The results from a clean saliva drug test are available within 24 hours, according to LabCorp, a provider of saliva drug tests. For tests that require further evaluation, it takes up to 72 hours for the results.
Saliva drug tests are performed by placing a swab under the tongue to collect saliva from the test subject. Forensic Fluids, a drug testing laboratory, reports that a saliva test can detect drug use immediately, whereas a urine test only detects drug use that occurred more than four hours prior to the test. It is also more difficult to cheat on a saliva test, and the process is less invasive.