The aim of the study was to evaluate the effects of a diet containing different levels of Cu in two differentchemical forms (carbonate and nanoparticles) on metabolic, immune and antioxidant status in a rat model. Fiveexperimental treatments (8 rats in each) were used to test different dosages of Cu added to the diet (standard−6.5 mg/kg, half the standard dosage−3.25 mg/kg, and no added Cu as a negative control) and two sources ofadded copper (standard−CuCO3and copper nanoparticles−CuNPs). Blood and urine samples were collectedfrom all the animals after four weeks of treatment. Metabolic and immune parameters were determined in bloodand urine samples. The study has shown that a dietary Cu deficiency (negative control) decreases rat’s plasmalevels of Cu, Fe, CREAT, BIL and IL-6, whereas reducing the level of Cu from the recommended 6.5 mg/kg to3.25 mg/kg decreases only the plasma concentration of TG, IgE and IL-6. Replacing CuCO3with CuNPs in ratdiets affects their metabolism, as indicated by decreased Ca, CREAT, BIL, ALB and IL-6 plasma levels. To sum up,CuNP added to a diet of rats have a more beneficial effect on metabolic indices (indicative of kidney and liverfunction) and inhibit inflammatory processes more effectively than CuCO3.