Cannabinoid Products May Lead to Cannabis-Positive Result in Urine Drug Tests


Approximately 2 out of 6 study participants tested positive after vaping cannabis that contained 0.39% THC using urine testing methods.

A small study of 6 adults has found that a single vaping episode of cannabis that is similar in chemical composition to legal hemp products could possibly result in positive results on urine drug screening tests commonly used by many employers and criminal justice or school systems.

In 2018, the United States Farm Bill legalized the production and sale of hemp. As a result, consumer hemp products, such as oils, vaping cartridges, and hemp flowers for smoking, can now be legally purchased in specialty stores, general retail stores, and through websites across the United States. Hemp is increasingly being used in medicine and wellness markets, particularly for cannabidiol (CBD), 1 of the more than 100 cannabinoids found in the cannabis plant.

In a paper published Nov. 4 in the Journal of Analytical Toxicology, the researchers reported that 2 out of 6 study participants tested positive after vaping cannabis that contained 0.39% THC using urine testing methods that are consistent with testing frequently performed for employment-related or criminal justice-related urine drug testing programs.

Based on the findings, postdoctoral fellow Tory Spindle, PhD, a researcher in the Behavioral Pharmacology Research Unit at the Johns Hopkins Bayview Medical Center, said that individuals should be wary of single-dose or cumulative THC exposure.

“People who use legal hemp products for medical intent rarely just use them once as we did in this study, and prior studies show that THC and its metabolites may accumulate with repeated use,” Spindle said.

The researchers recruited 3 women and 3 men with an average age of 31 years old. One participant self-reported as African American and the others were white. The cannabis used in this study contained 10.5% CBD and 0.39% THC, a 27 to 1 ratio of CBD to THC that is similar to that which is often found in legal hemp/CBD products, according to the study.

Researcher volunteers vaporized a little less than 1 gram of cannabis, which contained a total dose of 100 milligrams of CBD and 3.7 milligrams of THC. In addition to vaping the high CBD/low THC cannabis, study volunteers were also given pure CBD in a capsule, vaporized pure CBD, and placebo in 3 other dosing sessions, 1 week apart from each other. In all active drug conditions (except placebo), the CBD dose was 100 milligrams per session.

The drug testing cut-off used to determine a positive result in the study was a screening concentration of at least 50 nanograms per milliliter of THCCOOH, a metabolite that is used to determine whether a person has used cannabis, in the urine sample using a 1-site “dipstick” test. A positive on that test was then confirmed at a 15 nanograms per milliliter cut-off of THCCOOH using a more sensitive test method.

The research team indicated that they plan to repeat their studies using products that fall within the current federal hemp regulations with respect to THC content and also plan to study the impact of repeated CBD/hemp exposure on drug testing outcomes.


  • Some CBD Products May Yield Cannabis-Positive Urine Drug Tests [press release]. John Hopkins Medicine website. Published November 4, 2019. Accessed November 6, 2019.

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