The basic functions of bioelements in biological systems is widely known. Depletion of bioelements and excess of toxic elements lead to impairment of metabolism in the living organism. The existence of magnesium deficiencies in the adult and pediatric populations may cause increased accumulation of toxic metals including lead and cadmium. Prevention of adverse effects of toxic metals may include supplementation with some bioelements and vitamins. The aim of this study was to evaluate the influence of magnesium supplementation on concentrations of chosen bioelements and toxic metals in hair in the adult human population. The research was performed on 124 individuals (53 males and 71 females aged 19-72 years), inhabitants of the city of Szczecin. The concentrations of magnesium, zinc, copper, lead and cadmium were studied in hair. Measurements were performed using the inversion volt-amperometry method with application of an EDD-Tribo PC ETP volt-amperometer. Finally, the supplementation study enrolled 65 individuals with an increased concentration of lead. The studied individuals were divided into two groups: one treated group that enrolled 50 patients who were supplemented with magnesium and the control group that enrolled 15 persons receiving placebo. Finally, supplementation was completed by 32 individuals from the treated group and 10 individuals from the control group. Supplementation was performed using Slow-Mag-B6 preparation at the total daily dose of five tablets divided into 2-3 doses. One tablet contains 535 mg of magnesium chloride i.e. 64 mg of magnesium ions (5.26 mEgMg2) and 5 mg of vitamin B6. Supplementation was performed for a period of 3 months. The remaining individuals did not complete the supplementation due to various reasons; however, none of them resulted from the poor tolerance of the preparation or its adverse events. The results achieved underwent statistical analysis. The results of the study revealed a positive influence of supplementation on concentrations of magnesium and copper in the human body. Supplementation with magnesium caused a statistically significant decrease in concentrations of lead and cadmium. The above mentioned results indicate a positive influence of magnesium supplementation on the decrease of lead and cadmium hair content in the individuals studied.