Workplace drug testing is widely used not only in the USA but also in many developed countries to deter employees from drug abuse. People try to beat drug tests by substituting urine with synthetic urine or by adding adulterants to the urine after collection. It is relatively difficult to detect synthetic urine, but there are a few methods that may identify synthetic urine. However, if not detected prior to the analytic phase, a person will pass drug testing. Moreover, people also add household chemicals in vitro after collection in order to beat a drug test. Although most adulterants can be detected in pre-analytical step by specimen integrity tests (pH, specific gravity, temperature and creatinine), adding Visine eye drop to urine after collection may not be detected by such test. In addition, many adulterants which are strong oxidizing agent became available to beat drug tests through the Internet or calling specific telephone number. Although such adulterants are added in vitro to urine after collection, specimen integrity testing cannot identify such adulterants. However, specific urine dipsticks, automated assays and specialized liquid chromatography combined with tandem mass spectrometry are available to identify such adulterants prior to analytical phase. Identifying such adulterants prior to analysis is essential because some adulterants are capable of invalidating drug testing not only during the immunoassay screening stage but also during confirmation.