In an effort to provide the most accurate answer to this question, we set up a simple submission form where people can report their drug test results. This study started in 2011, and since then, we’ve received thousands of responses. With this data, we were able to develop the world’s only drug test passing probability calculator, which has provided millions of calculations. Navigate to the Marijuana Drug Test Calculator to determine your odds of passing your next drug test.

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As you probably know, tetrahydrocannabinol, commonly known as THC, is the primary chemical compound found in marijuana that is responsible for the euphoric “high” its users experience. It is an extremely hydrophobic (water fearing) organic compound that is metabolized and broken down by the body into about 80 different metabolites. Because of the hydrophobic nature of these metabolites, polar molecules like water can’t “stick” to and dissolve them, like they do when breaking alcohol down. Instead, these metabolites associate themselves with other non-polar compounds, such as alkanes, oils, and body fat – where THC is stored.

If you are trying to pass a marijuana drug test of any sort, it is important that you understand how long it can remain detectable in your body. As five of these metabolites, with THC-COOH being the primary one, are targeted by a multi-billion dollar drug testing industry that specializes in trying to make a buck off of invading your privacy at every corner. And make no mistake, they are very good at it. Unfortunately for those that use marijuana, it can take a considerable amount of time for these compounds to drop below detectable levels.

THC Concentration Levels After Consumption

Smoking is the most common way of using marijuana for the general population. After inhalation, tetrahydrocannabinol (THC) quickly enters the blood stream through the lungs. With rapid circulation of the blood, this compound, in conjunction with a myriad of others, including CBD, act almost instantly on the human endocannabiniod system by interacting with CB1 and CB2 receptors located throughout the body.

THC has been found to be immediately detectable, with blood levels of THC reaching a peak at around 9.0 minutes into smoking. In the referenced study, it took between 3 to 12 hours for THC to drop below detection limits for the low-dose group and from 6 to 27 hours for the high-dose group of the study. However, the subjects of this study were not regular marijuana smokers, which explains why THC levels fell so quickly. Keep in mind, this is based on blood detection. Urine detection is a different story.

Marijuana THC & THC-COOH Compounds

Generally, active THC blood concentrations decrease rapidly after you finish smoking due to its fast uptake into tissues. However, if the uptake tissues are saturated with THC, it isn’t uncommon for blood levels of active THC to remain high for several days in chronic marijuana users. This is because over time, these fatty tissues leach THC molecules back into the blood stream (increasing the blood detection window), where the liver continues metabolizing them into non-psychoactive, THC-COOH derivatives for your body to pass (increasing the urine detection window).

Marijuana Detection Times

Drug tests for THC in the body can be divided into two categories, historical use and present intoxication. Historical use includes the infamous urine drug test along with the hair follicle test. These tests almost always target the THC-COOH molecule, a non-psychoactive substance that has absolutely nothing to do with a person’s level of sobriety; used only to determine if someone used the substance in the past, regardless if use was during personal time.

To detect present intoxication, the blood serum and saliva tests are typically employed. These tests indicate whether or not active THC molecules are present, therefore being an indicator of “being impared,” despite the users’ level of tolerance (note: marijuana is not alcohol, therefore marijuana tolerance is not comparible to alcohol tolerance). These type of tests are supposed to be accurate to within a couple of days, but that is under heavy scrutiny. For instance, it can literally take days for a healthy, chronic marijuana user’s THC levels to drop below 5 ng/mL of blood. Five nanograms of THC per mililiter of blood being the poorly researched DUI limit that a group of circle jerking lawyers pulled out of a German study and slapped into law books in Colorado and Washington. Here’s an excellent article covering the DUI background of what’s going on in Colorado.

Below is a breakdown of the methods through which THC metabolites are tested.

Table: Marijuana Use and Approximate Detection Times

Present Intoxication

Historical Use





Single Use

0 – 24 Hours

6 – 24 Hours


Drug Test Calculator

Regular Use

0 – 24 Hours

Up to 7 Days

3 Months

Urinalysis Drug Testing

This is the most common drug test. The test is quite easy and all that is required is a sample of urine by the subject for the test to be carried out. The sample is first taken to the laboratory then screened under a threshold sensitivity level. If the targeted metabolites (THC-COOH) of the test are found to be below the national standard of 50 ng/mL, then the sample is marked negative and you pass the test! However, if it’s higher than 50 ng/mL, then the sample is tested a second time for confirmation.

The second test is conducted with the use of more advanced equipment. Typically, a Gas Chromatography/Mass Spectrometer (GC/MS) is used. This test is analyzed under a threshold of 15 ng/ml, which makes the result very accurate. If the sample is higher than this, then “Test Positive for Marijuana” is reported.

How long is THC detectable in urine? If you are a chronic marijuana user, THC can be detected in your system using a urine test for up to 12 weeks depending on the quantity as well as frequency of use. Note that if you just used marijuana once and stopped, the odds of passing a test within the first week are decent but you can still test positive for up to 30 days.

Hair Follicle Drug Testing

Although hair testing is more accurate compared to the other tests, it is relatively expensive and not reliable if a person only used marijuana once in the past. However, the advantage this test has over all others is that it can be used to detect the use of marijuana for months. Just an inch of hair from a person’s scalp is all specialists need for the test. And hair from any other part of the body can still be used – the pubic area, arms and legs.

Blood Serum Drug Testing

This is type of test is used to detect current usage of drugs such as marijuana. It also helps to investigate car/work accidents. After a single use of marijuana, the blood test can produce positive results for 6-24 hours. However, for regular users, a blood test can produce positive results for up to 7 days or more.

Saliva Drug Testing

This is the newest test for marijuana usage and hence not commonly used. Usually, it is used to investigate car and work accidents. This is because the test can detect whether a person is under the influence of marijuana or not. A saliva test can produce positive results within the first 24 hours of its usage.

Korban Stone | LinkedIn Twitter Social

Founder & CEO of Marijuana Central and creator of the world's only data-driven cannabis drug test passing probability calculator, utilized by an international audience in the millions. Subject matter expert and author of several topics relating to the detection time of cannabis in the body, the worldwide use of cannabis as an entheogen, and how drug testing impacts minorities and other groups of people who consume the herb.