May 30, 2024

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Cannabis Impairment Detection: Ways to Keep You Safe

3 min read

In states where recreational cannabis is legal, driving under the influence of the drug remains a danger for consumers. Knowing your limits and taking precautions is essential to ensure you get home safely after enjoying a joint or edible. Impairment detection is extremely important, especially when you consider that drivers who test positive for THC are routinely involved in accidents. As more states legalize recreational marijuana, more research on the effects of the drug on driving ability has been conducted. The results have been concerning, with studies showing that drivers under the influence of cannabis are significantly more likely to be involved in a car crash than sober drivers. In fact, those who drive after using cannabis are almost twice as likely to be in a car accident than those who don’t use it at all–even if they aren’t impaired at the time of the test.

Cannabis Breathalyzers

If cannabis impairment detection involves a blood test, why don’t law enforcement officers administer one of those? Well, they could, but they don’t because blood testing isn’t 100% reliable and doesn’t show whether a person was high at a particular moment in time. Blood tests for cannabis show only one thing: The level of THC in your system. The presence of THC in your blood indicates only that you’ve used cannabis at some time in the past few weeks or months. It does not show whether you are or are not impaired at the time of the test. Police officers also can’t administer a breathalyzer test for cannabis impairment because THC is not water soluble, meaning it can’t be measured in breath the way alcohol is.

Marijuana Blood Tests

Blood tests are generally considered the most accurate way to determine whether someone has used cannabis. While they are a more involved procedure than a saliva test, they are also more reliable. Blood tests can detect THC in your system for up to a month after use. The significant amount of time that cannabis remains in your blood stream makes it a less reliable indicator of current impairment. Like blood alcohol tests, blood tests for cannabis can be used to charge someone with a DUI, even if they aren’t currently impaired.

Marijuana Saliva Swabs

Saliva swabs are a less invasive way to test for cannabis impairment. They test for the presence of THC in the mouth, not in the bloodstream. Unlike blood tests, which can be administered by police officers, saliva tests are used in the workplace to detect cannabis impairment. Saliva tests are less accurate than blood tests, but they are more convenient, cheaper, and can be used in real time without a person having to go to a lab for the test. While it is possible to detect THC in saliva after as little as one hour of use, the presence of the drug in your mouth is not an indicator of current impairment.


Impairment detection is important because a driver under the influence of the drug poses a danger to themselves and others on the road. Roadside testing for cannabis impairment is not as accurate as other alcohol breathalyzer tests, so it’s important to know your limits and take precautions to ensure you get home safely after enjoying a joint or edible.