Tolerance is a symptom of substance use disorder. It refers to a stage of the disease entered by the alcoholic or addict after a period of alcohol or drug use, in which it will take an increasingly greater amount of the substance to have the same effect on the addict that it did in the beginning of his substance use. Tolerance also indicates something about the condition of the individual’s body: as his tolerance to the drug or alcohol increases, he will need more of it to reach the state of consciousness that he desires.