Will a Medical Marijuana User Test Positive?

The short answer is, it depends. Allow me to get slightly technical as I explain.

Marijuana contains over 400 chemicals, including over 60 cannabinoids. The most prevalent and widely studied cannabinoid is delta-9-tetrahydrocannabinol, or simply THC. THC is best known for causing the euphoria that recreational users seek. THC can also be intoxicating, leading to a state of diminished motor control, thought control, and behavior control. It is this impairment that concerns employers.

Like the Animal Kingdom, plants within the Plant Kingdom are categorized according to their phylum, class, order, family, genus, and species. The words “Marijuana” and “Hemp” refer to the purpose of the cannabis species and also the concentration of THC. Marijuana contains greater than 0.3% THC and is typically consumed for its euphoric and/or therapeutic effects. Hemp contains no more than 0.3% THC and is typically used in the food and textile industries. “Cannabis” is a broader, scientific term that refers to the genus.  Medical cannabis may contain 0% THC.

As discussed in my article, “Drug Testing 101”, drug tests look for evidence of drug use. The most abundant marijuana metabolite indicating marijuana use is 11-nor-9-carboxy-delta-9-tetrahydrocannabinol. Thankfully there’s a shorter version: Carboxy THC. Carboxy THC is an inactive metabolite, giving a test interpreter no insight into a user’s level of impairment, if any.

Because marijuana has long been a federally controlled substance, and Schedule I substance since 1970, employers historically didn’t need to know if users were actively under the influence of marijuana, they just needed to know if there was any use. Any use alone was enough to not hire or terminate. State laws are changing things.

In the state where I currently reside, Pennsylvania, marijuana can be a legal medication option for patients who possess a “serious medical condition” (federal employees excluded). However, because it is still marijuana, by definition all medical marijuana products in Pennsylvania must contain at least 0.3% THC. So, any user of medical marijuana in Pennsylvania will produce the metabolite carboxy THC, and thus can (and often do) test presumptive positive on most workplace drug tests.

If the individual who tests presumptive positive does not have a valid prescription ID for medical marijuana, the test is confirmed positive. If the individual who tests presumptive positive does have a valid prescription ID for medical marijuana, the test is confirmed negative. If observable signs of impairment specific to marijuana (bloodshot eyes, heavy eyelids, slow movements, etc.) triggered a “reasonable suspicion” drug test, the result may be a positive.

To complicate things further, add to the equation other state laws, job function, the ADA, MRO interpretations, and company-specific policies and panel cut-off levels, and I’m sure you can understand why my answer to the title question remains, “it depends”.

In summary, any user of marijuana, recreational or medical, has some level of THC in their body. This doesn’t mean that they’re impaired, but does mean that they could test positive.

Ryan West