What Are Drugs?

Drugs are chemicals or plant products that affect the mind and body. They include legal substances such as alcohol and tobacco, along with over-the-counter medications, prescription medicines, and illegal substances.

When used appropriately, prescription and over-the-counter medications, also called therapeutic drugs, treat medical conditions and improve your health. However, problematic usage of drugs can lead to health risks, including addiction. Therefore, legal and illegal substance abuse can be separated into two general categories, depending on how a drug is obtained:

  • Drug use – this refers to using any illegal drug. People who use these substances ingest, inhale, smoke, or inject them into their bodies. Illegal drugs are often used for their mind-altering characteristics but may be taken for other purposes, such as weight loss or enhancing athletic performance.
  • Drug misuse – this refers to the use of medication in a way that is unhealthy or differs from what is recommended by a doctor. Drug misuse includes problematic usage of alcohol, tobacco, and over-the-counter medicines, as well as misuse of prescription drugs.

Drug use and misuse can lead to developing an addiction. Also called a substance use disorder, addiction is a chronic disease in which repeated drug use leads to changes in the brain. Addiction is complex, involving the brain, genetics, your environment, and life experiences. During an addiction, drugs or alcohol are continuously used regardless of their negative consequences.

If you’re concerned about drug use, misuse, or addiction in yourself or a loved one, don’t wait to have this conversation with your doctor or mental health professional. There are many effective treatment options for substance use disorders and addiction.

The Role of Drug Testing

Drug testing identifies the use or misuse of drugs. The most common use of drug testing is in the workplace as a pre-hiring requirement. Random or periodic drug testing may also be required after an employee is hired.

Who should get testing?

Employers may conduct drug testing when use is suspected based on symptoms observed in the workplace. You might be tested for drug use after an accident or incident on the job, such as a vehicle accident. If you have been absent from work for an extended period of time, your employer might request return-to-duty testing.

Drug screening may be used in many other contexts, including:

  • Legal or forensic testing – drug testing may be performed as part of an investigation or court case to provide evidence of a crime or in cases of child abuse or endangerment. Additionally, testing may be used to determine if you are drinking and driving or are publicly intoxicated.
  • Medical testing – you might be tested for drug use or misuse as part of a medical assessment. For example, if you are awaiting an organ transplant, you may receive drug testing and become ineligible if you receive a positive result. Doctors may also order a drug test if you are critically ill and experiencing a potential overdose.
  • Treatment adherence – drug testing may be ordered to monitor adherence to court-ordered treatment programs, as a term of probation, while participating in a substance abuse treatment program, or as part of an ongoing custody or parental rights case.
  • Monitoring for prescription drug misuse a doctor may order a drug test to monitor prescription drugs that have a potential for misuse, including opioids for pain.
  • Athletic testing – professional athletes often have to take a drug test to screen for drugs or other substances that are considered performance-enhancing.
  • Military testing – periodic or random drug tests may be required for members of the military.

More Drug Tests

Getting Tested for Drugs

Drug testing is performed in a wide variety of settings, including hospitals, laboratories, and other medical settings. Testing may also be conducted at both inpatient and outpatient drug treatment centers.

Costs of drug testing

The cost of a drug test will vary by location and test type. Find out in advance if you are responsible for covering the expense of pre-employment drug and alcohol screening or random testing.

Types of sample collection

The sample for a drug test depends on which substances the screening will identify. Most commonly, drug tests require a urine sample. Toxicology testing can also require a sample of blood, hair, or saliva.

Getting test results

Drug tests that are part of therapeutic drug monitoring are reported in the concentration the drug was found in the patient’s blood, while drug screening testing as part of toxicological examinations are typically reported as presumptive positive or presumptive negative. Those results indicate whether a drug was detected below or above the cut-off or threshold for a positive test result. There are several considerations to keep in mind when interpreting drug test results:

  • Confirmatory testing may be necessary – presumptive positive results on an initial drug screen usually need to be confirmed with additional, more specific, testing. Confirmatory testing uses a different type of drug test and improves the accuracy of drug testing by reducing the risk of false positive test results.
  • Drug tests may not evaluate intoxication – positive test results do not always mean you are currently intoxicated. Drug tests can detect drugs at a lower threshold than what would be required to produce physical effects. Additionally, some drug tests can detect the use of drugs for days or weeks after use, at which point the drug’s intoxicating effects have subsided.
  • Risk of false-positive results – medications and certain foods may produce false-positive results. Examples include poppy seed ingestion causing positive opioid test results and over-the-counter cold medicine resulting in positive PCP test results.
  • Risk of false-negative results – this occurs for several reasons, including improper sample collection or testing, subverting or falsifying a drug test, or not evaluating a drug in a test (e.g., amphetamine testing does not test all types of amphetamines). Commonly used ones, such as MDMA and methamphetamine, may not be found on all amphetamine drug tests.


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