From the Guidelines
Marijuana can be detected in urine drug screens for 1–3 days after use, and up to 30 days or more in heavy users. This detection time is based on the metabolite 11-Nor-9-carboxy-THC, which is the primary biomarker used in urine tests for cannabis use 1. The variability in detection time is due to several factors, including the frequency and amount of marijuana use, as well as individual differences in metabolism and body fat percentage.
Key Factors Affecting Detection Time
- Frequency and amount of marijuana use
- Metabolism
- Body fat percentage
- Hydration levels
- Sensitivity of the test being used It is essential to note that urine drug screens can have false positives and false negatives, and providers should be aware of the potential for cross-reaction with unrelated substances in urine 1. Additionally, a negative screen does not necessarily mean that an individual is not using marijuana, as the detection window may have passed or the test may not be sensitive enough to detect the presence of THC.
Clinical Implications
- Providers should verify the detection time for the target substance in the adolescent age group before deploying urine substance use screening 1.
- Confirmation of substances included in the testing panel is crucial, as not all substances are routinely included in panels 1.
- Building ongoing rapport with young people and integrating ECPO screening into annual and interim visits can be an effective avenue to screen for ECPO use in this age group 1.
From the Research
Duration of Urine Drug Screen Positivity for Marijuana
- The duration of urine drug screen positivity for marijuana can vary depending on the extent of use, with 11-nor-9-carboxy-Delta9-tetrahydrocannabinol (THCCOOH) detectable in urine from a few days up to three months after cessation of cannabis use 2.
- Factors such as urine dilution and the time span between specimen collection dates must be considered when interpreting urine drug screening results 2.
- A study found that acute dosing of pure CBD will not result in a positive urine drug test using current federal workplace drug testing guidelines, but CBD products containing Δ9-THC may produce positive urine results for Δ9-THCCOOH 3.
- Another study developed an assay to distinguish marijuana use from tetrahydrocannabinol exposure from contaminated CBD use, using urinary metabolites of tetrahydrocannabinol, 11-nor-carboxy-Δ9-tetrahydrocannabinol, CBD, and 7-carboxy-cannabidiol 4.
- A study on the association of positive drug screening for cannabis with mortality and hospital visits among Veterans Affairs enrollees prescribed opioids found that cannabis use was not associated with increased all-cause mortality at 90 or 180 days, but was associated with an increased hazard of a composite outcome of all-cause emergency department visits, all-cause hospitalization, or all-cause mortality 5.
- Exposure to secondhand cannabis smoke can produce positive urine tests, but positive tests are likely to be rare, limited to the hours immediately post-exposure, and occur only under environmental circumstances where exposure is obvious 6.