How long does weed stay in your system?

When we consume cannabis, its cannabinoids and other byproducts remain detectable in our bodies well after the buzz wears off. 

Learn how the body processes THC and why genetics, fat, and metabolism can affect how long weed stays in your system.

How does the body process THC?

The body processes THC (delta-9-tetrahydrocannabinol), the intoxicating cannabinoid known for creating euphoric, stoned effects in several ways, and is dependent on the method of consumption.

Inhalation 

When inhaled with a vaporizer, joint, or bong, THC enters the bloodstream via the lungs and is pumped throughout the body, where it binds to the CB1 receptors located in the brain, certain organs, and central nervous system, as well as the CB2 receptors in the spleen and immune system, gastrointestinal tract and other organs and tissues. These receptors are part of the endocannabinoid system. It will only take a few minutes to notice its effects. 

Ingestion

With edibles or tinctures, THC will enter the bloodstream through the walls of the stomach and intestines, traveling directly to the liver. The liver breaks down much of the THC to a cousin compound called 11-hydroxy-THC, which also enters the bloodstream. THC and 11-hydroxy-THC are detectable in the bloodstream after cannabis is ingested through the digestive tract. 

This process usually takes 30 - 90 minutes to feel effects and varies widely depending on your tolerance and metabolism. 

How long does THC stay in your system?

The most common belief is that weed will stay in your system for only 30 days. However, the amount of time THC will actually stick around depends on many factors that are unique to your individual body and consumption habits:

  • Dosage: The larger the amount of THC consumed, the longer it will take the body to break down and work through it and its corresponding metabolites. 
  • Frequency of use: Most research on cannabinoid detection demonstrates that THC stays in the system of chronic consumers far longer than one-time or even occasional consumers. Long-term, high-frequency cannabis use is a notable risk factor for developing Cannabinoid Hyperemesis Syndrome.  
  • Genetics: People inherit different variants of the cytochrome P450 superfamily of enzymes, which modifies how well and quickly THC is broken down. This ultimately affects the duration of effects and how quickly THC and its metabolites will be excreted.
  • Fat: When burned, dormant THC stored in fat can be released into the blood and excreted from the body in urine or feces.
  • Metabolism: A body with higher metabolic functions can break down cannabinoids faster, shortening the time that THC and its metabolites will remain detectable in the body. 

What do drug tests look for?

As blood circulates throughout the body, THC is continuously passed through the liver and broken down into numerous metabolites. The most commonly screened for metabolite is called 11-nor-9-carboxy-THC or THC-COOH

medical cannabis Photo by: Gina Coleman/Weedmaps

This inactive metabolite is stored in body fat and gradually eliminated or metabolized. It remains in the body far longer than active THC, which is why so many cannabis detox drinks and kits claim to eliminate or mask the presence of THC metabolites.

How long is weed detectable on a drug test?

How long weed — or the presence of THC metabolites — is detectable depends on the type of drug test administered. It's also affected by your unique physical functions and frequency of consumption.

Types of weed drug tests

THC is most commonly screened through the blood, urine, saliva, and hair.

Blood

Blood tests can detect THC metabolites for several days to a few weeks. Upon inhalation, active THC can be found in the bloodstream within seconds and detected in plasma for several hours, depending on the frequency of use and dosage. 

In a 2004 review published in Therapeutic Drug Monitoring, the plasma concentration of THC peaks just three to eight minutes after inhalation and then decreases quickly with a half-life of about 30 minutes. 

In a 2009 study published in Addiction, researchers monitored cannabinoid concentrations in the blood of 25 frequent cannabis consumers. During seven days of abstinence from cannabis, nine subjects, or 36%, had no measurable THC in their system, while the other 16 still had at least one positive THC test over the same timeframe. After the weeklong period ended, six subjects still had detectable THC concentrations, and all subjects had measurable levels of the metabolite THC-COOH. 

Urine

Urine tests usually detect THC metabolites for 1 - 30 days after partaking. Most urine tests use a specific sensitivity for the cutoff concentration of THC-COOH — 50 nanograms per milliliter (ng/mL), as the Substance Abuse and Mental Health Services Administration (SAMHSA) suggests. 

A 2005 National Drug Court Institute review states that THC detection times rarely exceed 30 days and that a chronic cannabis consumer is unlikely to have detectable THC metabolites in their urine longer than ten days after their most recent smoking session. However, at the lower, more sensitive 20 ng/mL cutoff concentration point, the metabolites in chronic consumers could be detected for up to 21 days after consumption and possibly longer in some (albeit rare) instances. For one-time consumers, the same study found that even with the more stringent 20 ng/mL cutoff concentration point, it would be unlikely for a drug screening to detect THC metabolites in urine after seven days.

According to the Mayo Clinic, weed can be detected in urine for up to three days in occasional consumers, five to seven days in moderate consumers, 10 to 15 days in daily consumers, and more than 30 days for chronic consumers. 

Saliva

THC metabolites can be detected in saliva for one to three days after occasional consumption or a month if you consume regularly. 

A 2014 study published in Drug Testing and Analysis looked at cannabinoids in oral fluid and found that THC metabolites were detectable in the saliva of light consumers for one to three days and frequent consumers for up to 29 days.

Hair

Hair tests can detect THC metabolites for as long as 90 days and increase with frequency of consumption. 

A 2017 study published in Drug and Alcohol Review analyzed hair samples collected from 136 subjects and found detectable levels of THC in 77% of chronic consumers and 39% of light consumers. However, there's mounting evidence that hair follicle drug testing cannot detect cannabis accurately. 

Research published in Scientific Reports suggests that THC and THC metabolites can transfer to the hair follicles of non-consumers through contact with hands, sweat, or exhaled smoke. For example, if someone smokes a joint and exhales near someone who doesn't consume cannabis, THC can be transferred to the non-smoker's head or body hair and be detected on a drug test. 

FAQ

Will one hit of weed make you fail a urine test?

It's possible if a test is particularly sensitive and the weed is high in THC. However, the odds of getting a positive test after just one hit are much lower if you never consume weed than smokers who consume every day. 

How long does weed stay in your bloodstream?

Active THC only stays in your blood for a few hours. However, blood tests can detect THC metabolites for a few days to a few weeks, depending on how much you consume. 

How long does weed stay in your urine?

Urine tests can detect THC metabolites 1 - 30 days after partaking, depending on metabolism and consumption frequency.

How long does weed stay in your saliva?

Saliva tests can detect THC metabolites for one to three days after consumption or a month if you consume regularly. 

How long does weed stay in your hair?

Hair tests can detect THC metabolites for as long as 90 days; however, these tests can be inaccurate or misleading when detecting recent cannabis consumption in light consumers. 

Does CBD show up on a drug test?

Currently, there are no drug tests for CBD or its metabolites. Since most CBD products, even isolates, contain some THC, there is a risk of testing positive for THC metabolites, especially with regular use.


This article has been reviewed by Bonni Goldstein, MD, a physician specializing in cannabis medicine in Los Angeles, California, owner and medical director of CannaCenters, and medical advisor to Weedmaps.com.

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The information contained in this site is provided for informational purposes only, and should not be construed as medical or legal advice. This page was last updated on October 13, 2023.