An increasing number of athletes are deciding to take dietary supplements as an effort to improve the general condition of the body and / or gain an advantage over their competition. Dietary supplements are not medicines, they do not cure diseases, but they can prevent them and relieve some symptoms. They can also enhance immunity and improve the general condition of the body, but only if used as recommended by experts. The aim of this paper is to provide an overview of the latest scientific findings on the effectiveness of commonly used dietary supplements for athletes, with particular emphasis on their ergogenic impact, that is, the effect on increasing efficiency, strength and endurance. The dietary supplements studied are creatine, branched chain amino acids, glutamine, l-carnitine, collagen, B-group vitamins, magnesium, zinc, and calcium and vitamin D. Rehydration in athletes is best achieved with isotonic drinks consisting of 20-30 mEq / L sodium, 2-5 mEq / L potassium and 8% carbohydrates. Of the above dietary supplements, ergogenic activity has been proved only with creatine supplementation in the amount of 0.3g / kg of body mass per day in fast and explosive disciplines, while for other sports disciplines the same effect has not been proven. With sufficient energy intake and a balanced diet, the athlete receives sufficient amounts of macronutrients and micronutrients, so supplementation is not required. It is only recommended in certain conditions because of the inability to achieve a balanced diet or clinically proven nutritional deficiency.