The short answer
Cannabis stays on federal drug testing panels. A positive result can end a job offer or start discipline in most states. Federal law gives cannabis users no protection. State law varies. A small number of states limit what employers can do about off-duty use. Safety-sensitive jobs and federal contracts are the main exceptions.
What the test measures
Urine is the most common sample. The lab looks for carboxy-THC, the main THC metabolite. Labs screen at a cutoff of 50 ng/mL. A sample that screens positive goes to a confirmatory test by GC-MS or LC-MS/MS at a cutoff of 15 ng/mL. Labs also test oral fluid, hair, and blood. No test measures current impairment. A THC level does not prove a person was high at work.
Detection windows
- Urine, single use: 1 to 3 days.
- Urine, daily use over months: 7 to 30 days, and longer in some cases.
- Oral fluid: up to 48 hours.
- Hair: up to 90 days.
THC is fat-soluble. Body fat, metabolism, hydration, and dose change the window. Chronic heavy use extends it.
State law
More than 20 states allow adult use. Most of them still let private employers enforce a drug-free policy. A smaller group limits employer action against off-duty use. The list includes California, Nevada, New York, New Jersey, Connecticut, Rhode Island, Montana, and Minnesota. Each has carve-outs for safety-sensitive roles, federal contractors, and jobs regulated by federal law. California's AB 2188 took effect on Jan 1, 2024. It bars most employers from using a positive test for a non-psychoactive metabolite in hiring decisions. It does not cover federal employees or federal contractors.
Federal rules and safety-sensitive work
The Department of Transportation tests truck drivers with a CDL, pilots, rail workers, transit workers, and pipeline workers under 49 CFR Part 40. A state medical cannabis card is not an accepted explanation for a positive result. Federal agencies, federal contractors covered by the Drug-Free Workplace Act of 1988, and security clearance holders face similar rules.
CBD and false positives
CBD does not trigger a THC test by itself. Some products labeled THC-free contain THC. A label error can produce a positive result. Labs confirm every non-negative screen before reporting.
If you use cannabis
- Read the job posting for a drug testing statement.
- Check your state law for off-duty protections and exceptions.
- Ask the employer which panel the lab uses. A four-panel test often omits THC.
- If a result comes back positive, request the confirmation report in writing.
- A Medical Review Officer may call. The MRO reviews prescription drugs. There is no accepted medical explanation for THC under federal rules.
Some states allow a request for accommodation for medical cannabis. Employers can deny the request for safety-sensitive positions. Federal contractors and DOT-regulated employers can deny it in all cases.