Science Revisited: Will Using CBD Hemp Oil Lead to a Positive Drug Test for THC?

You may recall part one of our now two-part series that explores whether a person using CBD hemp oil could test positively for THC or marijuana. The study cited concluded the following:

Article by PlusCBD Oil

“…a consumer who uses a high-quality, scientifically vetted hemp-based product at the standard serving size is highly unlikely to test positive for THC and/or THC-COOH. However, it’s important to be cognizant that extremely high doses may result in a positive urine screen (that would be subsequently shown to be false via GC/MS). “

An additional study conducted by Leson, et al dove further into the subject, examining the effects of THC administration on subjects who had positive drug screens for THC. What were their findings, and do they align with Part 1’s findings or contradict the initial study’s results?

The Latest Study

Leson and colleagues’ recent study involved 15 adult subjects (10 females, 5 males) who had not previously been exposed to THC. The subjects were given single daily THC doses in an oil matrix, ranging from 0.09 to 0.6 mg, over four successive 10-day periods. Their urine samples were screened for cannabinoids using radioimmunoassay, a method of measuring very small amounts of a substance in blood.

Unfortunately, radioimmunoassay is prone to producing false positives, and it confirmed the presence of THC-COOH. The radioimmunoassay results showed that daily ingestion of up to 0.45 mg of THC in an oil matrix did not screen positive at a 50 ng/mL cutoff. When the daily intake was increased to 0.6 mg, one sample screened “positive”. At the lower cutoff level of 15 ng/mL (which is used by some employers, law enforcement agencies, and drug treatment programs), 19% of urine samples screened “positive” for THC.

However, when the samples were analyzed using gas chromatography-mass spectrometry (GC-MS), an analytical method of identifying different substances within a test sample, none of the samples screened positive. In fact, under the GC-MS method, the highest value obtained was only 5.2 ng/mL, well below the lower cutoff level of 15 ng/mL.

The researchers concluded the following:

“Practicing routine GC-MS confirmation of urine specimens screening positive appear to minimize the risk of producing confirmed positive urine tests from hemp oil.”

So there you have it. If you keep your consumption of CBD-rich hemp oil to less than 200 to 300 mg per day, you are highly unlikely to screen positive for THC use via the confirmatory (and most important) GC-MS test. Therefore, less than 100 mg to 150 mg daily is very unlikely to result in a positive preliminary immunoassay-screening test.


But Wait, There’s More

One caveat is that CBD, THC, and other cannabinoids are known to interact with a subclass of a very important family of enzymes known as the cytochrome P450 group (abbreviated as CYP). CBD is known to inhibit the same P450 enzymes that are known to metabolize it, and some of these enzymes (e.g., CYP3A4 and CYP2C9) are also responsible for THC metabolism along with the hepatic metabolism of ~ 60% of clinically prescribed medications. Co-administering cannabis and CBD may cause THC levels to be elevated to a greater extent, for a prolonged period of time.

Medical marijuana patients who utilize high doses of CBD concentrates should keep in mind that there are multiple potential drug interactions. Moreover, there is also the issue of pharmacogenetics– the degree of variability with which an individual’s genetics causes differences in drug metabolic pathways, which can affect how someone responds to the therapeutic benefits as well as adverse effects of drugs. Hence, the actual dose that causes a potential “positive” screen or confirmatory test for THC from consumption of CBD-rich hemp oil will change from one individual to another due to these genetic differences in the CYP450 enzyme system.

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