Drug Testing FAQs
Medically reviewed on May 1, 2017 by L. Anderson, PharmD.
On this page:
- Drug testing facts
- What types of laboratory tests are used for drug testing?
- What happens during drug testing in the workplace?
- How long can drugs be detected in the body with a drug test?
- How long does it take get workplace drug testing results?
- What are the chances that a workplace drug test will result in a false positive or a false negative?
Drug testing is the evaluation of a urine, blood or other type of biological sample to determine if the subject has been using the drug or drugs in question. There are many circumstances that may lead to drug testing:
- Pre-employment drug screening test or random, work-related drug testing to identify on-the-job drug abuse.
- College or professional athletic drug testing.
- Post-accident drug testing - a vehicular or on-the-job accident which may have involved human error and resulted in casualties or property damage.
- Safety-related drug testing - if an employee's job could lead to safety issues if judgement or physical ability were impaired.
Drug testing is often done when applying for employment, especially for positions that may involve federal transportation, airline industries, railways, hospitals, and other workplaces where public safety is of the utmost importance. However, workplace drug testing is now common in general for many U.S. employers to lessen the impact from drug abuse, safety concerns, and low productivity in the workplace.
Prescription drug abuse is a serious problem in the U.S. The Surgeon General, as reported by NIDA, states that alcohol and drug abuse, including tobacco, costs the economy over $740 billion per year. Costs are related to crime, lost work productivity and health care. Over 9.5 million urine drug tests were positive in the U.S. workforce in 2015. The rates increased to 4% of workers tested in 2015 versus 3.9% the year before, per Quest Diagnostics.
A pre-employment drug test is primarily limited to drugs with the potential for abuse, including some prescription drugs, and alcohol. In addition, sports drug testing may be required for college-level, professional and Olympic athletes. Illegal recreational drugs, performance-enhancing drugs such as
- anabolic steroids
- recombinant human growth factors
- other drugs, such as those listed on the World Anti-Doping Code Prohibited List
may also be required in sports testing.
Pre-employment workplace drug testing usually requires the applicant to give a urine sample, but may also infrequently require blood, saliva, sweat, or hair.
In certain jobs, especially those that require a high level of safety, employees may be subject to random drug testing, 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. Random drug testing may occur without cause for suspicion depending upon company policy.
Some U.S. companies may offer employee-assistance programs to support substance-abuse treatment, but many employers are not tolerant of this issue and it may result in termination from employment.
It is important to be sure that the drug testing occurs at a reputable and certified laboratory. Any credible drug screening program will involve a two-step process. Initial (immunoassay) and confirmatory (gas chromatography-mass spectrometry) - GC-MS test - are the methods most commonly utilized to test for drugs. Using a combination of both tests allows a high level of sensitivity and specificity, meaning there is an extremely low chance for false positives or false negatives.
The immunoassay is performed first and is often used as a screening method. If the immunoassay is negative, no further action is required, and the results are reported as negative. If the sample is positive, an additional confirmatory GC-MS analysis is performed on a separate portion the biological sample, per Lab Tests Online. The more specific GC/MS is used as a confirmatory test to identify individual drug substances or metabolites and quantify the amount of the substance. Confirmatory tests, such as GC-MS should be utilized prior to reporting positive drug test results.
Urine drug testing
Urine is the most common sample type used for drug testing by employers. A urinalysis will show the presence of a drug in the system after the drug effects have worn off; however, the length of time varies by drug. Typical urine drug tests for employment purposes may screen for amphetamines or methamphetamines, cocaine, marijuana, opiates like oxycodone or heroin, nicotine, and alcohol, as reported by The Balance.
Saliva drug testing
Saliva (oral) testing, also called a mouth swab test, may be used if an employer or other tester is interested in knowing about recent drug use, but is not ideal to survey long term use of drugs. Most saliva drug tests can detect most usage within a few hours up to 3 days. Saliva is an easy lab test to gather samples, is less susceptible to adulteration, and can be tested for alcohol, marijuana, cocaine, amphetamines, and methamphetamines.
Blood drug testing
A blood drug test may be used to determine amounts of drug in an employees system at that very moment. A variety of drugs can be tested for in blood: amphetamines, cocaine, marijuana, methamphetamines, opiates, nicotine, and alcohol. Blood testing is invasive but there is little chance for adulteration. Blood testing may be performed in the emergency room for toxicology testing, as well.
Hair drug testing
Hair testing may be used to determine drug use over the longer term, usually over a 90-day period of time. Hair can be tested for cocaine, marijuana, opiates, methamphetamine, phencyclidine, and alcohol.
An applicant is notified that pre-employment drug testing will need to take place as part of the application process, and 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 specific laboratory to submit a sample for drug screening (usually for urine test results).
Once at the facility, the applicant must submit a sample at the discretion of the laboratory personnel and in keeping with their standard policies. Hair, sweat, saliva or blood drug test samples may also be used in pre-employment drug screen, although this is not common practice, per Lab Tests Online.
During the laboratory evaluation, strict chain-of-custody practices and standards are followed to prevent adulteration of the sample. This legal procedure requires documentation of each person who handles the specimen through the entire phase of testing. Certain laboratory procedures may require direct visual observation while the specimen is being voided.
5 Panel Drug Test
Employers may use a standard five-panel test of "street drugs" that includes:
- marijuana (THC)
- opiates (e.g., codeine, morphine, heroin)
- amphetamines (e.g., methamphetamine).
10 Panel Drug Test
Some employers may elect a nine- or ten-panel drug test that also includes various prescription drugs, such as:
- oxycodone, methadone or other narcotic prescription drugs
- MDMA (Ecstacy)
Alcohol drug testing may also occur. Other more recent designer drugs of abuse may be included. Which drug test is used is dependent upon the private employer, federal requirements, or other workplace guidelines that may be in place, per US Healthworks and MobileHealth.
Who are the companies that drug test?
- Laboratory Corp of America Holdings
- Quest Diagnostics Inc.
- National Toxicology Labs, Inc.
- Phamatech, Inc.
Other companies that are used for federal workplace dug testing can be found by state at SAMHSA.gov.
Many variables may affect the amount of time that a drug remains detectable in the urine or other biological samples, including:
- a drug's half-life
- subject's state of hydration and fluid balance
- frequency of drug use
- route of administration
- cut-off concentration used by the testing lab to detect the drug.
General guidelines are available for detection times. Many drugs stay in the system from 2 to 4 days, although chronic use of marijuana can stay in the system for 3 to 4 weeks or even longer after the last use.
Drugs with a long half-life, such as diazepam, may also stay in the system for a prolonged period of time. Drugs can be detected in hair samples up to six months, although urine drug screen tests are used for most workplace drug screens. Examples of drugs that can be detected in hair-testing include alcohol, marijuana, cocaine, and amphetamines.
Drug Test Chart and Drug Detection Times*
|Drug||Class||Street Name||Prescription Brand Name Examples||Detection Time in Urine|
|Amphetamine||Stimulant||speed||Dexedrine, Benzedrine||Up to 2 days|
|Barbiturates||depressants / sedatives / hypnotics||downers, barbs, reds||Amytal, Fiorinal, Nembutal, Donna||
short-acting: 2 days
long-acting: 1-3 weeks
(based on half-life)
|Benzodiazepines||depressants / sedatives / hypnotics||bennies||Valium, Ativan, Xanax, Serax||
therapeutic dose: 3 days
chronic use: 4-6 weeks or longer
|Cocaine (benzoyl ecgonine metabolite)||Stimulant||coke, crack, rock cocaine||N/A||Cocaine urine test: Up to 4 days|
|Codeine||Analgesic / Opiate||N/A||N/A||2 days|
|Ethyl alcohol, ethanol||depressants / sedatives / hypnotics||alcohol, liquor, beer, wine booze||N/A||
urine: 2 to 12 hours
serum/plasma: 1 to 12 hours
|Heroin||Analgesic / Opiate||smack, tar, chasing the tiger||N/A||2 days|
|Hallucinogen||pot, dope, weed, hash, hemp||Marinol, Cesamet||
Single use: 2 to 7 days
Prolonged, chronic use: 1 to 2 months or longer
|Methadone||Analgesic / Opiate||fizzies||Dolophine||3 days|
|Methamphetamine||Stimulant||speed, ice, crystal, crank||Desoxyn, Methedrine||Up to 2 days|
|Methaqualone||depressants / sedatives / hypnotics||ludes, disco bisquits, 714, lemmons||Quaalude (off U.S. market)||Up to 14 days|
|Stimulant||ecstacy, XTC, ADAM, lover's speed||N/A||Up to 2 days|
|Morphine||Analgesic / Opiate||N/A||Duramorph, Roxanol||2 days|
|Phencyclidine||Hallucinogen||PCP, angel dust||N/A||8-14 days, but up to 30 days in chronic users|
|Propoxyphene||Analgesic / Opiate||N/A||Darvocet, Darvon (all forms of propoxyphene withdrawn from US market in November 2010)||6 hours to 2 days|
*Note: This table should be used as a general guideline only. Many variables may affect the amount of time that a drug remains detectable in the urine or other biological samples, as noted by LabCorp and in the Drugs of Abuse Reference Guide.
How long does alcohol stay in urine?
Some employees may ask does alcohol show up on a drug test? Alcohol has a short half-life in the urine. A urine drug test for alcohol may detect alcohol for 2 to 12 hours.
Results from workplace drug testing are fairly quick and can usually be received in a few days. An employer may also request to have the test done with a rapid test that can provide results on the same day. 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 typically contact the employer with the results. If a positive result occurs, a MRO will contact the applicant for further questioning. It is important to notify the laboratory or MRO of any medications currently in use, including prescription, over-the-counter or herbal medications. The applicant may have to provide proof of a valid prescription and prescriber information for prescription medications.
A concern for anyone undergoing drug testing is the possibility of a false positive result. Initial screening drugs tests may infrequently result in false positive results, although confirmatory (GC-MS) testing greatly lessens the chances of a false positive - reducing the risk to close to zero.
It is important that a person undergoing drug testing complete an accurate history of all prescription, OTC, and herbal drug use prior to the time of the sample collection. Certain substances, over-the-counter (OTC) or prescription drugs may result in false positives due to cross-reactivity with other substances, although many assays have been reformulated to avoid these possibilities.
Do poppy seeds cause a false positive drug test?
Poppy seeds and dextromethorphan have been reported to lead to a false positive result for opiates. Decongestants (ephedrine) have been implicated in causing false positives for amphetamines. The body metabolizes codeine to morphine and both substances may be found upon testing.
What can cause a false positive for cocaine?
If benzoylecgonine, the main metabolite of cocaine is detected, the person cannot claim that the result is a false positive due to Novocaine or any other "-caine" type of drug. Benzoylecgonine is only found in nature as a metabolite of cocaine, and there would be no other valid reason for it to be present in a drug screen. As previously mentioned, confirmatory testing with GC-MS will identify individual drugs or metabolites in a sample, and almost eliminate the chance for a false positive result. (Doering, et al)
Does passive smoke inhalation cause a false positive for marijuana?
"Passive" smoke inhalation from being in a room with people smoking marijuana is not considered valid, as the cut-off concentrations for lab analysis are set well above that which might occur for passive inhalation.
Other abnormalities in the urine screen may indicate that results may be a false negative or that there was deliberate adulteration of the sample. For example:
- a low creatinine lab value can indicate that a urine sample was tampered with; either the subject diluted their urine by consuming excessive water just prior to testing, or water was added to the urine sample.
- creatinine levels are often used in conjunction with specific gravity to determine if samples have been diluted. To help avoid this problem, the testing lab may color the water in their toilet blue to prevent the sample being diluted with water from the toilet.
- subjects may also attempt to add certain enzymes to the urine sample to affect stability, but this often changes the pH, which is also tested.
All of these variables, and others, are looked at in the lab analysis.
In some labs, patients who receive a positive result may have the option to pay for an independent retest of the urine sample that was originally submitted. A new urine sample is not allowed for the retest as the drug in question may have been excreted from the body by that time.
The results of drug testing should remain confidential and kept separate from the regular employee work file.
Can Employers Still Drug Test in States Where Marijuana Is Legal?
Yes. Legal rules vary from state to state where marijuana is now legal for recreational use. Also, as marijuana stays in the system over a prolonged period of time, the employee may use marijuana legally, but be drug tested at a later time and lose their job. In general, according to Law360, marijuana legalization laws in states where it is legal support employers in drug testing for marijuana use and firing people for it. Marijuana use is still illegal under federal law, and many employers prefer to maintain their drug-free workplace policies.
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- Toxicology Drug Testing
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- Substance Abuse and Mental Health Services Administration (SAMHSA). State List of HHS Certified Laboratories and Instrumented Initial Testing Facilities. Updated April 03, 2017. Accessed May 1, 2017 at https://www.samhsa.gov/sites/default/files/workplace/state-certified-labs-list-april-2017.pdf
- Wagner E. Can Employers Still Drug Test Where Marijuana Is Legal?. Accessed May 1, 2017 at https://www.law360.com/articles/874547/can-employers-still-drug-test-where-marijuana-is-legal
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Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.