What Does a Positive Cannabis Test Actually Prove?
For healthcare organizations and professionals (B2B) · Physician-led · Updated 2026-07-12 · CLIA #45D2048957 · CAP #8722734
A positive cannabis result is not evidence of impairment. The metabolite outlasts the effect by weeks.CLIA #45D2048957 · CAP #8722734 · Same-day results · Walk-ins welcome
Exposure — not impairment. Urine testing targets THC-COOH, an inactive metabolite of THC that is stored in fat and excreted slowly. In frequent users it can remain detectable for days to weeks after last use, long after any psychoactive effect has ended. There is no urine concentration that establishes impairment at the moment of collection.
What the analyte can and cannot support
| Question | Urine THC-COOH |
|---|---|
| Has this person used cannabis at some point? | Supports yes |
| Was this person impaired at the time of collection? | No — it cannot establish that |
| When did use occur? | Only very roughly; frequency and body composition dominate |
| Recent-use windows | Oral fluid is closer to recent use — oral fluid vs. urine |
Employers and clinicians frequently treat a positive cannabis screen as proof of being high on the job. The analyte does not support that claim, and saying so plainly is part of a laboratory's job.
FAQ
- Can you tell how much someone used?
- No, not reliably from urine. Frequency, body fat and hydration all confound it.
- Does CBD cause a positive?
- Products vary in THC content; contamination is documented. Confirmation identifies what is actually present.
- Which specimen shows recent use?
- Oral fluid has a shorter detection window and is closer to recent use.
- Is this legally defensible?
- Definitive LC-MS/MS with a documented chain of custody is — for exposure. Not for impairment.
References
- SAMHSA — Substance Use Treatment Resources
- NIDA — Cannabis (Marijuana)
- Our CLIA #45D2048957 and CAP #8722734 credentials — verify them yourself
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