How Long Does it Take for Weed to Leave Your System? Tests & Timeline

how long does weed stay in the system

Whenever a person smokes or ingests weed, all those hundreds of plant compounds interact with our bodies through our cannabinoid receptors. The reactions it can yield are why humans have used cannabis for a variety of purposes for hundreds of years. That means drug addiction has been an affliction that’s been plaguing society for much longer than you’d think.

The interaction of weed compounds with the human body also explains why cannabinoids and their byproducts remain detectable in the body for quite some time, even after the buzz wears off. This begs the question, “how long exactly does weed stay in the human body?” Let’s first explore how our bodies process those plant compounds.

What Is THC, and How Does Your Body Process It?

Tetrahydrocannabinol, also known as THC, is the primary psychoactive compound in cannabis. It’s also the one that produces the sensation of being high. Once ingested, THC is absorbed into various body tissues and organs, including the brain, the heart, and even fatty tissues. The liver also metabolizes it into 11-hydroxy-THC and carboxy-THC (metabolites). After being processed by the liver, those metabolites are then quickly excreted in the urine.

The other THC particles that were absorbed by the organs and tissues are released back into the bloodstream after a certain time has passed. The liver will then process those and turn them into metabolites.

how long does weed stay in your system
How Long Does Weed Last in Your System

That cycle of absorption and excretion is what normally happens to cannabis when ingested in normal amounts. Those who use cannabis regularly, though, may experience THC building up so quickly in their fatty tissues that their bodies just can’t keep up eliminating it in time. This is the reason why heavy smokers of marijuana can still test positive for THC even after a couple of days or even weeks have passed since their last use.

Different Types of Drug Tests

There are several different sampling types being used today to detect traces of THC and cannabis in the human body. However, the timeframe for detecting the presence of marijuana varies significantly between the tests.

Urine Testing

The urine test is the most common form of drug and alcohol testing used by many laboratories and institutions. It is the least invasive and most legally acceptable form of employment drug testing being used today.

The most common urine analysis used is set to detect 50 nanograms of THC per milliliter of urine. This means that you can easily overcome the test by flushing your system for the day with a detox kit. It’s very much possible to have diluted results, which means you need to retake it because the test was inconclusive.

Saliva-Based Testing

Saliva testing is more commonly used for recent drug use and can be easily performed to produce faster results. The test is conducted by collecting saliva through the swabbing of the inner cheek or by having the subject spit into a cup. It’s the least expensive testing method used today and can detect cocaine, amphetamine, and methamphetamine use within the past few days. Marijuana, however, can only detect traces for up to 10 hours after use.

Hair Follicle Testing

The hair test is regarded by many as the best indicator of repeated drug use since it has the ability to detect traces of drug use up to a 90-day window. Those that are immediately suspected of drug addiction are subjected to hair tests because of its wider detection window. The test can even be used to determine when the drug was used, how long it was used for, and when the use was discontinued.

Despite the ability to test further back than a urine test, hair tests are not the best choice for identifying recent cannabis use. This is because it takes some time for the THC to show up in your hair. 

Perspiration Testing

This is a new type of drug testing primarily used to monitor addiction recovery or people on probation. Perspiration drug testing works through a sweat patch affixed to the skin for a period of 14 days. The patch is worn by the subject to detect the presence of drugs excreted through sweat. 

Blood Testing

This is the most expensive and invasive form of drug testing but also happens to be the most accurate. Only trained phlebotomists can perform this method, and the sample must be sent to a lab for analysis.

Blood tests actually detect the presence of the substance and its metabolites right at the time of testing. Within seconds after you smoke weed, traces of THC will start showing up in your blood. The substance can be detected for 1 to 7 days in the blood of light users and up to 2 months for heavy users.

How Long Does Marijuana Stay in Your System?

The short answer is it depends on a lot of factors. The effects of marijuana fade rather quickly, but the drug and its chemical compounds can be detected for quite some time. Even the methods of detection tell different stories as the THC concentrations vary on different parts of the body.


Cannabinoids are lipid-soluble compounds, meaning they bind easily to fat molecules in your body, making it harder to excrete through your urine. Cannabis compounds are detectable in urine depending on the amount and frequency of usage:

  • Occasional users (three times a week): 3 days
  • Moderate users (four times a week): 5 to 7 days
  • Chronic users (daily): 10 to 15 days
  • Chronic heavy users (multiple times a day): more than 30 days


THC can be detected in the blood for 1 to 2 days. However, through heavy and frequent use, the length of time that cannabinoids can be detected increases. As mentioned above, weed is released into the bloodstream after inhalation and is then absorbed by fatty tissues. However, the metabolites processed by the body may remain in the bloodstream for days.


The smoke produced by weed joints is full of THC molecules that easily contaminate a person’s oral cavity, and it leaves a trail for several hours. While the level of consumption isn’t much of a factor when conducting a saliva test, cannabinoids in the mouth can only be detected within 4 to 6 hours after the last joint smoked.


Whenever THC is ingested, the cannabinoids reach the hair follicles via tiny blood vessels. However, it can take some time before those traces of THC can be detected. This is due to the rate at which hair grows out of your head. A 1.5-inch hair segment taken close to the scalp can provide a window of weed use for the past three months.


Cannabinoid compounds can stay in your system for quite some time, depending on the level of consumption. The length of which it can remain in your system, and the detection window are two different factors to consider when trying to answer the question, “how long the drugs stay in your body?” It pays to understand how these things work to give you an idea of how possible it is to get a positive result in a drug test. Regardless of how long cannabis stays in your system, it is still a formidable drug that could lead to misuse, abuse, and eventually drug addiction.