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Cannabis drug testing


Cannabis drug testing describes various drug test methodologies for the use of cannabis in medicine, sport, and law. Cannabis use is highly detectable and can be detected by urinalysis, hair analysis, as well as saliva tests for days or weeks.

Unlike alcohol, for which impairment can be reasonably measured using a breathalyser (and confirmed with a blood alcohol content measurement), valid detection for cannabis is time-consuming, and tests cannot determine an approximate degree of impairment. The lack of suitable tests and agreed-upon intoxication levels is an issue in the legality of cannabis debate, especially regarding intoxicated driving.

The concentrations obtained from such analyses can often be helpful in distinguishing active use from passive exposure, elapsed time since use, and extent or duration of use.

The Duquenois-Levine test is commonly used as a screening test in the field, but it cannot definitively confirm the presence of cannabis, as a large range of substances have been shown to give false positives.

Most cannabinoids are lipophilic (fat soluble) compounds that easily store in fat, thus yielding a long elimination half-life relative to other recreational drugs. The THC molecule, and related compounds, are usually detectable in urine drug tests from 3 days up to 10 days according to Redwood Laboratories; heavy users can produce positive tests for 1-3 months after ceasing cannabis use. The length of time varies greatly according to metabolism, quantity, and frequency of use.


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