Quick answer
Oral fluid, often called saliva, has two cannabis cutoff levels in federal workplace testing. The initial immunoassay screen is 4 ng/mL of THC. The confirmatory test by mass spectrometry is 2 ng/mL of THC. Device makers who sell roadside and workplace kits use other numbers, from 10 ng/mL to 25 ng/mL. A cutoff is the concentration that separates a negative from a positive.
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Federal cutoffs
The Department of Health and Human Services sets the numbers. The Substance Abuse and Mental Health Services Administration publishes them in the Mandatory Guidelines for Federal Workplace Drug Testing Programs. Oral fluid became an allowed specimen under a final rule in 2023.
Cannabis Mouth Swab Detection Time: How Long THC Stays in Saliva
- THC initial test: 4 ng/mL
- THC confirmatory test: 2 ng/mL
- Specimen volume: 1 mL of oral fluid for the lab
Point-of-collection devices
Roadside kits give a result in minutes. Reported cutoffs for THC range from 4 ng/mL to 50 ng/mL. A higher cutoff cuts false positives from passive smoke and from recent legal use. It also misses low-level use. Devices differ in how they collect fluid. Some use a swab held under the tongue. Some use a pad on a wand.
saliva drug test for cannabis cutoff levels
Detection window
Oral fluid holds parent THC, not the urine metabolite THC-COOH. After smoking, THC shows up within minutes. Most positive results fall in a window of 5 to 24 hours. Heavy daily users can test positive for up to 48 hours. Edibles produce a later and lower peak in oral fluid than smoke. No number predicts a single person. Dose, potency, route and body weight all shift the result.
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What changes the measured level
Smoke in the mouth raises the reading right after use. Residual THC on oral tissue can push a sample over the cutoff in under a minute. Food, drink and mouthwash change pH and volume. Dry mouth reduces the sample. Collection timing matters more than it does for urine.
State limits
States set their own limits and penalties. Some use zero tolerance for THC in oral fluid. Others set limits in blood or oral fluid, from 1 ng/mL to 5 ng/mL. Check the state statute for the exact number and the specimen type. Federal rules do not apply to state prosecution.
Why convenience drives the choice
Oral fluid collection needs no restroom and no same-sex observer. A trained collector gets a sample in a few minutes. The sample is hard to substitute or adulterate. These points explain the shift toward oral fluid in roadside and workplace programs. The trade-off is a short detection window and a cutoff that changes with the device.
Limits
Oral fluid does not measure impairment. A positive result at 4 ng/mL or 10 ng/mL shows exposure, not driving fitness. THC concentration in oral fluid does not track blood THC in a straight line. Labs should confirm every screen by LC-MS/MS before any action.