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Will alchohol blood test show weed?

Twenty-three states and the District of Columbia currently have laws legalizing marijuana in some form, and other states have decriminalized the possession of small amounts of marijuana. The remaining states continue to debate the merits of updating marijuana laws.

With increased use of the drug, it’s not surprising that there are more users concerned with how the drug will impact their ability to drive and whether or not a blood test will detect marijuana use.

Blood tests and marijuana use

Tetrahydrocannabinol (THC), an active ingredient in marijuana, can be detected through a blood test. Detection times can vary from 12-24 hours. Effectiveness for detection and the variation of detection times depends on several factors: the type of marijuana ingested, the frequency of use, the dosage, the genetic makeup of the smoker, metabolic factors, and digestion.

Marijuana testing and DUI

States which have legalized recreational marijuana use and those allowing its use for medicinal purposes have laws which discourage its use while operating a motorized vehicle.

In fact, states such as Colorado, which has legalized its recreational use in the last several years, have established a blood level limit for active THC (which is supposed to provide objective information about when a driver is too impaired to drive). Although marijuana can be detected through four different tests (blood, urine, hair, and saliva), blood tests are most frequently administered by law enforcement because of their ability to detect active Delta 9- THC.

Currently, the limit for Delta-9 Tetrahydrocannabinol (THC) is 5 nanograms per milliliter of blood. Drivers arrested with a blood concentration level at that level can be charged with a Colorado DUI.

Drivers in other states have also given their implied consent to submit to a blood test for alcohol or drug detection if they are arrested for driving under the influence (DUI).

What should you know about marijuana blood testing?

Given the societal acceptance of smoking weed and its increased use, many states have only now begun to really address the issue of detecting the presence of cannabis in the body and what levels may lead to impairment when operating a motorized vehicle.

Blood testing for marijuana, however, remains a controversial issue for determining whether someone is actually too impaired to drive. For example, disagreements remain about whether the established legal limit in Colorado is fair, although studies indicate that this threshold has generally proven to decrease reaction times and depth perception.

Other parties are concerned about the method and process of testing. Questions which have not fully been addressed include the need for standardized testing times, which are critical for detecting psychoactive THC, and the fact that marijuana takes longer to dissipate in habitual users.

Opponents of the current blood testing practices argue that if a blood test is done hours after marijuana use the test is detecting remaining metabolites (THC-COOH), which are not valid indicator of impairment, rather than psychoactive THC.

There is also concern that habitual users could be charged with driving under the influence of marijuana simply because the dissipation times are longer, not because they are actually impaired.

Bottom Line:

While law enforcement and state officials are working to develop strategies and tests for marijuana detection and hope to find the best methods for determining impairment, it could take a few years for the legal standards to be implemented.

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