Marijuana is an incredibly complex plant with a huge number of variations. Many of us are familiar with the basics: Marijuana contains THC and CBD. But there is so much more to marijuana than just those two cannabinoids. As of 2014, there have actually been ~545 identified chemical compounds in cannabis. Therefore, it would be near-impossible for a drug test to simply denote the casual or heavy use of the drug. Instead, urine and oral fluid testing for cannabis have very specific goals:
In an oral fluid test, the donor’s saliva is being tested for THC (the drug’s main psychoactive ingredient), and not CBD (cannabidiol), CBV (cannabivarin), CBC (cannabichromene), or any other cannabinoids. CBD is found in most hemp, and scientific studies have proven that it does not cause impairment, nor does it have the same psychoactive effect as THC. So if you consume hemp seeds, for example, which have a high CBD concentration, you will not test positive for cannabis on an oral fluid drug test. In order to test positive on an oral fluid test, there must be THC in your saliva.
If a donor is being tested via a 5 panel urine test, they are again being tested for the presence of a specific compound. Urine tests identify the presence of one of marijuana’s metabolites: THC-COOH. This means that the THC has been metabolized by your body, with the metabolite being the product of that process.
So while drug testing can indicate the presence of certain cannabinoids and THC metabolites in a person’s system, they cannot prove how often a donor uses it, how much the donor consumed, or whether or not they smoked, ate or vaped the drug. A urine or oral fluid test will, however, help identify recent use which can identify risk of impairment within the workplace.
Sharma, P., Murthy, P., & Bharath, M. M. (2012). Chemistry, metabolism, and toxicology of cannabis: clinical implications. Iranian journal of psychiatry, 7(4), 149-56. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3570572/
Wigmore, J.G., (2018). Wigmore on cannabis: The forensic toxicology of marijuana for lawyers and other medicolegal professionals. Toronto, ON: Irwin Law Inc.
White, R.M. Sr., More, C.M. (2018). Detection of Drugs and their Metabolites in Oral Fluid: A Volume in Emergin Issues in Analytical Chemistry. Elsevier Inc. DOI https://doi.org/10.1016/C2017-0-01839