How Does Oral Fluid Drug Testing Compare with Urine Testing?

HHS publishes separate Mandatory Guidelines for urine and for oral fluid. The oral fluid guidelines were first published on October 25, 2019 (84 FR 57554) and revised on October 12, 2023 (88 FR 70814). DOT added oral fluid to 49 CFR Part 40 as an alternate methodology in a final rule published May 2, 2023 (88 FR 27596). The employer tells the collector which specimen type to collect (49 CFR 40.14).

Collection steps differ. A urine specimen is provided in private unless the collection is observed or monitored, and the collector checks the temperature within 4 minutes (49 CFR 40.63, 49 CFR 40.65). The urine specimen is at least 45 mL, split into a primary bottle of at least 30 mL and a split bottle of at least 15 mL (49 CFR 40.65, 49 CFR 40.71). For oral fluid, the collector inspects the mouth, waits 10 minutes, and maintains visual contact with the employee during the collection (49 CFR 40.72, 49 CFR 40.73). Each oral fluid bottle holds at least 1 mL of undiluted oral fluid (49 CFR 40.74). Once oral fluid testing is available, Part 40 lists an oral fluid test as an option when a same sex observer cannot be found for a directly observed urine collection (49 CFR 40.67).

Laboratory cutoffs are lower for oral fluid. For marijuana, the urine cutoffs are 50 ng/mL initial and 15 ng/mL confirmatory for THCA, and the oral fluid cutoffs are 4 ng/mL and 2 ng/mL for THC (49 CFR 40.85, 49 CFR 40.91). Urine validity testing includes creatinine, pH, and oxidizing adulterants on each primary specimen (49 CFR 40.87). Oral fluid validity testing is optional. A laboratory may conduct it when a specimen shows abnormal characteristics, and it may include a biomarker such as albumin or IgG (49 CFR 40.92, 49 CFR 40.93).

An employer may use oral fluid testing only when at least two HHS-certified oral fluid laboratories exist. After HHS gives notice of the second laboratory, an 18-month grace period allows employers to continue directly observed urine collections (49 CFR 40.67). The HHS list published September 30, 2026 states that no laboratories are certified to conduct oral fluid drug testing (91 FR 61854).