adolescents and adult women get 1.5 to 3 mg of copper a day through food or supplementation. Lentils, sunflower seeds, beef liver, dark chocolate, and almonds are all great copper-rich foods.

But Dr. Zarè warns that, like many things in life, going overboard isn’t a good idea. “Copper is an essential trace element critical for normal human metabolism,” she says. “Copper deficiency can occur with inadequate copper intake, but excess copper intake may cause toxicity to humans.” Excess copper can result in symptoms like fatigue, headaches and migraines, mood swings, paranoia, a racing heart, aching muscles, and problems with concentration or memory, according to the website Nutritional Balancing, which comes recommended by Dr. Zarè.

The final say
It’s normal to wonder if the ParaGard, which can emit copper into the uterus for up to 10 years, could also cause copper toxicity. But according to clinical studies and both doctors we consulted, there’s little need to worry. “Studies have shown that the level of copper in your blood does not increase with the ParaGard,” says Dr. Samples. “Using the medical definition of ‘copper toxicity,’ there have been no cases related to the copper IUD in literature that we can find. The amount of copper in an IUD, even if swallowed, would not be sufficient to cause toxicity.”

Dr. Zarè backs up this statement, and points to several clinical studies that offer further evidence, like this one published in August 2017.

Remember, you’re the only expert of you
That being said, Dr. Samples adds that there are women whose bodies don’t react well to the copper IUD, like those with copper allergies or Wilson’s Disease, as the ParaGard may cause too much discomfort or simply not feel right inside of your body. “When you consider that each human being, except for identical twins, has a unique biochemical structure, we can’t be sure exactly how any medication or device will be tolerated by a particular person,” she says. “We may be experts in medicine, but you are the only expert in you. The beauty of a reversible contraceptive like the ParaGard is that you can stop using it if you do not feel like yourself.”

English Taylor is a San Francisco-based women’s health and wellness writer and birth doula. Her work has been featured in The Atlantic, Healthline, Refinery29, NYLON, and Modern Fertility. Follow English and her work at https://medium.com/@englishtaylor or on Instagram at @englishtaylor.