How Long Does THC Stay in Saliva?

The late-1990s through early 2000s saw “considerable developments in the use of oral fluid (saliva) for drug testing,” and saliva-based drug tests are used for “testing in employees at workplaces where drug use has safety implications, in drivers of vehicles at the roadside and in other situations where drug impairment is suspected.”

While urine-based drug tests are still frequently used, saliva-based tests have gained popularity because they are considered less invasive and less susceptible to tampering relative to other types of drug tests.

In this article, we’ll walk through several factors that influence the level of detectable THC in your saliva and how long after consuming cannabis a saliva-based test is likely to come back positive.

Factors affecting THC levels in saliva

The top factor impacting the presence of THC in your saliva is whether or not you’ve recently consumed cannabis, and consumers who smoke or vape products containing THC face the highest risk of failing a saliva drug test.

As one 2010 study comparing THC levels in the saliva of occasional and regular cannabis consumers revealed, “the highest THC concentrations were always observed in the first oral fluid samples obtained 5 min after cessation of smoking.”

The same study found that frequent or “chronic” cannabis consumers had a higher concentration of THC in their saliva shortly after smoking — a finding that aligns with the common notion that long-term cannabis users are more likely to test positive for THC compared to less experienced users.

Still, the study’s authors note that the differences in saliva THC concentration between frequent and infrequent users become insignificant about 15 minutes after smoking. They attribute this change to the “more efficient smoking techniques” used by experienced users and the specific way THC shows up in a person's saliva.

How long does THC stay in saliva?

The good news for long-time cannabis users is that tests for detecting THC in saliva won’t pick up on consistent cannabis use over several months or years like a urine or blood test might. 

This is because, unlike many substances these tests are looking for, the THC concentration in saliva doesn’t reflect the THC concentration in the bloodstream. Instead, according to multiple reviews, the concentration of THC in saliva is primarily caused by “contamination of the buccal cavity,” (i.e., your mouth).

According to one peer-reviewed journal article, cannabis consumption will show up on a saliva-based test for as long as 24 hours. 

To put this in perspective in relation to other types of tests, the same article states that urine samples can reveal cannabis consumption from up to 30 days prior to the test, hair samples can reveal consumption from 90 days prior, and sweat samples can reveal consumption from between 7 to 14 days prior to the test.

With that being said, another (slightly older) study cites several examples showing “detection of THC in oral fluid for up to 24-72 hours after a single intake of cannabis” and, in its own investigation, found that THC was detectable in saliva as long as 8 days after consumption for 1 out of the 11 study participants.

How to pass a saliva test for THC

If you’re faced with a test designed for detecting THC in saliva, there aren’t too many options available for preventing detection — especially if you’ve consumed cannabis in the last two days or so. 

While one might think otherwise, actions such as eating a THC-free snack, brushing your teeth with toothpaste, or rinsing your mouth with mouthwash won’t significantly affect the results of a saliva drug test.

“The use of commercial adulterants or other products capable of acting as adulterants, such as Clear Choice®, Fizzy FlushTM, Spit and Clean®/™ mouth wash [sic] and Cool Mint Listerine® also had no substantial effect after 30 min,” the author of one review adds.

And, unlike with a urine test, it’s exceedingly difficult to swap out your potentially THC-rich bodily fluids with a clean or synthetic spit sample because saliva tests can be administered by or in the presence of a second party — presumably the person most concerned about whether or not you’ve consumed cannabis.

Because saliva tests can only detect THC for up to a few days after consumption, your best bet for passing a saliva-based drug test is to take a short break from cannabis, especially if you primarily smoke or vape.

On the bright side, pre-employment drug tests for cannabis seem to be waning in popularity alongside other aspects of the Reagan-style “War on Drugs” as cannabis is legalized in more and more U.S. states.

In fact, according to the American Bar Association, “Nineteen states and the District of Columbia have legalized recreational marijuana use. Three locations—New York City, Philadelphia and Nevada—have outright prohibited pre-employment marijuana testing in most industries.”

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