A substance can be legal but may be banned in certain circumstances. For instance, an insurance company may test an insurance applicant for nicotine to verify the person's assertion that he or she is not currently using tobacco. In the case of prescription medications, the high addictive potential for certain medications makes drug testing important. In the case of some athletes, many of the prohibited substances are legal but have the potential to affect the athlete's performance. Athletes must exercise caution in their choices of medications as they are ultimately responsible for any substances detected in their bodies.