Workplace Drug Testing: An Employer Compliance Guide
DOT vs non-DOT testing, panels and methods, marijuana state-law conflicts, and how to keep a drug-testing program defensible.
- DOT methods
- Urine + oral fluid (49 CFR Part 40)
- Non-DOT
- Governed by state law
- MRO review
- Recommended for defensibility
Workplace drug testing divides into DOT-regulated testing, which must follow the prescriptive procedures in 49 CFR Part 40, and non-DOT testing, which is governed by a patchwork of state laws that vary widely on what employers may test for and when.
A defensible program starts with a written policy that defines which tests apply to which roles, uses certified laboratories and a Medical Review Officer, and is applied consistently to limit discrimination claims.
State marijuana laws are the fastest-moving variable: a growing number of states restrict adverse action based on off-duty cannabis use or positive THC tests, so policies should be reviewed with counsel. Oral-fluid testing is now an authorized DOT method, expanding options beyond urine.
DOL compliance checklist
- Adopt a written drug-testing policy — Define covered roles, test types, and the consequences of a positive result.
- Separate DOT and non-DOT programs — DOT testing must follow 49 CFR Part 40 exactly — keep it distinct from any non-DOT testing.
- Account for state marijuana laws — Several states protect off-duty cannabis use; align your policy with current state law.
- Use certified labs and an MRO — SAMHSA-certified laboratories and Medical Review Officer review keep results defensible.
- Apply testing consistently — Uniform application across similarly situated employees reduces discrimination risk.
A starting point, not legal advice — verify against the primary sources cited below and current rules for your jurisdiction.