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How Long Does Weed Stay In Your System?

Marijuana THC Drug Test CalculatorIt's no joke - this is a serious question that many have asked as well as one that tax payers ultimately pay for. Because so many sources have provided input to this difficult question, the answer has turned into a convoluted and obfuscated range that no one is sure about (with the exception of our calculator). However, the question we're asking needs to be reframed.

Tetrahydrocannabinol (THC) is the primary chemical compound found in marijuana that gets users high and it's the metabolites of THC that are detected for marijuana use. After ingestion, THC quickly enters the blood flow where the body starts not only to break the compound down, but to store it in order to continue the process at a later time. Due to the lipid soluble nature of these cannabinol-based compounds, this process takes many days (this is also the most important reason why the Drug Testing Industry has expanded to the size that it is today). Without getting into detail about the endocannabinoid system and how vital it is for human development, it may surprise you when the real answer to the question above is that marijuana usage just might be detectable forever! This is because our bodies, including human breast milk, naturally produces many of the same compounds found in marijuana. Yes, we're splitting hairs here but we've identified that some sort of acceptable threshold level needs to be determined. Since people who ask this question are more concerned with the length of time marijuana use can be detected in their body. We come to our revised question:

How Long Can THC Metabolites Be Detected In Your Body?

There are four methods in which marijuana use can be detected. These methods are separated into two categories. The first category contains the methods that are used to test whether a user is currently under the influence of marijuana. This includes the saliva test and the blood test.

Urinalysis Cup Filled with Yellow Wizz The saliva test is the newest form of testing for marijuana. It hasn't been as established as other methods so it's not widely used. A saliva test can detect recent marijuana use up to 24 hours and is used to investigate car/work accidents. The blood test is also used to investigate similar accidents. However, it is used more often than the saliva test (for now). For a single use of marijuana, a blood test can produce a positive result for 6-24 hours. Unfortunately, for people who regularly use marijuana, a blood test can produce positive results for up to 7 days, which brings question to it's accuracy.

The second category contains the methods that are used to test whether a person has used marijuana in the past. This includes the hair test and the urine test.

The hair test was once rarely used because of two factors: 1) The cost of analysis is relatively expensive when compared to urine testing and 2) Its use isn't suitable or reliable for a person who only used marijuana once or twice, which is very common. However, due to current events concerning the legality of marijuana, there has been an increase in its application. Generally, it can be used to detect regular marijuana use for months. At least an inch of hair is usually required from a person's scalp but hair can be collected from any part of the body - the arms, legs, or pubic areas.

The most popular and reliable test used today is the urinary analysis test. When a subject provides a urine sample to a laboratory, it has the potential to go through two processes. First, the sample is screened at a threshold sensitivity level of 50 nanograms of THC metabolites per milliliter. If the targeted metabolites of the test are found to be greater than 50 ng/mL, it is marked as "suspect" (otherwise results are reported back as "negative"). When a "suspect" test has been identified, the sample is tested a second time with the use of Gas Chromatography/Mass Spectrometry (GC/MS) at a threshold sensitivity level of 15 ng/mL. GC/MS is very accurate and the result that GC/MS produces is what is reported. This two step method is used in order to reduce the occurrence of false-positives. Under rare circumstances, a threshold sensitivity level of 20 ng/mL may be used for the first part of the urine test. At this level, the detection window for marijuana use increases. We're aware of this but are confident that data submitted from these rare circumstances will be flagged as outliers and removed from analysis when necessary.

Now we'll provide our answer and get straight to the point: No one can tell you how long THC metabolites can be detected in your body with absolution because of the many variables that are involved. However, with a sample size large enough, it is possible to detect patterns through the use of statistical analysis in order to provide a probability that is useful (think of a weather forecast and the chance of rain). After collecting drug test data from thousands of users over the past few years, this is exactly what we've done and this is what our calculator is for.

Table: Drug Test Types and Approximate Detection Times



To Detect Present Intoxication

To Detect Past Use


Marijuana - Single Use

0 - 24 Hours
6 - 24 Hours

Marijuana - Regular Use

0 - 24 Hours
Up to 7 Days
Months to Years


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