For a diagnosis of substance use disorder (drug addiction), you must first undergo a comprehensive substance abuse evaluation. This will include an assessment by a psychologist, a psychiatrist, or a credentialed drug and alcohol counselor. While urine, blood, and other lab tests may be used for the purposes of substance abuse assessment, these are not diagnostic tests. Substance use disorder is diagnosed as mild, moderate, or severe according to the number of symptoms present from DSM-5-TR. This is the most current edition of Diagnostic and Statistical Manual of Mental Disorders, published by APA (American Psychiatric Association).