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Toxicology Drug Testing

Medically reviewed by Leigh Ann Anderson, PharmD. Last updated on Dec 23, 2021.

Toxicology drug testing may be something you don't expect to happen to you, but it might. Workplace drug testing is increasingly common in the US, as is drug testing for athletes. What should you know?

In general, there are four types of toxicology testing:

Forensic Toxicology Analysis

Forensic toxicology testing, also known as postmortum toxicology testing, is conducted by a laboratory for medical and legal purposes, which may include death and criminal investigations. The results, which are often considered as evidence, may be subject to use in a court of law.

Forensic toxicology testing may occur after:

  • an accidental death, such as one involving a motor vehicle
  • a suspected homicide or suicide
  • suspected drug overdose or abuse.

Family members may also request an autopsy and toxicology report for a death that does not fall into one of the above categories.

Death investigations are conducted by law enforcement and health officials at the scene to gather any forensic evidence which may include prescription drugs, illicit substances, or over-the-counter medications, and any available information about the prescribers.

What happens during forensic toxicology testing?

Specimens for forensic toxicology analysis are collected during an autopsy that is completed by a medical examiner and pathologist. Standardized procedures are followed for gathering samples at the scene of a death to ensure reliable analysis.

  • All specimens, which may include blood, urine, hair, bone or organ tissue samples are gathered, maintained and disposed of with the utmost of care in a chain-of-custody fashion.
  • Blood may be taken from the heart and femoral leg vein, and is often preserved with sodium fluoride.
  • Tissue and fluid samples may be collected from the brain, liver, kidney, cerebrospinal fluid, vitreous humor (clear jelly from inside the eye), bile, and gastric (stomach) contents.
  • All laboratory procedures and analyses are done under scientifically sound and legally defensible standards, which includes initial and confirmatory testing.

Typical drugs and substances that may undergo toxicology screening for a forensic toxicology report include:

Testing samples are sent to a toxicology laboratory with board-certified forensic chemists. Testing procedures may include multiple tests run on various samples involving sophisticated equipment.

Tests may involves methods such as immunoassays, gas chromatography, or gas chromatography / mass spectrometry (GC/MS).

  • An immunoassay is a generalized screening test often used initially to detect broad-based drug groups like opiates, benzodiazepines or barbiturates.
  • Direct injection gas chromatography is used to detect alcohol.
  • The more specific GC/MS is used as a confirmatory test to identify individual drug substances and quantify the amount of the substance.

How long does it take get forensic toxicology test results?

Popular “crime scene investigation” television programs are able to complete toxicology reports in a very short (and unrealistic) time frame. However, in reality, while an autopsy is usually completed within a day or two after a death, the final results of the toxicology report may take four to six weeks or longer.

Many factors play into the length of time needed to gather forensic toxicology test results, including:

  • the need for confirmatory testing
  • the complexity of and the number of specific tests required
  • case workload and staffing at the testing laboratory.

Additionally, once toxicology results are available, there is an internal review process for quality control, and experts such as board-certified pathologists and toxicologists may be consulted. The final toxicology report may incorporate other information, such as field evidence at the scene of the crime, or the possibility of fatal drug interactions, to determine the cause of death. Finally, before the results of the toxicology test and cause of death can be made public, the family must be notified.1

Workplace Drug Testing

Workplace drug testing is often done when applying for employment, especially for positions that may involve federal transportation, airline industries, construction, and other workplaces where safety is of the utmost importance.

Drug testing is common for many U.S. employers, to lessen the impact from drug abuse in the workplace.2 The National Institutes of Drug Abuse (NIDA) reports that drug use costs the US economy more than $700 billion annually in increased health care costs, crime, and lost productivity.3

Pre-employment workplace drug testing usually requires that the applicant give a urine sample, but may also require saliva, sweat or hair samples prior to employment. In certain jobs, especially those that require a high level of safety, employees may be subject to random drug screening during employment, as well.

Random drug screening may be used in instances of workplace accidents, and if the employer has suspicion that the employee is abusing drugs. During the laboratory evaluation, strict chain-of-custody practices and standards are followed. Initial and confirmatory testing are also instituted.

Workplace drug testing is primarily limited to drugs with the potential for abuse, including some prescription drugs, and alcohol.

What happens during workplace drug testing?

  • An applicant is notified that pre-employment workplace drug testing will need to take place as part of the application process.
  • They may have to present to the laboratory within a specified time frame, for example within 24 hours, to lessen the chance that drugs in their system will be excreted and undetectable.
  • Applicants are directed to a laboratory to submit a sample for drug screening (usually urine).
  • Once at the facility, the applicant must submit a sample at the discretion of the laboratory personnel and in keeping with their standard policies.

Employers may use a standard five-panel test of “street drugs” that includes:

Some employers may elect a ten-panel drug test, that also includes various prescription drugs. Alcohol may also be screened for in the sample. Drugs that can be detected in hair-testing include alcohol, marijuana, cocaine, and amphetamines.

Many drugs stay in the system from 2 to 4 days, although chronic use of marijuana can stay in the system for weeks after the last use. Drugs with a long half-life, such as the benzodiazepine diazepam, may also stay in the system for a prolonged period of time. Drugs can be detected in hair samples up to 90-days, although urine samples are used for most workplace drug screening tests.

How long does it take get workplace drug testing results?

Results from workplace drug testing are fairly quick and can usually be received in a few days. Negative results are usually received within 24 hours, however, a positive screen will require further testing that may take a few days up to one week.

  • If the initial screen is negative, a medical review officer (MRO) will contact the employer with the results.
  • If a positive result occurs, a MRO will contact the applicant for further questioning. If contacted, it is important to notify the physician of any medications currently in use, including prescription, over-the-counter or herbal medications.
  • The applicant may also have the option of paying for a retesting of the sample they gave at a laboratory of their own choice.

Drug testing in states where marijuana use is legal

As of November 3, 2020, recreational marijuana use is now legal in at least 15 states and Washington, D.C., and is legal for personal medical use in over 3 dozen states and the District of Columbia (D.C.), Puerto Rico and Guam. Rules and laws surrounding the use of marijuana vary by state.

Some companies in states where marijuana is legal for either recreational or medical use are stopping drug tests for THC detection, or drug testing at all, in jobs that are not safety-sensitive.4

However, it is important that you know the requirements for drug testing in your workplace, even if you live in state where medical or recreational use is legal. Many employers still treat marijuana use as illegal. An employer can usually fire you for being impaired at work, and laws surrounding medical marijuana use and employment vary by state.

Medical Drug Testing

Clinical or hospital drug testing is conducted to assist in patient medical review, diagnosis and treatment.

  • Often this type of testing may occur when patients present to the emergency department with a suspected accidental overdose or poisoning, driving infraction with possible alcohol or drug involvement, or an accident involving injuries with suspicion of substance abuse.
  • Blood or urine testing is usually evaluated in these situations.
  • Blood samples from a venipuncture may be evaluated to determine elevated concentrations of prescription medications.

How is diagnostic drug testing performed?

Diagnostic drug testing is conducted in hospitals or clinic settings. For instance, a drug class, such as opiates, would be identified in a blood or urine sample, but the specific opiate, such as morphine might not be known.

While this might be sufficient for clinical use (for example to avoid a drug interaction or administer an antidote like naloxone (Narcan), more specific confirmatory tests would be required in cases involving drugs of abuse and to be used as evidence in a court of law. Confirmatory tests would be run if initial screening identified illegal drugs.

Routine clinical urine or blood chemistry testing (i.e., glucose, electrolytes, creatinine) is often completed in a hospital or clinic setting to assist with diagnosis and treatment, but is not considered drug toxicology testing.

How long does it take get clinical, diagnostic or hospital testing results?

Clinical laboratory testing is usually completed as quickly as possible to assist in diagnosis and treatment. The testing can often take place in the laboratory of the hospital where the patient presents for treatment. Time is important for a quick diagnosis, especially in overdose or poisoning cases. If drugs of abuse are detected, confirmatory testing may take additional time.

Athletic Drug Testing

What is athletic drug testing?

Athletic drug testing is done to detect banned substances or performance enhancing agents in competitive-level athletes. In the U.S, drug testing may occur in Olympic-level sports, National Collegiate Athletic Association sports (NCAA), and professional sports.

The U.S. Anti-Doping Agency (USADA) is the national anti-doping organization for the Olympic movement in the United States. Within the USADA, testing may occur in competition or out of competition and can occur at any time and at any location.5 View the World Anti-Doping Code Prohibited List here.

What happens during athletic drug testing?

Examples of drugs that may be tested for in athletes include:

As with other drug testing procedures in the U.S., a strict chain-of-command is followed according to defined standards. For a complete list of banned substances and procedures, consult the USADA website.6


See also


  1. Anon. Forensic Toxicology. Alabama Dept of Forensic Sciences. Accessed Nov. 28, 2018 at
  2. National Institute on Drug Abuse. Accessed Dec. 23, 2021 at
  3. National Institute of Drug Abuse. NIH. Frequently Asked Questions. What are the costs of drug use to society? Accessed Dec. 23, 2021 at
  4. The Coming Decline of the Employment Drug Test. Bloomberg News. Accessed December 15, 2020.
  5. U.S. Anti-Doping Agency (USADA), Sample Collection Process for Urine Testing. Accessed Dec. 23, 2021 at
  6. U.S. Anti-Doping Agency: Athlete Guide to Anti-Doping. Accessed Dec. 23, 2021 at

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.