Cannabis Saliva Detection Times
Drug testing for Cannabis
The choice you make in selecting either saliva or urine drug test kits for Cannabis makes a big difference.
Urine cannabis tests are by far the most reliable method in practical real world testing environments. This is because the breakdown products or metabolites of THC are reliably and slowly excreted in urine in high levels, making screening easy and reliable. Urine drug tests will turn positive within 90 minutes of THC use, and stay positive for an average of 3-5 days even after a small, single use of the drug.
Compare this to saliva cannabis drug testing. These now screen for the parent drug or compound, in the case of Cannabis this is THC delta 9 and 11.
Why not screen for the THC metabolites in saliva?
Well they simply don't make it reliably into saliva, so they cant be used as a marker.
Realising this back in the early development of these oral fluid drug tests, drug test manufacturers moved to develop drug tests which would detect the base compound or parent drugs.
These compounds are inhaled as THC is smoked. Saliva drug tests work by detecting these parent compounds directly, so simply soaking the collector in saliva wont work, to pick up these parent compounds the collector needs to be worked around the whole oral cavity to literally collect the THC deposits and THC residue to feed into the drug test.
How long will THC be detected on an oral drug test after use
Studies have determined that after smoking an average size and strength Cannabis joint, these residues are detectable for a window of up to 8 to12 hours. The cut off level for detection of 12 ng/ml was selected to give a laboratory level of overall accuracy of 96% compared to GC/MS saliva testing (laboratory standard).
However what if the mouth has been washed, or the the person being drug tested has eaten or drank since taking THC? Well in this case the drug test results may well be negative.
If the THC is removed from the oral cavity or reduced to below 12 ng/ml then the result will shown negative, this is why the detection window for THC in saliva is so short, simply put, the longer you go after smoking the Cannabis the less parent compound THC is left to detect.
Correct procedure is essential with an oral drug test kit when testing for THC
Swabbing the collection sponge really well all around the oral cavity is also a critical procedural element to getting the residual parent compounds into the test. Simply collection fresh saliva, even immediately after smoking without swabbing should result in a negative result.
What if the THC was not smoked but eaten or swallowed?
Then saliva THC testing would normally be negative as most of the THC parent compounds are trapped in solid components and little residue deposited in the oral cavity.
Will a saliva drug test detect passive Cannabis smoking
The 12ng/ml cut off level of saliva tests is a lot lower than the 25 or 50ng/ml cut off level of urine tests, will it detect passive smoking?
No is the short answer, as we have explained they are not testing for the same markers, but the 12ng/ml saliva cut off was chosen to always exclude the possibility of passive exposure as mitigation for a positive result.
How accurate are saliva drug tests?
Nothing in rapid drug testing is 100%, and no drug test manufacturer claims to offer the accuracy of laboratory GC/MS testing.
In saliva and urine drug testing in the workplace we always recommend confirming all non negative test results using an accredited laboratory confirmation service. Lab drug test packs for both saliva and urine drug confirmation testing are available from the ukdrugtesting web site to enable everyone to access this service.