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Drug Testing


Gerald F. O’Malley

, DO, Grand Strand Regional Medical Center;

Rika O’Malley

, MD, Grand Strand Medical Center

Reviewed/Revised Dec 2022

Drug testing involves checking for substance use in people who do not necessarily have any symptoms of intoxication or a substance-related disorder Substance-Related Disorders . It may be done systematically or randomly in

  • Certain groups of people, such as students, athletes, and prisoners

  • People who are applying for or who already hold certain types of jobs (such as pilots or commercial truck drivers)

  • People who have been involved in motor vehicle or boating accidents or accidents at work

  • People who have attempted suicide by unclear means

  • People in a court-ordered treatment program for drug abuse or with terms of probation or parole requiring abstinence—to monitor compliance

  • People in a substance abuse treatment program—to detect continuing substance abuse and thus better plan treatment

  • People required to undergo drug testing as part of custody or parental rights hearings

  • Members of the military

Typically, people have to give consent for drug testing except in certain circumstances, such as car or workplace accidents. Drug testing cannot determine how often a substance is used and thus cannot distinguish casual users from habitual users. Also, drug testing detects only some substances and misses many others. Substances most commonly targeted include

A sample of urine, blood, breath, saliva, sweat, or hair may be tested. Urine testing is most common because it is noninvasive, quick, and able to detect many drugs. It can detect drugs that were used within 1 to 4 days, sometimes longer, depending on the drug used. Blood testing is rarely done because it is invasive and can only detect drugs up to a few hours after use. Hair testing is not as widely available but can detect some drugs if they were used in the previous 100 days. Health care practitioners may directly observe the collection of the sample and seal it so that they can be sure the sample has not been tampered with.

Drug tests are not always accurate. The most commonly used urine tests give incomplete and sometimes incorrect results. Sometimes, the tests do not detect a drug the person is actually using (false-negative result). This can happen if the following occur:

  • The test is not designed or has limited sensitivity to detect a particular drug or drug component.

  • The urine is very dilute so that the amount of the drug in urine is less than the test can detect.

  • The person submits a sample from someone else or adds a substance to the urine to alter the sample.

On the other hand, the tests sometimes are positive when the person is not actually using drugs (false-positive result). For instance, poppy seeds can produce false-positive results for opioids (heroin is derived from poppy plants).

More Information

The following English-language resources may be useful. Please note that THE MANUAL is not responsible for the content of these resources.

  • National Institute on Drug Abuse (NIDA): Federal agency that supports scientific research into drug use and its consequences and supplies information about commonly used drugs, research priorities and progress, clinical resources, and grant and funding opportunities.

  • Substance Abuse and Mental Health Services Administration (SAMHSA): US Department of Health agency that leads public health efforts to improve behavioral health and provides resources, including treatment locators, toll-free helplines, practitioner training tools, statistics, and publications on a variety of substance-related topics.

Drugs Mentioned In This Article

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