Medically Reviewed by
Jason Crawford

Article Last Updated on January 5, 2023

It’s a fact that both cannabis use and drug testing have increased all over the world in the past decade as a result of increasing legalization laws and the expanding cannabis market. For marijuana users, cannabis consumption is either recreational or medicinal, depending on their personal needs.

However, a typical question that all cannabis users ask regardless of why they consume weed is related to the excretion of cannabis metabolites from the body. Mainly they wonder which tests are used to check for drug use and how long it takes for weed to get metabolized from the body after their last use.

Exactly that subject will be the main focus of this article. We’ll discuss the most common cannabis drug screenings, and answer the pressing question “Can weed be detected in blood tests.”

How the Body Metabolizes THC and CBD After Cannabis Consumption 

Following the consumption of cannabis through inhalation, ingestion, or topical application, the cannabinoids in weed are absorbed in the bloodstream. From there, cannabinoids such as tetrahydrocannabinol (THC) and cannabidiol (CBD) produce their psychoactive, sedative, anti-inflammatory, and sedative effects on users. When the effects of weed start decreasing, it’s a sign that the body has started metabolizing the cannabinoids.

The body metabolizes the cannabis through the liver, and breaks the cannabinoids down into metabolites. Depending on where the cannabis metabolites are stored in the body, they have a different elimination half-life. 

When the body metabolizes THC into its metabolites 11-OH-THC (11-hydroxy-delta-9-tetrahydrocannabinol) and THCCOOH (11-nor-9-carboxy-delta-9-tetrahydrocannabinol), the metabolites are generally stored in the fatty tissues, where they remain even after the effects of the cannabinoids have diminished.

The metabolites don’t cause impairment, but they can be detected through various drug tests for an extended amount of time. Whether or not you get a positive test result will depend on the drug test you use, how much cannabis you’ve consumed, and how long has passed between the last time you used cannabis and the day of the test. 

Common Cannabis Drug Tests and Their Detection Times

Drug tests, otherwise called toxicology screens, are used to measure the presence of cannabinoids and their metabolite by-products after drug consumption. Cannabis drug tests generally check for the presence of THC and THC metabolites through:

  • Urine tests (the most common workplace drug tests which check the urine sample for the presence of THC metabolites); 
  • Blood tests (apart from urine tests, blood tests are the most commonly used drug tests that check for presence of THC metabolites);
  • Saliva tests (oral drug tests check the oral fluid for the presence of THC metabolites);
  • Hair tests (hair follicle tests have the biggest detection window out of all drug tests).

What Affects How Long Weed Stays in the Blood?

According to the FDA, the cutoff THC levels are 50 nanograms per ml, which means that results over 50 ng/ml are considered a positive result. Cutoff levels minimize false positive tests, and give an exact frame for detection. (Kulig et al, 2017)

The detection window of cannabis depends on the following factors:

  • Cannabis frequency of use. What mostly affects how long weed stays in the body is the frequency in which users consume marijuana. Generally, chronic users will need a longer time to detox from weed compared to occasional users.
  • Amount of THC consumed by marijuana users. How much cannabis you consume will directly influence how long it remains in your body. Larger doses remain in the fatty tissues for a longer period compared to lower doses.
  • BMI and physical activity of marijuana users. As we’ve previously mentioned, cannabinoids and cannabis metabolites bind to the lipids in the body, therefore physical activity and an optimal BMI will also help you detox from weed faster.

How Long Does Marijuana Stay in the Blood?

We’ve determined that weed can be detected through the blood, but compared to other tests, the blood test has the smallest detection period. Blood tests detect marijuana use through testing the blood sample and comparing it to the cutoff levels for marijuana. These tests are mostly used to check for recent use of cannabis. 

The length of time that weed is detected in the blood is as follows:

  • Occasional users will get a positive result from 2 to 24 hours after cannabis consumption;
  • Chronic users will get a positive result for about a week.

Finally, whether you get a positive or negative result will also depend on the sensitivity of the test, since tests with a higher sensitivity can detect the presence of THC metabolites for longer. (Hadland et al, 2016; Verstraete et al, 2004)

New Drug Tests Appearing on the Cannabis Market

As the cannabis market expands, new drug tests may become a gold standard in the future. One of them is the breathalyzer which is similar to the breathalyzer for alcohol and aims to detect whether a driver is operating a vehicle under the influence of cannabis

This device can detect the presence of weed on the spot, which is why a lot of companies are researching the technology in order to provide tests which will give police officers an upper hand when pulling over-intoxicated and drugged drivers. 

If you’ve been consuming cannabis and you’re driving, it’s best to wait for the effects of weed to pass before you drive back home. Getting a cab, or having a sober friend drive you home is also a good idea.

Conclusion on Marijuana Detection in the Blood

Getting a clean drug test is important to cannabis users, especially if it’s a mandatory drug test at work. However, you may help your body break down cannabis in time for your workplace drug testing if you quit cannabis prior to the test, exercise (just not on the day of the test), eat a healthy diet, and hydrate adequately. Some users even try out different detox drinks and niacin flushes, although they aren’t guaranteed to work for everyone (Gunasekaran et al, 2009). Also, we’re not recommending cheating on drug tests as this is against the law.

To sum up, cannabis detection is possible through a blood test, and users can expect to get a positive result up to 24 hours after initial use if they’re consuming cannabis occasionally, and up to a week if they’re chronic users. 

If you have a drug test in the near future, try to give your body proper nutrition and enough hydration to pass it with flying colors. And for any medical advice you may have, don’t hesitate to contact your healthcare provider.

Additional Sources

Kulig K. (2017). Interpretation of Workplace Tests for Cannabinoids. Journal of medical toxicology : official journal of the American College of Medical Toxicology, 13(1), 106–110. https://doi.org/10.1007/s13181-016-0587-z

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

A passionate advocate for the benefits of cannabis. Fraser Horton, who has a background in botany and a strong love of nature, has spent years researching how cannabis affects the body and mind. He established Leaf Nation in 2020, where he has devoted himself to educating people about the legalisation of marijuana and its safe and responsible use. Fraser is committed to highlighting cannabis’ potential for improving wellness and working to dispel the stigma associated with its use.


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