Drug and alcohol testing may help the emergency physician (EP) determine whether behavior is likely caused by acute intoxication versus a medical condition versus an acute exacerbation of psychiatric illness as well as guide the timing of reassessments and a reliable mental status examination. The current American College of Emergency Physicians' (ACEP) clinical policy on the evaluation of psychiatric patients presenting to the emergency department cites numerous literature sources concluding that laboratory testing is often unnecessary and is often inaccurate. In addition, positive urine drug test results often do not affect outcome or patient disposition. Each patient's level of cognition should be assessed on an individual basis. When a patient is hemodynamically stable and can provide a history and cooperate with a physical exam and all are consistent with their presentation, routine drug and alcohol testing can be avoided.