Fraser Horton
Fraser Horton
Last Updated on January 30, 2021

Cannabis users have been asking this question over and over as both cannabis use and drug testing have increased around the world. Testing for cannabis consumption has been one of the most common illicit drug tests that employers have used since President Richard Nixon prohibited cannabis as part of the “War on Drugs” campaign.

Recreational marijuana users enjoy the pleasurable body sensations, relaxation, and feelings of euphoria that come from consuming weed and having elevated levels of THC in the body, but they wouldn’t want their pastime to show up on their mandatory drug screening at work.

For that reason, in this article, we’re diving into how long it takes for marijuana to detox from the body, and also for how long it can show on a blood test.

How Is Weed Broken Down in the Body?

In order for weed to produce its psychoactive effects, it first needs to be absorbed in the bloodstream. That means that the two main cannabinoids, tetrahydrocannabinol (THC) and cannabidiol (CBD), are absorbed in the bloodstream and the body metabolizes the cannabis further.

Metabolites can have a different elimination half-life, depending on where they’re stored in the body. For instance, THC metabolites are stored in the fatty tissues and organs for some time. Naturally, the more body fat you have, the longer it will take for your body to detox from them.

After the absorption, THC is broken down in the liver into metabolites, the most important being 11-OH-THC (11-hydroxy-delta-9-tetrahydrocannabinol) and THCCOOH (11-nor-9-carboxy-delta-9-tetrahydrocannabinol), given that they are the ones that will show on a drug test. They remain in our body for a longer amount of time even after the effects of THC and CBD have diminished. 

Drug Tests and Detection Times for Cannabis

Toxicology tests (drug tests) are the tools that measure the presence of metabolites and drug by-products that remain in the body after the effects of the drug have worn off. When it comes to weed testing, tests measure the concentration of THC metabolites (THC-COOH) in the system. The detection methods include:

  • Urine test (Urine drug tests are the most common drug tests done at the workplace and the test is done by checking the urine sample for the presence of THC metabolites); 
  • Blood test (Blood tests are done by taking a blood sample and testing it for the presence of THC metabolites);
  • Saliva test (Oral drug tests help to determine the presence of THC metabolites in the oral fluid);
  • Hair test (The hair follicle test has the biggest detection window when it comes to detecting whether or not someone has been using weed as hair takes the longest time to detox from weed).

How Long Does Weed Stay in the Body?

The detection window that defines how long weed shows up on a drug test depends on many factors. Some drug tests, like the urine drug test, have specific cutoff levels for THC metabolites (for the urinalysis it’s 50 ng/mL), and people who have values above 50 will have a positive result. Cutoff levels are useful since they minimize false positives and optimize drug detection, as sometimes drug tests have resulted in false positives.

Frequency of Use

The most important factor that affects the length of time that weed stays in the body is how often do marijuana users consume weed. Infrequent and light users will be able to detox their body from marijuana much faster compared to heavy and chronic users. 

Amount of THC Consumed

The dosage of THC you’ve consumed will also influence how long your body needs to detox from weed. Lower doses will be metabolized faster, and larger doses will linger longer in the fatty tissues.

BMI and Physical Activity

Since cannabinoids bind to the lipids in the body, they tend to remain in the fat cells of the body for a longer period of time. As a result, people with a lower body mass index (BMI) and a lower metabolic rate will detox much slower compared to physically active people with a higher metabolic rate. Physical activity and an optimal BMI will not only help you maintain better overall health, but will also help you detox from weed faster.

How Long Does Marijuana Stay in the Blood?

Different testing methods can detect marijuana use in different time frames, and the blood test is one of the most common testing methods, apart from urine tests. It’s conducted by testing the provided blood sample for the presence of specific drugs and opiates, including marijuana. 

This type of testing has the smallest detection period, and it depends on the amount of THC consumed and the frequency of cannabis use. Recent use is more likely to get picked up on a blood test.

With this type of test the detection period is fairly short and it can yield positive results from 2 to 24 hours after smoking for infrequent users. Frequent and chronic users can expect a positive result on their blood test for up to a week.

The sensitivity of the test also plays a key role in the detection period. Tests with a higher sensitivity are more likely to detect the presence of THC metabolites in the blood. (Hadland et al, 2016; Verstraete et al, 2004)

Final Thoughts on Marijuana Detection in the Blood

In order to avoid a positive test result, stop marijuana use until your test. And if you’d like to help your body break down (metabolize) marijuana faster, you should maintain proper hydration levels, exercise regularly, and maintain a healthy lifestyle. Some people even decide to try niacin flushes as a way to detox faster. (Gunasekaran et al, 2009)

In any case, marijuana detection through a blood test can have a positive result from 2 to 24 hours after the initial use of cannabis for infrequent users, and even up to a week for heavy users. So make sure you’ve properly detoxed until your scheduled testing date.

Additional Sources

Hadland, S. E., & Levy, S. (2016). Objective Testing: Urine and Other Drug Tests. Child and adolescent psychiatric clinics of North America, 25(3), 549–565. https://doi.org/10.1016/j.chc.2016.02.005

Verstraete A. G. (2004). Detection times of drugs of abuse in blood, urine, and oral fluid. Therapeutic drug monitoring, 26(2), 200–205. https://doi.org/10.1097/00007691-200404000-00020

Gunasekaran, N., Long, L. E., Dawson, B. L., Hansen, G. H., Richardson, D. P., Li, K. M., Arnold, J. C., & McGregor, I. S. (2009). Reintoxication: the release of fat-stored delta(9)-tetrahydrocannabinol (THC) into blood is enhanced by food deprivation or ACTH exposure. British journal of pharmacology, 158(5), 1330–1337. https://doi.org/10.1111/j.1476-5381.2009.00399.x

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