In direct contrast to other detection methods, blood testing for weed actually detects the psychoactive compound “THC” while it’s in the bloodstream. This is the only effective way to conclusively test for impairment caused by marijuana. Blood testing for marijuana is the preferred way for a court system to test for THC in DUI cases, insurance claims at work or on the road, accidents, or any other situation where sobriety is to be expected.
It’s important to remember that the presence of THC in the bloodstream is not an indicator of inability to drive while under impairment, but instead an indicator of a higher likelihood of mistakes to be made. Users with a significant tolerance may be functionally OK, but that is not taken into account for other substances and shouldn’t be expected for marijuana.
The only thing that truly affects the detection time of cannabis in blood is the frequency of use. For chronic smokers, it’s detectable for up to two weeks in the blood stream, whereas in most it’s simply 2-3 days. Body fat percentage, fluid intake, and other medications play an insignificant role. Furthermore, blood tests are the least susceptible to masking agents that may allow you to pass the screening.
The process involved with blood testing for weed is dependent on the locale. It’s possible for an EMT to draw blood at whatever location desired, be it the side of the road or at a home. Alternatively, most jails are equipped with a medical facility that can be used ensuring a clean drawing. When it comes to samples being collected for legal reasons, there’s a different chain of custody since it is being used as evidence.
If there was an accident in the workplace, an employer may request that all involved head to a clinic to have a blood sample drawn immediately. This is to ensure that when insurance claims are submitted, all personnel involved are cleared of any further accusations. The blood specimens drawn will be collected by the clinic and submitted on behalf of the employer to the lab of their choosing.