Most people consume less than the recommended amount of this mineral. Some doctors recommend supplementing the average diet with 1–3 mg of copper per day. While the necessity of supplementing a normal diet with copper has not been proven, most people who take zinc supplements, including the zinc found in multivitamin-mineral supplements, should probably take additional copper.

Cupric oxide (CuO) is a form of copper frequently used in vitamin-mineral supplements sold over-the-counter. However, animal studies have shown conclusively this form of copper is poorly absorbed from the gut; it should therefore not be used in supplements.^1,2,3,4 Several other forms of copper (including copper sulfate, cupric acetate, and alkaline copper carbonate) are better absorbed, and are therefore preferable to cupric oxide.⁵