Quick answer

Copper in the amounts found in typical supplements has not been linked with liver injury. Too much on a regular basis upsets the stomach, with nausea, cramps and vomiting, and over time can damage the liver. The adult upper limit is 10 mg a day from all sources, and high-dose zinc can cause the opposite problem: low copper.^1,2,3

Key facts

In a study of 61 adults, mild nausea was the most common reaction to copper dissolved in water, starting at 4 mg per liter.⁴
Seven people taking 10 mg a day as copper gluconate for 12 weeks reported no more stomach complaints than those on placebo.⁵
Copper toxicity is rare in healthy people whose bodies handle copper normally.⁶
Long-term zinc intakes of 50 mg a day or more can leave the body short of copper.³

Stomach upset

Getting too much copper on a regular basis can cause abdominal pain, cramps, nausea, diarrhea and vomiting.^2,6

When 60 healthy women drank water with added copper for two weeks at a time, nausea, abdominal pain or vomiting were reported by 17% at 3 mg per liter and 15% at 5 mg per liter, against 5% with no added copper and 2% at 1 mg per liter; blood copper and liver enzymes did not change.⁷

That study and a second one on nausea used copper sulfate dissolved in water, not capsules, so they show how copper on its own affects the stomach rather than what a supplement taken with a meal would do. In the second study, the same copper in an orange-flavored drink did not cause nausea until 8 mg per liter, and nobody vomited up to 12 mg per liter.^4,7

The liver

Long-term high intakes can damage the liver, and the upper limit is set from the amounts linked with liver damage.^2,6

LiverTox says the amounts of copper in typical supplements have not been linked with liver injury, while an accidental or intentional overdose can injure the liver and long-term excess can lead to copper overload and chronic liver injury.¹

People with Wilson's disease, a rare inherited condition in which the body cannot clear copper normally, are at high risk of copper toxicity and can develop liver and nerve damage.^2,6

The upper limit

The upper limit for copper is 10,000 mcg (10 mg) a day for adults, including during pregnancy and breastfeeding, and 8,000 mcg for teens 14 to 18, counting food, drinks and supplements. It is lower for children (1,000 mcg at ages 1 to 3, 3,000 mcg at 4 to 8 and 5,000 mcg at 9 to 13) and not set for infants. The limits do not apply to copper given under medical supervision.^2,6

European scientists took a different route in 2023: they asked at what intake copper starts to collect in the liver, and concluded that none is expected to build up at 5 mg a day. Both figures sit far above the 0.9 mg adults need.^6,8

Zinc and low copper

Low copper caused by too much zinc, including heavy use of zinc denture creams, can cause loss of coordination, numbness and weakness in the arms, legs and feet.^3,9

NIH says 50 mg of zinc a day or more, taken for weeks, can interfere with copper absorption. Other effects of a lack of copper include anemia, lightened patches of skin, high blood cholesterol, weak and brittle bones, loss of balance and coordination, and more infections.^2,3,6

Copper in drinking water

Copper toxicity has occurred when stagnant water in copper pipes and fixtures, or copper alloys in plumbing, leached copper into drinking water.⁶

The Environmental Protection Agency's recommended upper limit for copper in public water systems is 1.3 mg per liter.⁶

Medicines

Avoid the combination unless your doctor advises it

Penicillamine removes excess copper in Wilson's disease. Its label says multivitamins taken during treatment for Wilson's disease must be copper-free, that the diet should leave out supplements enriched with copper, and that mineral supplements should not be given because they may block the response to penicillamine.^10,11

On the medicine's label

NIH's copper fact sheets do not list medicine interactions, but the labels of the medicines that remove copper address minerals directly. Besides penicillamine's, the trientine label says to avoid mineral supplements such as iron, zinc, calcium or magnesium because they may reduce its absorption.^6,12

Who should ask first

People with Wilson's disease should not take extra copper²
People with liver disease
Anyone taking penicillamine or trientine
Anyone taking 50 mg of zinc a day or more³
Women who are pregnant or breastfeeding

Questions people ask

Is it safe to take copper supplements?

At amounts near what the body needs, copper from supplements has not been linked with liver injury, and the adult upper limit is 10 mg a day from all sources. People with Wilson's disease should not take extra copper, and people with liver disease should ask a doctor first.^1,2

Is copper safe during pregnancy?

Copper needs rise to 1,000 mcg a day in pregnancy and 1,300 mcg while breastfeeding. The upper limit is 10,000 mcg a day from age 19 and 8,000 mcg for younger mothers. Ask your doctor before adding a separate copper supplement.^2,6

Do chelated copper supplements have fewer side effects?

We found no study comparing side effects across forms. NIH notes that no studies have even compared how well the body absorbs copper from chelates, gluconate, sulfate or oxide.⁶

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Sources

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.