Drug testing, such as through urinalysis, provides an objective or impartial measure of drug use. This objective measure stands in contrast to self-report measures of drug use, in which individuals are asked to describe subjectively their alcohol- or drug-using behaviors. Research has consistently documented that objective measures of drug use are more reliable indicators of actual drug use than self-report measures. Simply put, individuals are naturally inclined to hide embarrassing behaviors when given the chance to do so. Drug tests greatly reduce the likelihood of hiding recent drug-using behaviors.

Drug tests, like urinalysis, detect the presence of most drugs within 72 hours of use. After this window has passed, most drugs become undetectable. The exception is marijuana, which can be detected in urine for up to 30 days. Most drug tests cannot, however, identify historical use or drug dependence. Drug tests can only stipulate whether an individual has used a particular drug recently.