The Elusive Test for Marijuana Impairment

Alcohol and marijuana are at opposite ends of the substance-testing spectrum. If an employee tests positive for alcohol at .04 BAC or higher, there’s a very good chance he or she is impaired. However, the employee who tests positive for marijuana may be impaired, or may have last smoked marijuana two weeks prior.

This can impact employers in ways that aren’t obvious. What if an employee tests positive after a car accident in which a non-employee was injured? And what if that employee had tested positive once before, but you gave them a second chance? You could be sued for negligently retaining a known pot-smoker without a shred of evidence that employee was impaired at the time of the car accident.

The police have a blood test at their disposal that, at least in theory, detects impairment by quantifying the amount of THC—the active ingredient in marijuana—in someone’s blood stream, rather than merely testing for metabolites in someone’s urine. While the limitations of this test have been the subject of news reports lately, it’s got to be better than urinalysis.

Trouble is, a lot of people don’t like needles, and I don’t know of a single employer that uses a blood test for drug detection.

With the legal status of marijuana evolving rapidly, employers desperately need a reliable method to detect impairment. We would like to hear from employers who have confronted this issue, and particularly anyone who uses blood tests to test for drug use.