How Long Does Marijuana Stay in Your System?

What You’ll Learn in This Article

  • While the active form of THC doesn’t remain in your bloodstream for an extended period of time, THC metabolites can still be found in the body several weeks after use.
  • There are a variety of factors that might affect the amount of time that THC and its metabolites stay in your system.
  • The overall duration and frequency of use by the consumer have a substantial influence on the length of time weed hangs around in the body.
  • A body with higher metabolic functions can break down cannabinoids at a faster rate, shortening the length of time that THC and THC metabolites will remain detectable.

When cannabis is consumed and introduced to the human body, it sparks an exhilarating interaction that leaves a lasting impression in both a literal and figurative sense. After smoking weed, cannabinoids and their byproducts remain detectable in the body, and in many cases remain well after the buzz wears off. 

In order to address the question of how long weed stays in your system, we must first focus our attention on THC, or delta-9-tetrahydrocannabinol, the intoxicating cannabinoid that creates euphoric and stoned effects. Cannabis drug tests often exclusively screen for THC and THC metabolites, which are byproducts that are produced when THC is broken down in the body. 

How Does Cannabis Travel Through the Body?

To fully understand how long weed could stay in your system, it’s important to establish how THC travels through and interacts with the body. 

When cannabis is smoked or vaporized, THC enters the bloodstream through the lungs. From there, THC is carried in the bloodstream directly to the heart and pumped throughout the body, binding 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. 

As blood circulates throughout the body, THC is continuously passed through the liver and broken down into metabolites. To detect the presence of cannabis in the body, most drug screening methods look for one metabolite called 11-nor-9-carboxy-THC, or THC-COOH. 

This inactive metabolite of THC, which is stored in the fat and gradually eliminated through urine and feces, remain in the body for far longer than active THC. That’s why so many marijuana detox drinks and kits claim to eliminate or mask the presence of THC metabolites. 

The process is slightly different when weed enters the system in the form of an edible or capsule. When cannabis is ingested, THC enters the bloodstream through the walls of the stomach and intestine, traveling directly to the liver where a large amount is eliminated or metabolized. The remaining THC and THC metabolites are then circulated by the heart and sent to the brain.   

Key Factors That Influence How Long Weed Stays in Your System 

There are a variety of factors that might impact the amount of time that THC will stay in your system. 

Dosage

The higher the amount of THC that is consumed, the longer it will take the body to break down and work through the THC and its corresponding metabolites. 

Frequency of use

The overall duration and frequency of use by the consumer have a substantial influence on the length of time that weed will stay in your system. Most research on cannabinoid detection demonstrates that THC stays in the system of chronic users for far longer than one time or even occasional users. Frequency of cannabis use is also a notable risk factor in developing cannabis withdrawal symptoms.  

Genetics

Genetics also impacts the length of time that THC remains in the system. For instance, people inherit different variants of the cytochrome P450 superfamily of enzymes, which modify THC in the body resulting in its elimination through the urine.

Fat

The amount of fat in the body is also a significant factor. The metabolite THC-COOH is fat-soluble and binds to fat molecules, where they can be stored for a lengthy period of time. In the same vein, exercise can also impact the levels of detectable THC metabolites. When fat is burned, dormant THC from 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 at a faster rate, shortening the length of time that THC and its metabolites will remain detectable in the body. 

How Long Does Weed Stay in Your System? 

There’s no universal standard for how long weed stays in the system because it depends on too many variables. THC and its metabolites can be detected in blood, urine, saliva, and hair. But existing research allows us to gain a better understanding and make a well-educated estimate.  

How Long Does Weed Stay in Your Blood?

Upon inhalation, active THC can be found in the bloodstream within a matter of seconds and can be detected in plasma for several hours, depending on the frequency of use and dosage. According to a 2004 review, the plasma concentration of THC peaks just 3 to 8 minutes after inhalation and then decreases quickly with a half-life of about 30 minutes. The study claims that THC is detectable in blood for about 5 hours, but the THC metabolite THC-COOH has a detection time of up to 25 days.  

 

In a 2009 study, researchers monitored cannabinoid concentrations in the blood of 25 frequent cannabis users. During seven days of abstinence from cannabis use, 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 of the subjects still had detectable THC concentrations and all subjects had measurable levels of the metabolite THC-COOH. 

So, while the active form of THC doesn’t remain in your bloodstream for an extended period of time, THC metabolites can still be found in the body several weeks after use. 

How Long Does Weed Stay in Your Urine?

Recognized as the preferred method for cannabis drug testing, urine screenings are often used as a benchmark to detect for cannabis use. Most urine drug tests utilize a specific sensitivity for the cutoff concentration of THC-COOH. The most common cutoff concentration point is 50 nanoggrams per milliliter (ng/mL), as suggested by the Substance Abuse and Mental Health Services Administration (SAMSHA).

In a 2005 review authored by Paul Cary, director of the Toxicology and Drug Monitoring Laboratory at the University of Missouri, Cary stated that THC detection times rarely exceeded 30 days, occurring in a select few cases. The study aims to provide “practical cannabinoid detection guidance,” despite the many factors that influence how long weed stays in the system.

 

Using the recommended cutoff concentration point of 50 ng/mL, the study suggests that a chronic cannabis user is unlikely to have detectable THC metabolites in their urine longer than 10 days after the more recent smoking episode. At the lower, more sensitive 20 ng/mL cutoff concentration point, however, the metabolites in chronic users could be detected for up to 21 days after consumption, and possibly longer in some rare instances. For one time users, however, the same study found that even with the most 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 a May 2017 review published in Mayo Clinic Proceedings, weed can be detected in the system for up to three days in occasional users, five to seven days in moderate users, 10 to 15 days in daily users, and more than 30 days for chronic users who consume multiple times a day. 

How Long Does Weed Stay in Your Saliva?

THC and its metabolites can also be detected in the saliva of occasional and chronic users. A 2014 study on cannabinoids in oral fluid found that THC metabolites were detectable in the saliva of occasional users for one to three days and chronic users for up to 29 days.   

How Long Does Weed Stay in Your Hair?

There is mounting evidence that hair follicle drug testing methods are not able to accurately detect marijuana, as some research suggests that the presence of THC and THC metabolites can be transferred to the hair follicles of non-users through contact with hands, sweat, or exhaled smoke. For example, if someone smokes a joint and exhales near someone who doesn’t use cannabis, THC can be transferred to the non-smoker’s head or body hair. A 2015 study found that, after giving participants 50 milligrams of THCA every day for one month, no THC was found in the hair specimen samples, but THC-COOH was still detected. As for the detection period, the hair follicle drug test timeline is much broader than with urine and blood tests, sometimes detecting the presence of THC up to 90 days after use.  

 

On the other hand, a 2017 study that analyzed hair samples collected from 136 subjects found detectable levels of THC in 77% of chronic users, 39% of light users, and zero in non-users, showcasing that the chance of having THC found in hair grows significantly with increased frequency of use. While the authors of the study stated that hair analysis is a viable method for detecting cannabis consumption, they also acknowledge that it’s unreliable for detecting light cannabis use.