Copper
Copper is a cofactor for enzymes that move electrons and iron: cytochrome c oxidase in mitochondria, superoxide dismutase, and ceruloplasmin, which prepares iron for transport. Dietary deficiency is rare. When deficiency does occur, the most common cause is too much zinc, and it can masquerade as iron deficiency anemia, a low white count, or a spinal cord disease.
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What It Does
Copper enters intestinal cells through the CTR1 transporter and leaves them through ATP7A. In the liver, ATP7B loads copper onto ceruloplasmin and sends the excess into bile; mutations in ATP7B cause Wilson disease, in which copper accumulates in the liver and brain. Ceruloplasmin oxidizes iron so it can bind transferrin, which is why copper deficiency causes an anemia that iron does not fix. Lysyl oxidase uses copper to cross-link collagen and elastin. Deficiency also produces neutropenia and a myelopathy that closely resembles B12 deficiency, with unsteady gait and numb feet (Kumar 2006).
The zinc-copper seesaw runs through one protein. Zinc induces metallothionein in intestinal cells, and metallothionein binds copper more tightly than zinc. The copper is trapped and lost when those cells shed a few days later. That is exactly how zinc treats Wilson disease (Schilsky 2023). In anyone else, months of zinc above about 40-50 mg a day can produce the same depletion (Willis 2005). Large amounts of zinc-containing denture cream have caused it too (Hedera 2009), as has bariatric surgery.
Most people should not take copper on its own. A mixed diet supplies about 1-1.5 mg a day, the body has no efficient way to dispose of excess except through bile, and chronic overload damages the liver. Copper supplements make sense with long-term zinc, after bariatric surgery, and for documented deficiency under medical care. Use the Zinc/Copper Ratio calculator to check your combined intake from all products.
Forms and Bioavailability
Absorption ratings are broad tiers. Head-to-head human trials rarely support a finer ranking among well-absorbed forms.
| Form | Elemental % | Absorption | Typical dose | Cost | Labels |
|---|---|---|---|---|---|
| Copper Gluconate | 14% | HighSoluble salt absorbed through the CTR1 transporter in the small intestine; the fraction absorbed falls as intake rises. | 1-2 mg elemental copper daily | Low | 20 |
| Copper Bisglycinatecopper glycinate, chelated copper | 30% | HighCopper bound to glycine. Absorbed well, with few human comparisons against simple salts. | 1-2 mg elemental copper daily | Moderate | 101 |
| Copper Sulfatecupric sulfate | 25.5% | HighSoluble and well absorbed; more GI irritation on an empty stomach. | 1-2 mg elemental copper daily | Low | 9 |
| Cupric Oxidecopper oxide | 79.9% | LowNearly insoluble and poorly absorbed; animal data led to the recommendation that it not be used as a copper source. | Avoid as a copper source | Low | 3 |
Labels column: number of labels named as copper products that list this form. A product can list more than one form, and some labels do not state a form at all.
Gluconate, bisglycinate, and sulfate are all soluble and well absorbed; the differences among them are small. Cupric oxide is nearly insoluble, and a review of the animal data concluded that it should not be used as a copper source for animals or humans (Baker 1999). It still appears in inexpensive multivitamins because it packs the most copper into the least space. Serum copper and ceruloplasmin are the usual tests; ceruloplasmin rises with inflammation, pregnancy, and estrogen, which can hide a deficit.
Typical Dosing
| Group | RDA |
|---|---|
| Adults 19+ | 900 mcg |
| Pregnancy | 1,000 mcg |
| Lactation | 1,300 mcg |
| Upper limit (UL) | 10,000 mcg (10 mg) per day from all sources |
Most people meet the RDA from food. When zinc is taken long term above about 25 mg a day, 1-2 mg of copper is a common pairing. Diagnosed copper deficiency is treated under medical supervision.
Food sources: beef liver, oysters, crab, cashews, sunflower seeds, dark chocolate, lentils, mushrooms.
What to Look For
Check your multivitamin first; many already contain 0.5-2 mg of copper, often enough to offset moderate zinc. If you take zinc above about 25 mg a day for more than a few weeks, add 1-2 mg of copper or choose a zinc product that includes it. Take copper with food to avoid nausea.
Do not take copper with Wilson disease, and talk to a clinician before taking it with liver disease. If you have taken high-dose zinc for months and develop anemia, a low white count, or numbness and unsteadiness, ask for serum copper and ceruloplasmin.
Red flags: copper as the cupric oxide form, standalone copper at 2-5 mg taken without a reason, and copper bracelets for arthritis. Green flags: a soluble form named, elemental copper in mcg or mg, and a zinc-to-copper pairing that makes sense.
Copper Gluconate
Inexpensive and well absorbed. The simplest way to add 1-2 mg alongside zinc.
What to look for: Copper (as gluconate) 1-2 mg per tablet, taken with food.
Find on iHerb Affiliate linkCopper Bisglycinate
Common in zinc and multimineral combinations. No proven advantage over gluconate.
What to look for: Elemental copper stated, ideally inside the zinc product you already take.
Find on iHerb Affiliate linkCopper Sulfate
Standard in multivitamins and in medical treatment of deficiency. More stomach upset when taken fasting.
What to look for: Take with a meal; check the total across all products.
Find on iHerb Affiliate linkProducts on Titrate
13,796 of the 214,745 labels in the NIH Dietary Supplement Label Database list copper as an active ingredient (6,626 on market). 193 are sold as copper products by name.
Top on-market labels, ranked by label completeness and simplicity:
Copper does not have its own search category yet. Each product above links to its full label in the NIH database.
Related Tools
References
NIH Office of Dietary Supplements. Copper: Fact Sheet for Health Professionals.
Baker DH. Cupric oxide should not be used as a copper supplement for either animals or humans. J Nutr. 1999;129(12):2278-2279.
Willis MS, Monaghan SA, Miller ML, et al. Zinc-induced copper deficiency: a report of three cases initially recognized on bone marrow examination. Am J Clin Pathol. 2005;123(1):125-131.
Kumar N. Copper deficiency myelopathy (human swayback). Mayo Clin Proc. 2006;81(10):1371-1384.
Hedera P, Peltier A, Fink JK, Wilcock S, London Z, Brewer GJ. Myelopolyneuropathy and pancytopenia due to copper deficiency and high zinc levels of unknown origin II. The denture cream is a primary source of excessive zinc. Neurotoxicology. 2009;30(6):996-999.
Schilsky ML, Roberts EA, Bronstein JM, et al. A multidisciplinary approach to the diagnosis and management of Wilson disease: executive summary of the 2022 Practice Guidance on Wilson disease from the American Association for the Study of Liver Diseases. Hepatology. 2023;77(4):1428-1455.
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