Last updated : July 14, 2025
No matter which testing method you’ve chosen—hair, urine, or saliva—you receive the same drug testing results. Of the three results, two are very straightforward. The inconclusive result, however, is a little more complicated. Let’s break down the specifics of drug testing results.
All laboratories that process drug tests are prepared to perform two tests on a specimen. The first test is a type of immunoassay test. If the specimen tests positive for drugs, it undergoes a second test. The gas chromatography/mass spectrometry (GC/MS) test confirms the IA test result in urine and saliva test samples. It also records the drug level.
The liquid chromatography/mass spectrometry (LS/MS) test yields the same result in hair tests but it takes a bit longer to receive the results.
Negative test result
Although drug use is likely in every industry, it’s not the norm by any means. The majority of employee drug tests return with a negative result.
A negative drug test result is evidence that there are no drugs in the system.
However, the urine test can occasionally yield a false negative result. That’s because urine tests require the privacy of a restroom to collect the test sample. Some employees are “lucky” enough to make it through the test having substituted or tampered with the sample.
Possible ways to falsify the urine drug test are:
- Substituting the specimen with someone else’s or synthetic urine
- Diluting the specimen
- Adulterating the specimen
There are companies that claim they have developed products that detoxify the body—that’s code for “mask drug use.” However, these products usually contain very specific directions and failure to follow them to a “t” result in a failed test.
The instructions include drinking specific amounts of water and even urinating “x” number of times prior to the test. Odds are that if it “worked,” it was merely because a diluted specimen went undetected.
Positive test result
When a drug test returns with a positive result, it detected drugs.
Employers who drug test have policies in place outlining the process to follow when an employee tests positive for drugs. Many companies mirror their drug testing policies after those of the DOT.
The DOT (Department of Transportation), requires that an MRO (Medical Review Officer) review all test results. Positive results warrant contacting the employee to inform them of the result. The employee is given a chance to explain any medical reason that would cause a positive result. This includes a written statement from their physician explaining why the medication was prescribed. The statement should also document why the physician believes it’s okay for the employee to keep working while taking the drug.
If the employee’s explanation and evidence are accepted by the MRO, the test result is changed to negative. The MRO reports their findings to the company representative who then reports the findings to the employer.
A safety-sensitive employee who tests positive for drug use is immediately removed from service. They aren’t allowed back to work until completing the return to duty process which includes successfully completing a rehabilitation program and a negative drug test result.
Someone employed in the general workforce may simply be terminated rather than suspended until completing a “return to duty” process. However, we’ll note that ultimately it’s left to the safety-sensitive employer whether or not the employer returns to work at the same company.
Last chance
Last chance agreements, also called second chance agreements, are becoming more popular among employers though. These agreements basically state that an employee failing a drug test won’t lose their job if they follow certain conditions of continued employment. Moreover, they’re often written to reflect a specific set of conditions. For instance, someone who tests positive for marijuana use may not follow the same steps as someone who has tested positive for heroin and exhibits signs of a serious addiction.
Furthermore, some states have laws in place that prohibit employers from terminating an employee who comes to them admitting they have a substance abuse problem—if the employee is seeking help for the first time.
Inconclusive test results
The inconclusive result in itself is simple to define. The test couldn’t determine either a positive or negative result.
It’s the why of it all that contains different information regarding this test result though.
Adulterated or substituted specimens
Laboratory equipment has become increasingly sophisticated and laboratory technicians have long been wise to the drug communities’ attempts to falsify employee drug test results.
Adulterated or substituted specimens include the following:
- Synthetic urine—This is the most recent wave of “beat the test” technology. Synthetic urine was discovered by accident but serves its place in the scientific community. However, somewhere along the way, manufacturers discovered the benefit of promoting the sale of the stuff as a means to pass urine drug tests. It’s illegal to manufacture or sell synthetic urine in many states.
- Positive dilute—When this explanation accompanies an inconclusive drug test result it means that even though the specimen contained too much water, there were also drugs detected. It also points toward the fact that the employee may have been trying to mask drug use. Employers follow company policy that dictates steps taken in the event of a positive drug test result.
- Negative dilute—A negative dilute explanation indicates that no drugs were identified, however, the specimen contained too much water. Again, employers often assume the employee was trying to mask drug use. Some companies request the employee to immediately submit to a second drug test. If given the opportunity to retake the test, employers view a refusal to test as grounds for termination.
Drug testing results in a safer workplace
There’s no question that companies that drug test employees deter drug use in the workplace. Most employees value their jobs and won’t risk occasional drug use when they know their employer drug tests.
It’s just not worth the risk.
Some employees might not be able to refrain though. Addicts are well-known for rationalizing their drug use. They may not even have admitted to themselves that they have a problem even when it becomes blatantly evident to everyone around them.
Employers that drug test want to make their work environment as safe as possible for everyone. Likewise, they have the opportunity to point an employee who’s tested positive for drugs toward help.
A kind word showing that you truly care about your employee’s well-being, even if it’s while explaining your reason for termination, could inspire them to seek help for their problem.
