Blog - Beach House Rehab Center
February 15, 2019

How Does a Drug Test Work?


If you’ve heard from your employer or a prospective employer requires a drug test as a precondition for employment, you may well wonder what the drug test entails, the process involved, what type of test will be performed. Specifically, how does a drug test work?


A drug tests screens for the presence of drugs in your system. These screening tests check for illicit and prescription drugs. Drug tests include urine, blood, hair, saliva, or sweat. While many different drugs can be tested, the drugs most often tested for include amphetamines, barbiturates, cocaine, marijuana, phencyclidine, opioids, and steroids.


You may need to take a drug test as a condition of employment, either as a pre-screening prior to getting hired, or as part of mandated random drug testing during employment. College and professional athletes may be required to undergo drug testing in order to participate in team sports. A drug test may be required during police investigations and court cases. A healthcare provider may require a drug test if drug abuse is suspected, or as part of compliance monitoring during treatment. A doctor who prescribed opiate medications to treat a patient’s pain may order a drug test to ensure the right painkiller dose. 


Urine, saliva, blood, and hair testing are the different types of drug tests.

Urine – The urine drug test is the most common drug test type requested by employers to test their employees for drug use. Urinalysis shows the presence of a specific (requested) drug in the system after the drug’s effects have worn off, although this varies by drug. Employers typically request the urine drug test to screen for alcohol, amphetamines, cocaine, marijuana, methamphetamine, nicotine, and opiate narcotics (such as oxycodone or heroin).

Saliva — An employer may wish to find out about recent drug use, for example, and saliva (oral) testing may be requested for this purpose. Saliva drug tests can detect usage from a few hours to up to 3 days, but are not the best test to determine long-term drug use. Advantages of saliva drug test is that samples are easy to gather, there’s less likelihood of adulterated samples, and it can be tested for the presence (recent use) of alcohol, amphetamines, cocaine, marijuana, and methamphetamines.

Blood – Some employers want to know what drug(s), if any, are present in their employee at the present time. For this purpose, a blood drug test may be requested. Although more invasive than saliva drug test, a blood drug test — which can also be conducted in a hospital emergency room to detect toxins (toxicology test) — can screen for the presence of alcohol, amphetamines, cocaine, marijuana, methamphetamine, nicotine, and opiates.

Hair – A hair drug test is more useful to determine longer-term drug use, generally more than a 90-day time period. Drugs that can be tested in a hair drug test include alcohol, cocaine, marijuana, methamphetamine, opiates, and phencyclidine.


A urine drug test generally requires you to submit a urine sample at a specified lab. In some cases, a lab technician or other medical staff member will need to be present during the sample collection. You will be given specific instructions regarding the sample collection and the process is quick and easy to follow. After sample collection, the lab takes the sample to perform the requested tests for the presence of various drugs (generally specified by the entity requesting or requiring the drug test).

When a blood test for drugs is required, you will go to a specified lab for collection of the blood. A lab technician will insert a small needle into a vein in your arm and collect the vial(s) of blood for the drug test. While this procedure usually involves a brief sting as the needle is inserted and withdrawn, the process is quick and otherwise painless. The area will be sterilized with alcohol and a small Band-Aid or compression wrap over a cotton ball will be applied.


According to, there are two steps most commonly used in a certified drug test process. The first is the initial (immunoassay), and then a gas chromatography-mass spectrometry (GC-MS) for confirmation. Using this combination helps ensure that there is a high level of specificity and sensitivity for the drugs tested. What the means in layman’s terms is that there’s a much less chance of a false positive from the tests. Since the initial immunoassay is performed first, if the results come back negative, no further testing is required. If the test results are positive, lab technicians perform the GC-MS test to confirm what the immunoassay found. The GC-MC test is done using a separate portion of the biological sample. It is used to confirm individual drug substances or metabolites as well as quantify the amounts of the substances found.


The amount of time that drugs can be detected in the system – such as how long specific drugs can be detected in a urine sample – varies quite a bit depending on the substance. In urine drug testing, the amount of time a drug/metabolite remains in the body differs according to various factors:

  • Amount and frequency of use
  • Metabolic rate
  • Body mass
  • Age
  • Overall health
  • Drug tolerance
  • Urine pH

Specific Drug Detection Times

The lower and upper boundaries for drug detection times for the specific drugs listed here are as follows:

  • Alcohol – 24 hours or less
  • Amphetamines – up to 2 days
  • Barbiturates (short-acting) – 1-3 days
  • Barbiturates (long-acting) – 1-3 weeks
  • Benzodiazepines (short-term therapeutic use) – 1-3 days
  • Benzodiazepines (chronic use) – 4-6 weeks or longer
  • Cocaine – up to 4 days
  • Codeine – 2 days
  • Heroin – 2 days
  • Marijuana (THC), (casual use) – 2-7 days
  • Marijuana (THC), (long-term/chronic use) – 1-2 months or longer
  • Methadone – 3 days
  • Methamphetamine – up to 2 days
  • Morphine – 2 days
  • Opiate – 1-5 days
  • Oxycodone – 1-4 days


A 2018 analysis by Quest Diagnostics, a company that’s conducted drug tests for 30 years, found positive drug tests in the American workforce is at its highest rate in a decade. Quest Diagnostics’ analysis examined more than 10 million drug test results.

Cocaine — The rate for cocaine positivity in the overall U.S. workforce was up for the 5th year in a row, with rates up 7 percent in 2017 for urine testing (the most common drug test specimen type), and also up 16 percent year-over-year in oral testing, and up 19 percent in hair testing. More troubling, however, is the dramatic uptick in cocaine positivity in the general workforce in 4 of the past 5 years in 5 states: Nebraska (with a 91 percent increase between 2016-2017), Idaho (up 88 percent), Washington (a 31 percent increase), Nevada (up 25 percent), Maryland (a 22 percent increase), and Wisconsin (up 13 percent).

Methamphetamine – Positivity rates for methamphetamine in the general U.S. workforce has skyrocketed in the Midwest and South regions of the country:

  • East North Central division of Midwest – up 167 percent (comprising the states of Illinois, Indiana, Michigan, Ohio, and Wisconsin)
  • East South Central division of South – a 160 percent increase (comprising states of Alabama, Kentucky, Mississippi, and Tennessee)
  • Middle Atlantic Division of Northeast – up 150 percent (area comprises New Jersey, New York, and Pennsylvania)
  • South Atlantic division of South – up 140 percent (Delaware, District of Columbia, Florida, Georgia, Maryland, North and South Carolina, Virginia, and West Virginia

Marijuana – The Quest Diagnostics analysis found marijuana positivity continuing its 5-year upward trajectory in urine testing (in general U.S. workforce and in safety-sensitive federal workforce). The overall positivity rate for marijuana increased 4 percent in the general U.S. workforce (2.6 percent in 2017 versus 2.5 percent the year before), and nearly 8 percent in federal safety-sensitive workforce (0.84 percent in 2017 versus 0.78 in 2016). In states where recreational  use of marijuana is legal (by state law; marijuana is still illegal by federal law), there were significant jumps in marijuana positivity: Nevada (up 43 percent), Massachusetts (a 14 percent increase), and California (increasing 11 percent). Workers in federally-mandated safety-sensitive jobs are required by the Department of Transportation to undergo routine drug testing, and in three states, marijuana positivity showed significant increases: Nevada (39 percent), California (20 percent), and Massachusetts (11 percent).

Opiates – On a national basis, opiate positivity rates for the general U.S. workforce declined 17 percent between 2016-2017 in urine drug testing. Specifically, oxycodone positivity decreased 12 percent, hydrocodone positivity went down 17 percent, and hydromorphone positivity declined 22 percent. Companies typically test for prescription opiate drugs and semi-synthetic ones, but don’t typically test for the presence of fentanyl and synthetic analogs of fentanyl.


While you wait for the results of the drug test, you might be a little anxious about what will be found. Did the poppy seed bagel you eat that morning affect the results? What about your prescribed painkiller that you take only as directed? The answer is yes, poppy seeds, over-the-counter medications, and prescription drugs can lead to false positives. If you’ve been sick, could that affect your drug test results? And what about the beers you drank during a get-together last weekend to watch the football game? If you know you’ve smoked marijuana (and it’s not medical marijuana prescribed for you, or you aren’t in a state allowing recreational or medical marijuana), what happens then? If you have specific concerns, talk with your doctor about them.

There’s really nothing you can do about the tests for now, so it’s best to be optimistic about the results. The testing facility will only test for the presence of drugs specified by the requesting entity – your prospective or current employer, the sports organization you belong to, your doctor, or the courts or other investigative agency.

If the drug tests come back negative, that means one of two things: either there weren’t any drugs in your body, or the level of the drugs tested for was under the established level. This level, of course, depends on the drug. The tests may come back positive, which means your drug tests results showed the presence of one or more drugs above the established level.

It’s important to note that false positives do happen. When this happens, you’ll be required to have a second drug test to rule out the presence of drugs in your system. What they’re looking for is to determine whether or not you’re actually taking the drugs.

For more about drug testing, drug abuse, addiction and recovery, check out these articles:

Common Forms of Prescription Drug Abuse and Their Dangers

Dangers of Snorting Prescription Drugs

Do I Need Cocaine Rehab?

Do I Need Marijuana Rehab?

Employer Drug Screening – What to Know

Long-Term Effects of Substance Abuse

Meth Addiction and Abuse Statistics

Painkillers Explained: Understand What Medications Doctors are Prescribing for Your Pain and How They Affect You

Prescription Opiate Detox: What to Expect from Withdrawal and Recovery

Opiate Addiction By the Numbers: Data You Can’t Ignore

Will Suboxone Show up in a Drug Test?  


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