Drug testing for a job: 4 things you need to know

A healthy living blog from Marshfield Clinic Health System

Drug testing for a job: 4 things you need to know

Nov 13, 2023

Pre-employment drug testing helps determine if a job candidate uses illegal or prohibited substances. It’s common for employers to require a job candidate to complete a drug test. The job offer may be contingent on the results of the drug test and the candidate’s ability to pass.

What do the tests screen for?

Drug tests most commonly screen for the following drugs:

Methamphetamine (such as meth)
THC (such as cannabinoids or marijuana)
Cocaine
Opiates (such as heroin, opium, morphine)
Phencyclidine (such as PCP)

You may be tested for others if needed or determined by the prospective employer.

Screening can be done through urine, hair, blood and saliva samples. Urine is the most common and is mandated for regulated drug tests, which includes tests through the U.S. Department of Transportation when obtaining a CDL.

Drug testing graphic with sample cup — Although individuals may try to change drug test results through diluting water or bringing in other urine samples, it’s not easy to tamper with the process.

The drug testing process is thorough

Although individuals may try to change drug test results through diluting water or bringing in other urine samples, it’s not easy to tamper with the process.

Testing the sample includes measuring water levels, testing for different chemicals, checking the temperature and testing for specific gravity and creatinine, a by-product of metabolism. These checks monitor for things outside of normal sample parameters, which would cause a specimen to be rejected.

“There are rigorous standards testing goes through to determine positive or negative results,” said Dr. Michael Curtis, Marshfield Clinic Health System occupational medicine physician. “There is no room for tampering or concerns with integrity of our testing.”

Drug testing samples go to a Clinical Laboratory Improvement Amendments (CLIA)-certified lab. This means that clinical labs must be certified by the Center for Medicare and Medicaid Services (CMS) and are heavily regulated. Labs must pass certification before they can accept samples for testing.

“This means it’s virtually impossible for a lab to give incorrect results,” said Dr. Curtis.

Once you’re exposed, the drug remains in your body for longer than you might think

Most illicit drugs are still detectable in your urine for several days after last use, while THC may still be detectible for weeks or months.

In hair follicles, the longevity is even greater.

“Most drugs or the byproducts of their metabolism get incorporated into hair follicles and can be detectable in extremely small quantities for many months, far longer than urine detection for most substances,” said Dr. Curtis.

It’s also important to note that if your hair follicles absorb certain drugs, they aren’t easily washed off. If you are in a room where people are smoking marijuana or cocaine, it could show up in a hair test, even if you didn’t smoke any and washed your hair afterwards.

What does it mean if you test positive?

If your drug test result is positive, a Medical Review Officer (MRO) will determine if you have a prescription for the drug. If you don’t, your employer may conclude that you abuse drugs.

“Most of the time, the MRO only reports a positive drug screen to the employer. Exceptions include reporting drug abuse to professional licensing boards, in cases like physicians or nurses, or the Federal Motor Carriers Safety Administration for violations of their rules against drug abuse,” said Dr. Curtis.

If you test positive and are not a federally-regulated employee, the results will only go to your prospective employer. That test result will not get reported to an agency or outside organization or stay on your record.

No matter how the drug specimen got in your body or was ingested, a positive is a positive.

“It doesn’t matter how you ingested it, it’s in your body. We understand there are accidental exposures, but you will test the same and it will be recorded the same,” said Dr. Curtis.

Most organizations set their own policy for drug testing, regardless if the state has legalized marijuana. This means if you receive a positive test result, there is likely a certain amount of time required before you can re-apply. Talk to the organization you are interested in working with for more information.