The Truth About THC Drug Testing and How Long Cannabis Can Be Detected in the Body

cannabis drug testing


When was the last time you smoked cannabis?

Whether it was an hour ago, yesterday or even last month, the psychoactive cannabinoid known as THC can linger in your system anywhere from a day to 90 days, according to a 2016 study published in the journal, Child and Adolescent Psychiatric Clinics of North America

Like anything you consume, several factors affect THC’s lasting power in the body, including: the potency of cannabis, how quickly your body metabolize it, the amount you consume, and how often.

In the initial inhale of cannabis, the THC quickly travels from the lungs into the bloodstream. Once it’s in the bloodstream, it then passes through the brain and the other organs of the body. This is a quick process; it can take anywhere from 15 to 30 minutes to feel the full effects of smoking cannabis, according to the National Institute on Drug Abuse. 

When ingesting cannabis in the form of edibles like brownies, cookies, candy or tea, the process is a bit slower, and can take anywhere from 30 minutes to an hour to take effect.


How Does Cannabis Appear on a Drug Test?

Drug test work to test the levels of cannabis metabolites, according to a 2012 study. These tests can detect metabolites in the body long after the “high” wears off.

There are a few different methods of conducting a drug test. The most common is using a urine sample, as it is less invasive and the easiest way to complete sample collection. Other methods include saliva, blood, hair, sweat and sometimes even fingernails samples. 

Most of us are aware of the compound’s THC and CBD, but many other cannabinoids make up the cannabis plant. However, drug tests are testing for THC. If the THC has been metabolized by the body, it will appear as the compound, THC-COOH. Since CBD doesn’t have the same psychoactive effect as THC, it will not result in a positive test.


The Most Common Cannabis Drug Testing Methods and Their Effectiveness 


The most effective way to test THC levels in the body is through a urine sample. According to a study published by the National Center for Biotechnology Information (NCBI), many drugs are lipid-soluble, which means that in order for the drugs to exit the body, they must be metabolized. 

This metabolization process starts with the initial intake. Then, the substance almost immediately makes its way through tissues until it reaches the liver, where the body metabolizes it into a water-soluble substance, then excretes it through urine. 

Another reason why urine is the most common way to drug test is that it has a larger window of detection, varying from one day to several weeks after use. 


Saliva and Breath  

According to the aforementioned study by the NCBI, the window of detection for oral fluids is between 24 – 48 hours after consumption. Because of the small detection window, testing oral fluid samples is not effective to analyze patterns of drug use.

The breathalyzer is the most common way to measure blood alcohol levels in the body orally. But it is uncommon to see such technology for cannabis. However, CNN Business reports that as of January of 2020, several tech start-ups and university scientists are close to commercializing a version of a cannabis breathalyzer.

However, as of now, January 2021, only one company —  Hound Labs — seems to be close to bringing a breathalyzer to market. They’re still in the early stages of getting the breathalyzer out to eligible organizations, as there’s a waiting list. 



Cannabis enters the bloodstream seconds after inhalation. The THC then quickly passes through the body, and the body metabolizes it. The bloodstream may reabsorb some of the THC after metabolization. The body stores these metabolites, THC-COOH, in body fat. They then exit through the waste system.

Similar to oral fluid testing, blood testing also has a short detection window. Because cannabinoids pass quickly through the bloodstream, blood tests are rarely used. Instances in which officials may use blood testing include roadside testing or after automobile accidents. 



The hair test is the second most common way to test one for cannabis consumption, due to the large detection window and ease of sample collection. But this method is controversial due to the ability to trigger a false positive, proving itself to not be as reliable as a urine test. 

Despite this, hair samples remain a popular form of drug testing because they detect THC in hair as far back as 90 days after use, depending on how quickly the body metabolizes it. 

One may complete a drug test for several reasons. There are pros and cons to each method. Ultimately, however, drug tests all serve the same purpose — to detect recent THC.


Emerald contributor since October 2020


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