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Vaping CBD Products Can Still Yield Positive Urine Drug Tests, Study Finds

By Leo Bear-McGuinness

Published: Nov 05, 2019   
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Vaping low THC/high CBD cannabis can still lead to a positive THC result on a urine drug test, according to a small study of six adults from Johns Hopkins Medicine.

After vaping cannabis that contained 0.39 percent THC, one third of the study’s participants tested positive on a standard urine test similar to those used for employment-related or criminal justice-related drug testing programs.

Does CBD show up in drug tests?

Published in the Journal of Analytical Toxicology, the study supplied three women and three men with some 27:1 CBD-to-THC cannabis material – a ratio often found in legal hemp and CBD products.

The participants then vaporized just less than 1 gram of cannabis, which contained a total dose of 100 milligrams of CBD and 3.7 milligrams of THC. Two of the six participants subsequently tested positive for a cannabis metabolite.

The volunteers also vaped pure CBD and consumed pure CBD capsules, but these products didn’t incur positive urine results.

“These results suggest that pure CBD, used once by itself, will not cause a positive drug test,” Ryan Vandrey, an associate professor of psychiatry and behavioral sciences at the Johns Hopkins University School of Medicine, said in a statement.

While only a third of the study’s participants failed the test, the study’s authors claim their results demonstrate the risks THC-containing products can pose to anyone subject to a drug test. And in response, they’re calling for tighter regulations.

“Accurate labeling and regulation of ∆9-THC content in CBD/hemp products are needed to prevent unexpected positive drug tests and unintended drug effects,” they write in their summary.

Since the passing of the 2018 Farm Bill, the US Food and Drug Administration has defined hemp as any cannabis crop containing 0.3 percent THC or less in dry weight. Although the cannabis used in the study exceeds this limit by 0.09 percent, the authors say it was still hemp-like, which is why most consumers wouldn't expect to test positive for THC. 

“Because the market for CBD products is so new and the popularity of use is growing so quickly, we want the public to be aware that a positive drug test is possible," says Ryan Vandrey.

The end of testing

Cases involving accidental THC exposure from CBD products are not uncommon. Last month, the New York Times reported that a couple in Florida were once charged with marijuana possession after a CBD-infused gummy bear tested positive for THC, and another person was arrested for violating their parole after testing for THC, when they claimed to have only used CBD. 

“I have a hard time finding anyone who hasn't used a CBD product at least once, but most are completely unaware of the possibility of THC exposure or a positive drug test as a result of using these newly legalized products,” says Vandrey.

Many US workers, notably the 7-9 million employed by the federal government, are still required to pass a drug test. But as cannabis is now legal in some form or another in over 30 states, these workplace drug tests are starting to drop out of fashion.

Starting in 2020, employers in Nevada and New York City will no longer be able to reject a job applicant because of a failed pre-employment drug test for cannabis, thanks to new legislation brought in by state and city lawmakers. Courts in Connecticut, Maine, and Massachusetts have also found in favor of job applicants in cases where an employer has pulled its offer because the prospective employee tested positive for cannabis. 

But until cannabis is legalized at a federal level, any such employee or member of a criminal-related drug testing program still run the risk when consuming a cannabis product.

“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,” Tory Spindle, a researcher at the Johns Hopkins Bayview Medical Center, said in a statement.

“What this means is that people need to be wary of single-dose or cumulative THC exposure and be aware that these now legal products may cause an unexpected positive result on a drug test.”

Leo Bear-McGuinness

Science Writer & Editor

Leo joined Analytical Cannabis in 2019. From research to regulations and analysis to agriculture, his writing covers all the need-to-know news for the cannabis industry. He holds a Bachelor's in Biology from Newcastle University and a Master's in Science Communication from the University of Edinburgh.


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