Doping control is a very important issue. In order to prevent that athletes use banned substances and keep the fairness of the contest, not only the Olympic Games but also regional sport tournament will all carry out doping control. In some cases, athletes denied the use of doping. The fact is that athletes might take some products contained prohibited substances, especially products as unknown substances, nutritional supplements, or weight loss medicine. It might due to these products not clearly declared on the labels, cross-contaminated, faked with prohibited substances, or metabolized to prohibited substances. Therefore, athletes should be more careful for taking these products.