When you get a drug screening, you probably assume that it will look for the presence of THC. However, modern drug tests look for a metabolite called “TCH-COOH”. Also known as “carboxy-THC,” this metabolite is created after consuming cannabis. Unfortunately, the ability to detect this metabolite has made drug screenings more difficult.
How Does Detection Work?
With most drugs, the presence of the actual drug is what tests look for. However, actual THC leaves your blood quickly, making a test that scans for just THC nearly useless. After you use cannabis, it’s stored in your fat cells, since it’s only soluble in fat.
Urine and blood tests look for this “carboxy-THC,” rather than “hydroxy-THC,” the metabolite produced first and eliminated within hours. TCH-COOH is used to see if someone uses cannabis regularly. According to a National Institutes of Health study, between 60% and 100% of people who regularly use cannabis will still have this metabolite detected 28 days after they have stopped using it.
Does This Affect Roadside Sobriety Tests?
Technically, there are two different tests officers can administer. The “hydroxy-THC” test is fairly accurate at judging whether you are impaired due to cannabis. Many states that have legalized medical or recreational cannabis take this approach. However, the “carboxy-THC” test is cheaper, and most states where cannabis isn’t legal use this at DUI checkpoints.
You could have gone for more than a month without consuming cannabis, but if you’re administered a “carboxy-THC” test, you could show positive. Officers less educated in drug screening may take this as evidence that you’re driving under the influence and place you under arrest.
Will CBD Supplements Trigger a False Positive?
CBD in itself doesn’t create THC metabolites. However, there is a chance that you could fail a drug test even if you only used CBD. The chances of this increase if you either have marijuana-derived CBD from a dispensary or you use a “full-spectrum extract,” even if it’s from hemp.
How Long Should I Wait Before the Screening?
Unfortunately, there’s no calculator that can tell you when your TCH-COOH levels will be low enough to not trigger a positive reading. However, the study showing a detection rate of 60-100% 28 days after last use was of people who used cannabis regularly for years.
A Mayo Clinic Study in 2017 sought to answer this question. It determined that, on average, cannabis can be detected for around three days after use for those who only use it occasionally. Those using a few times a week were detectable between five and seven days. Those who had cannabis daily, but not 24/7, were detected between ten and fifteen days. Only chronic cannabis users who took it 24/7 were subjected to a detection window of more than thirty days.
Remember that there’s no magic bullet for drug screenings. Cannabis testing will likely continue to fade away as the years go on, but in the meantime, sticking to these guidelines should be enough for most people.