Determining how long weed or its chemical compounds will remain in the system is a common question for users and testers alike.
To answer this question, you need to understand how the compounds are detected and what factors can affect detection. The type of testing can also have an impact on how long levels can be identified in the body. The following guide taken from the blog of 420Evaluations will show you how THC is detected and what length of time it is likely to be found through current testing methods.
 may be looking for the psychoactive or non-psychoactive form of THC. Since the non-psychoactive form of the compound can stay in the body much longer than the effects of the drug are felt, this means that some drug tests can detect trace amounts long after use. The basic types of drug tests in order of popularity of use include
• Urine testing
• Blood-based testing
• Hair sampling
• Saliva collection
According to the University of Rochester Medical Center , urine testing is the most common form of testing for THC, and it focuses on detecting the non-psychoactive components known as metabolites. This form of testing can detect use for several days or weeks. Blood-based testing used to be the most common version, but it has fallen out of use because urine tests are cheaper and less intrusive. Blood-based testing looks for the psychoactive form of THC and is able to detect compounds for a much shorter timeframe than urine testing. Hair sampling and saliva collection are more recent versions of drug testing. Hair sample testing looks for non-psychoactive residues and can detect THC months after use. Saliva testing is not widely accepted and as their results have not proved reliable.
 or CDC indicates factors like individual metabolic rate, chronic versus light use, metabolite quantity present, diet or exercise, and age can all impact the levels of THC and how long the metabolites are able to be identified through laboratory testing. Individual biological variations may also be a factor, with some people processing THC and related chemicals at a much faster or slower rate than others. Heavier weight or body mass may also be a factor that affects the length of time levels are able to be identified in tests because THC tends to be stored in the body’s fatty tissues.
Other factors that affect levels are caused by differences in the level of use, type of ingestion, and quality of the drug. According to the American University  in Washington D.C., the amount of pot, method of use, frequency of use, and concentration of certain chemicals like THC in the plant used can all have a significant effect on the amount of time it takes for THC to be broken down in the body. With a higher quality specimen or daily use, the amount of THC in the body is higher, and the levels will be able to be detected for a much longer period of time. In many instances, a single use of pot will not be enough to remain detectable for very long.
, also known as DAST or drug abuse screening tests, detects THC metabolites that may be present in the urine. Urine testing is not only the most popular testing methods, but it can also detect levels of THC for much longer than blood-based testing. As the chemical compounds from pot enter the body, they pass first into the bloodstream and later into fatty tissues. The breakdown of the compounds is released through the urine and feces after that. This timeline means that a urine test is unlikely to detect metabolites immediately after use, while the user is impaired. This form of testing does allow for detection beginning a couple of hours after use and can continue to detect THC metabolites for days or weeks, depending on the type of use and concentration of THC in the product.
According to the CDC  the smoke from a single pot cigarette can produce enough of the THC metabolites to be detectable in urine for several days after use. Very little can be done to speed up the process through which the body metabolizes THC and related chemical compounds. The CDC also indicates that, for heavy users, the detectable amounts in their body may be present for several days to several weeks after use stops. Research even indicates that, for certain high-use individuals, THC metabolites may be present and identifiable by a urine test for over 100 days after use has stopped. This can vary considerably based on the amount of use, quality of product, length of use, and other factors. In some instances, it is also possible for a regular user to pass a urine test as soon as one to two weeks after their last use.
 plasma concentrations peak within a few minutes and generally fall within the first six hours. Still, detectable amounts may be present for considerably longer.
Blood-based testing is generally able to detect THC from a single use for somewhere between 12-24 hours and may detect regular use for several days or longer than a week after stopping. The type of blood-based testing being used can make a difference in how long detectable levels of THC are identifiable. The CDC recommends plasma testing, but other testing methods may be used. These methods are less effective. Concentrations found from a whole sample may be up to half as high as those found in a plasma or serum test. In recent testing  the majority of heavy users that were tested for THC using blood-based testing were no longer testing positive after seven days, although some did still test positive after that interval.
>How Long Does Edible Weed Stay in Your System?
Edibles are becoming a more popular way to use pot, and their use can have an effect on drug testing.
Edibles are consumed, allowing THC to enter the body in a different way than smoked or vaporized pot. Edibles take longer to enter the bloodstream, making it take longer before detectable amounts can be found through blood-based testing. They also metabolize at a different rate than more traditional smoked doses. Once in the bloodstream, edibles can maintain detectable levels in blood-based testing for longer than smoking does, with some users being detectable for four to six days after a single edible dose. With urine testing, the amount of time an edible stays detectable is similar or slightly shorter to that of smoking pot.
How Long Does Weed Stay in Your System Chart?
A large amount of research on THC testing has been conducted by the government, educational institutes, and private individuals.A number of individual factors may cause a wide variation in the length of time that levels are detected. The following chart provides a synopsis of how long THC levels may be detectable in various testing methods.
Urine Testing Blood-Based Testing Hair Testing
Smoked – single use 1-7 days 6-24 hours May not detect
Smoked – daily use 7-100+ days 2-7 days 3+ months
Edible 7-100+ days 2-7 days May not detect to 3+ months
Please note that these time frames are estimates based on various reporting. Individual factors can greatly affect the length of time that THC is detectable in the body. Some users may not show detectable levels even with the same dosing as others. It is also possible that certain people may continue to have identifiable levels for much longer than others. In general, heavier or higher potency use will stay in the body considerably longer than single-time or intermittent use.
As you can see, the answer to the question of how long pot stays in the body after use is a complex one. Whether or not an individual will pass or fail a drug test depends on a variety of factors, including the time since last use, the amount or potency used, the frequency of use, individual bodily factors, and other unknown factors. As a general rule, THC is generally detectable for several days even after a single use and may be identifiable for weeks or months afterward.
1. Web-site american.edu, an article about marijuana
URL: Understanding Marijuana | Wellness Center | Office of Campus Life | American University
2. Web-site canorml.org, an article about drugtest detection
URL: Marijuana Drug Test Detection Times | California NORML
3. Web-site cdc.gov
URL: Urine Testing for Detection of Marijuana: An Advisory
5. Web-site urmc.rochester.edu, an encyclopedia
URL: Cannabinoid Screen and Confirmation (Urine) - Health Encyclopedia - University of Rochester Medical Center
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How Long Does Weed Stay In Your System?
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