CBD and hemp oil are increasing in popularity. But what is the risk that they could cause a positive drug test for THC?

With the increasing popularity of cannabidiol (CBD) supplements, I have been getting a LOT of questions about whether it may lead to a positive drug test. This is completely understandable. Who wants to get busted on a drug test when they’re not even getting high?

Several other people have already addressed this question:

• Herb: Will CBD Oil Show Up On A Drug Test?
• Leafly: Does Using CBD Hemp Oil Result in a Positive Drug Test for THC or Marijuana?

My immediate reaction was to say that it is unlikely, but I wanted to explore it further. There are actually three ways in which it is theoretically possible for CBD (which is typically consumed as hemp oil) to cause a positive on a urine test for THC:

• CBD itself could cause a false positive
• CBD could convert to THC in your body
• Trace amounts of THC in hemp oil could cause a positive

I’ll examine each of these possibilities to see if it is possible that CBD could cause a positive, or if we can shut this down for good.

 

Can CBD Cause a False Positive on a Urine THC Test?

This question is difficult to answer, since it depends on details of the test that are not always made public.

The first type of urine test is called an immunoassay, which uses an antibody to detect THC metabolites. This test will actually detect anything that the antibody binds to. Often, antibodies can bind to related molecules, and there is a metabolite of CBD that is very similar to the metabolite of THC that these tests detect.

Several assays have examined whether CBD can cause a false positive and shown that it doesn’t (saliva assay, urine assay #1, urine assay #2). However, for the urine tests, they should have really tested for false positive from CBD metabolites, not CBD itself. After all, it is the CBD metabolites that go into the urine.

The second step after a positive result in the immunoassay is to confirm it with a GC/MS test. This test does not rely on an antibody and is much less likely to cause false positives. In theory, this test should not detect CBD metabolites, but this highly depends on the exact methods of the assay. I could not find any information on whether these assays have assessed the possibility of false positives by CBD metabolites.

Conclusion: It is very unlikely, but not totally impossible that CBD metabolites cause a false positive on urine THC tests. There is a recently finished clinical trial which will actually assess whether THC metabolites are detected in subjects who consume CBD. This could help answer this question.

 

Can CBD Be Converted to THC In The Body?

The next possibility is that your body can convert CBD to THC. This may sound unlikely at first, but actually CBD does convert to THC in acidic environments.

In 2016, it was proposed that stomach acid could convert CBD to THC in high enough levels to have a pharmacological effect (and potentially fail a drug test).  Obviously this would only apply if you are taking CBD orally and not if you are vaping it.

This was controversial and other groups pointed to animal studies and human studies to argue that no significant amount of THC is formed.

Conclusion: It is very unlikely that a significant amount of THC is formed in the stomach from CBD. Nonetheless, you can take CBD after a meal instead of an empty stomach if you are worried. This will raise the pH of your stomach. You should really be doing this anyways, since it can boost CBD absorption by 4 to 5 times.

 

Is There Enough THC in Hemp Oil to Cause a Positive Urine THC Test?

The final possibility does not directly involve CBD. However, most CBD is taken as hemp oil, which does contain some trace amounts of THC. The 2014 Farm Bill set a limit (0.3%) on the amount of THC that can be present in legal industrial hemp. 

In a 2001 study, 15 subjects consumed daily hemp oil with different levels of THC. At 0.45 mg/day, no subjects tested positive. At 0.6 mg/day, one subject tested positive with a urine concentration of 5.2 ng/mL. This dose would correspond to ingesting about 200 mL of hemp oil per day, assuming the limit of 0.3% THC.

Conclusion: It is very unlikely that you will test positive for THC from taking hemp oil, but not impossible. You would have to be taking really high daily doses of hemp oil (like 200 mL and up) and also need to be one of the unlucky people that naturally produces a lot of the THC metabolite detected by urine tests.