Drug Testing:
Definition, Types, Uses & Comparison

Drug testing for employment is a screening process that uses biological samples (urine, hair, saliva, blood, or breath) to detect the presence or absence of legal or illegal drugs in job applicants or current employees. Employers use pre-employment drug tests to determine whether prospective employees abuse illegal drugs or prescription medications, making job offers contingent on passing these screenings.

The most commonly tested substances include amphetamines (including methamphetamines), cocaine, marijuana (THC), phencyclidine (PCP), and opioids (morphine, codeine, heroin). Employers can also request testing for additional substances like benzodiazepines, barbiturates, and alcohol, depending on their workplace drug testing policy and industry requirements.

Related terms: pre-employment drug screening, drug-free workplace policy, DOT drug testing, 5-panel drug test

Employers require drug testing for 7 main reasons:

• Pre-employment screening before hiring applicants to ensure candidates are suited for the position
• Random testing during employment to deter current employees from using drugs
• Post-accident testing to determine whether substance use caused workplace incidents
• Reasonable suspicion testing when employers observe signs and symptoms of drug or alcohol use
• Return-to-duty testing after employees test positive for illicit drugs or violate drug policies
• Periodic testing tied to annual physicals or work anniversaries in certain industries
• Federal compliance for safety-sensitive positions regulated by DOT, FAA, FMCSA, or other agencies

According to the 2020 National Survey on Drug Use and Health, more than 59 million Americans ages 12 and older admitted using illicit drugs within the past year. The National Institute on Drug Abuse reports that employees who abuse substances are likelier to miss work more often, be late to work, frequently change jobs, be involved in workplace accidents, and file more workers' compensation claims.

Pre-employment drug testing and routine screenings help protect workplace safety, boost productivity, reduce accidents and turnover, combat high absenteeism, and save costs. The National Safety Council reports that employees with substance use disorders miss an average of 24.6 days annually from work, excluding vacations and holidays.

Employment drug tests detect 5 primary substances in standard panels:

• Amphetamines, including methamphetamines (meth, crank, ecstasy, speed)
• Cocaine (crack, coke)
• Marijuana/THC (weed, cannabinoids, hashish)
• Phencyclidine (PCP, angel dust)
• Opiates (morphine, codeine, opium, heroin)

More comprehensive drug testing panels, such as the 10-panel test, can detect additional substances including barbiturates, benzodiazepines, methaqualone, methadone, and propoxyphene. Blood drug tests expand the detection range to include ethyl alcohol, fentanyl, oxycodone, buprenorphine, meperidine, tramadol, gabapentin, and carisoprodol.

The DOT panel tests specifically for amphetamines, cocaine, marijuana (THC), opioids, and phencyclidine (PCP), and is the only panel tested under DOT guidelines. This panel is consistent across regulated companies and drug testing laboratories.

Employers use 5 primary drug testing methods:

• Urine drug testing (UDT) - the most common test that detects drug residues remaining in the body after effects have worn off, with detection windows from 5 to 10 days
• Hair follicle drug testing - collects 100 strands of hair cut close to the scalp to detect drug use from up to 90 days before testing
• Saliva (oral fluid) testing - 100% observed collection that detects recent usage from 15 minutes to 1-3 days after drug use
• Blood drug testing - provides precise levels and types of drugs in the system at the time of collection, with detection windows of minutes to hours
• Breath alcohol testing - measures breath alcohol concentration (BrAC) to estimate blood alcohol content (BAC) for recent alcohol consumption

Urine tests are the most common type of pre-employment drug test used by employers in the U.S. and are the only method approved for federally-mandated testing. Urine testing is ideal for transportation and safety-sensitive roles where DOT compliance is critical.

Saliva testing is fast and convenient, identifying recent drug use and making it difficult for applicants or employees to cheat, dilute, or adulterate the test. Hair testing provides a longer detection window spanning up to 90 days and detects repeated drug use, though it does not detect current use or alcohol.

Detection windows vary by testing method and substance:

• Urine drug tests: 1 to 7 days for most substances, up to 30 days for marijuana in frequent users
• Saliva drug tests: 15 minutes to 48 hours after drug use, typically 1 to 3 days for most drugs
• Blood drug tests: Minutes to a few hours due to rapid metabolism and elimination
• Hair follicle tests: Up to 90 days, with scalp hair providing a 3-month window and body hair up to 12 months
• Breath alcohol tests: Current impairment only, measuring alcohol in the system at the time of testing

The timeframe for detecting drugs in your system depends on the type of drug, how much you used, how long you were using it before the test, and how your body metabolizes the substance. Your body metabolizes various drugs at different rates, so the detection window can be very specific and vary widely from substance to substance.

Urine tests show whether an employee has recently used drugs, not current impairment. Hair testing only detects past drug use and will not detect current use or alcohol. Saliva testing identifies recent usage and can detect as recently as 15 minutes after drug use.

The employment drug testing process includes 9 standard steps:

1. Employer extends a conditional job offer contingent on passing the drug screen
2. Applicant receives notice of the drug testing requirement and provides written consent
3. Applicant is given instructions for the testing location and must report within 24 hours (or as specified)
4. At the collection site, the applicant provides a government-issued ID and empties pockets
5. The collector ensures the restroom has no access to water sources or adulterants, and toilet water contains bluing agent
6. Applicant provides a biological sample (urine, saliva, hair, or blood) under observation protocols
7. The sample undergoes an initial screen to determine the absence or presence of detectable drugs
8. If positive, a confirmation screen is performed with review by a medical review officer (MRO)
9. Results are provided to the employer and applicant within 1 to 3 days

For urine samples, the applicant will be asked to empty pockets, remove outer garments, leave bags behind, and wash hands before entering a restroom where water sources are disabled and the toilet contains bluing agent. The collector will not note prescription drugs on the chain of custody form.

The chain of custody tracks the sample from collection through analysis and disposal. Most pre-employment drug screenings take a few minutes at the collection site, and results are typically available within 1 to 3 business days, depending on the method used.

A positive result indicates that a drug was detected at or above the reference range for that test. This means the person had a detectable amount of a substance present during a certain window of time. A positive result does not necessarily mean the person is currently intoxicated or experiencing the effects of the substance, nor does it automatically indicate a substance use disorder.

Positive results on an initial drug test usually need confirmation with additional testing using a different method. Confirmatory testing improves accuracy by reducing the risk of false-positive results, which can occur when someone tests positive for a drug even though they never used it. Medications and certain foods may produce false-positive results. For example, consuming poppy seeds can cause a positive opioid test result, and taking over-the-counter cold medicine can cause a positive result for PCP.

A negative result means that either the drugs tested were not found in the sample or a very small amount of drugs was found but not enough to count as a positive test result. A negative result does not rule out recent substance use or a substance use disorder.

False-negative results can happen when a person tests negative for drugs despite drug use due to improper sample collection, attempted falsification (using someone else's urine), the specific drug not being evaluated in the test panel, or drug levels below the detection threshold.

Federal employment drug testing laws include the Drug-Free Workplace Act of 1988, which mandates drug testing policies for employers that receive federal contracts worth $100,000 or more or any federal grants. Under this law, federal contractors and grant recipients must create and distribute a formal drug-free workplace statement, establish a drug awareness education program, and take action against employees who violate the policy.

The Omnibus Transportation Employee Testing Act of 1991 requires drug testing programs for employers in the transportation industry regulated by FMCSA, FAA, FTA, FRA, U.S. Coast Guard, PHMSA, or NHTSA. Regulated employers must comply with the regulations and rules established by their regulating agency for drug-testing programs.

The Americans with Disabilities Act (ADA) prohibits workplace discrimination based on disability and applies to employers with 15 or more employees. The ADA does not prohibit drug-free workplace policies but does prohibit employers from refusing to hire or promote someone solely based on their past history of substance abuse or enrollment in a drug rehabilitation program. However, the ADA does not prohibit employers from refusing to hire applicants or terminating employees based on current illicit substance use.

Title VII of the Civil Rights Act of 1964 prohibits employers from discriminating against applicants or employees based on race, national origin, color, or religion. This law requires employers with 15 or more employees to ensure their drug testing policies do not single out groups for testing based on protected characteristics.

State laws on employment drug tests vary widely. Most private employers do not have a federal drug-free workplace policy requirement, but there are exceptions for federal contractors and companies operating in specific industries. Employers should consult legal counsel before implementing workplace drug testing policies to ensure compliance with relevant federal, state, and local laws.

If an applicant fails a pre-employment drug test, the employer will withdraw the conditional offer of employment. The applicant will not be eligible for the position, as the offer was contingent on passing the pre-employment drug test.

If a current employee fails a drug test, the consequences depend on the employer's written drug testing policy and whether the employer is subject to federal regulations. In federally regulated industries, there is no flexibility and the rules are not open for interpretation. For most private employers, the response depends on their company policy.

Many private employers will not terminate an employee for a one-time positive drug test. They may request that the employee attend rehabilitation and allow them to retain their position under certain conditions. The employee may be denied a promotion or face other consequences. Employers must consistently follow their written drug testing policy to avoid accusations of discrimination.

When a positive result is confirmed, a medical review officer (MRO) will review the chain of custody and test results. The MRO may contact the individual to ask about prescription medications that might explain the positive test. Within 72 hours of notification, the individual has the right to request a retest of the original sample or split specimen at their own expense.

According to the Drug-Free Workplace Act, employers must take action against employees who violate the drug-free workplace policy by terminating them or requiring them to complete a drug rehabilitation program before returning to work.

Employers can still test for marijuana and take action against employees who test positive, even in states where marijuana is legal for recreational or medical use. Many employers want to maintain drug-free workplaces, and marijuana remains illegal under federal law.

If an employee tests positive for a legal drug prescribed by their provider, employers cannot punish them unless the drug is affecting their ability to perform their job. However, state laws vary on marijuana testing, and some recent appellate decisions have limited employer actions. For example, a recent Pennsylvania decision held that employers cannot discipline medical marijuana users for positive marijuana tests.

Employers should review their state's laws before implementing or enforcing marijuana testing policies. Despite state-level legalization, employers in safety-sensitive industries or those subject to federal regulations (such as DOT) must continue to test for marijuana and take action on positive results to maintain compliance.

Drug testing for employment is often compared to 3 related workplace screening methods:

Drug Testing vs. Background Check

Drug Testing vs. Medical Examination

Drug Testing vs. Alcohol Testing