Fentanyl

Drug testing is the process of detecting one or more prohibited and/or approved substances in urine or, to a lesser extent, in blood, saliva, hair, and sweat. Typically, an initial test is followed by a second test that identifies and/or confirms the presence of the drug or narcotic.

For most drugs of abuse, the initial test is compared to a predetermined range. Values below this reference range are considered negative, while values above it indicate a positive test result.