First question: is your job DOT-covered?
The U.S. Department of Transportation (DOT) testing program covers designated transportation roles and agencies. It is not a universal rulebook for every workplace. Start by checking whether your position is subject to 49 CFR Part 40 or an agency-specific rule. Do not infer coverage from a job title alone.
What DOT says about a cannabis-positive result
DOT's May 2026 Office of Drug and Alcohol Policy and Compliance Q&A says a medical cannabis card, physician recommendation, or dispensary record does not make a confirmed marijuana-positive test negative under Part 40. The Q&A also says marijuana use is incompatible with safety-sensitive functions. This is a DOT-specific rule statement, not a conclusion about every non-DOT employer.
What NIOSH says about workplace evidence
CDC's National Institute for Occupational Safety and Health (NIOSH) says THC levels detected in positive urine or blood tests do not permit sound inferences about frequency of use, exact time of last use, or cannabis-related impairment. NIOSH treats cannabis-at-work policy and impairment measurement as research areas that need further work. A test result and a fitness-for-duty decision are not interchangeable.
What depends on employer and state
For a non-DOT role, read the current written policy, any collective agreement, and the applicable state law. This page does not determine accommodation, discipline, or privacy rights. For a related cross-border policy example, see Canada workplace testing; rules there do not govern U.S. employment.
Quick FAQ
Does a state medical cannabis card excuse a DOT positive test?
DOT's May 2026 guidance says no; a state card or dispensary record does not qualify as a legitimate medical explanation under Part 40.
Do DOT rules apply to every job?
No. DOT rules apply to covered transportation roles and programs; this page does not determine whether a specific position is covered.
Can a test result alone show current impairment?
NIOSH says THC levels detected in positive urine or blood tests do not permit sound inferences about frequency of use, exact time of last use, or cannabis-related impairment.
Sources
- DOT Part 40 §40.137 Q&A -- directly read 2026-09-25; current May 2026 interpretation.
- CDC/NIOSH: Cannabis and Work -- directly read 2026-09-25; testing inference limitations and research boundary.
This page does not decide an individual worker's coverage or employment rights.