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Swab Drug Test: How Long Does It Detect Weed?

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Written by Sindy Brent on 08/12/2021.
Data Last Updated: 11/22/2022.

Chromometer 7 min

How long does a swab drug test detect weed?

How long after using cannabis can a marijuana test detect it? The answer depends on the testing method you choose. Today, there are several drug testing methods, and each of them can identify the fact of smoking weed in different periods.
The MMJ card provides benefits to its holder - it is a legal way to use medical marijuana if your health condition requires it. Dr.Weedy provides qualified assistance in the arrangement and release of a card on favorable terms.
When talking about drug tests, including tests for marijuana use, experts often use the concept of the Drug Detection Window. If you have any doubts about the swab test, read our recommendations below.


Drug Detection Window

The drug detection window is the time during which a substance can be detected in a patient's biological sample. A biological sample for detecting traces of marijuana is most often:

  • blood;
  • urine;
  • saliva;
  • breathing;
  • hair.

Even though the users of the marijuana card who received it with the assistance of Dr.Weedy or any other legal way are allowed to use cannabis as a medicine, there are cases when it may cause problems. For example, it concerns driving a car under the influence of drugs or performing several works “under the influence of cannabis" when this is unacceptable by law. Therefore, the MMJ program participant needs to know which Drug Detection Window each test has.


Weed testing methods

The window for detecting marijuana in the urine of a chronic smoker, which is the majority of MMJ patients, is 30 days. At the same time, a person who smokes weed from time to time (which is also found among participants of the medical cannabis program) has a much narrower window, and it is usually several days.  In turn, the detection window in the oral fluid is much smaller and is no more than a day. The breath test has an even narrower detection window - only 3 hours. It is really possible to detect the content of marijuana in the body during a breath test only at the time of actual drug intoxication of the person undergoing the test.

The choice of a marijuana test depends on the specific circumstances. If the tester’s task is to understand whether a person is currently in a state of drug intoxication, then a breath test will be the optimal choice. If the aim is to identify whether a person smokes marijuana daily, then tests with a broader Drug Detection Window are involved.

Patients of the MMJ program should remember that cannabis has the property of accumulating in adipose tissue, unlike alcohol and other substances. Due to this, the period of complete elimination from the body is quite long. Therefore, many tests allow you to detect tetrahydrocannabinol or its metabolites after a long period since the last use.

Various types of tests are presented below to understand better the probability of detecting THC or metabolites in certain biological materials.


This method of detecting marijuana is distinguished by the shortest Drug Detection Window, which does not exceed several hours. Tetrahydrocannabinol enters the bloodstream and is then discovered when breathing. Therefore, breathing is considered the best way to determine the recent use of weed.

When inhaling (smoking or vaping) marijuana, THC enters the bloodstream within a few seconds and is exhaled through the lungs. The level of THC in the breath shows the recent use of weed. As for the use of cannabis in edible form, then, THC passes through the liver, after which it enters the bloodstream. A breath test will detect the content of weed in the body within an hour after consuming an edible form of marijuana. MMJ patients who prefer edible forms of cannabis should keep in mind that in this case, the detection window is several hours longer than when smoking or vaping.


Oral Fluids

Tetrahydrocannabinol remains in saliva during the day because the substance settles in the oral cavity when smoking, steaming, or eating. THC enters the oral mucosa, after which it is excreted through saliva for 24 hours. This testing method is quite sensitive to the recent use of weed, but it is not comparable with the “breathing” test for the narrowness of the window.


After using marijuana, its psychoactive substance of tetrahydrocannabinol enters the bloodstream and is absorbed by the tissues, where it remains for a long time. Gradually, the substance is released from the tissues, and therefore it can be detected in the blood. At the same time, there is less amount of THC than in the first few hours after consumption. This amount depends not only on the time and dose of use but also on physiological characteristics and behavioral factors.



The urine test is a problem for the medical cannabis program patients because it does not detect THC but its inactive metabolites. There are several dozens of these metabolites. They remain in the body much longer than tetrahydrocannabinol. The test is usually intended to detect THC-COOH. At the same time, the content of metabolites in the blood test depends not only on the dose consumed and the frequency of use but also on the physiological and behavioral characteristics of the patient.



A drug test using hair as a biological material has the most expansive Drug Detection Window, which is up to 90 days. Similar to urine tests, hair tests do not detect tetrahydrocannabinol itself but its inactive metabolites. At the same time, there is a loophole in this test for MMJ patients - the fact of use can be detected through a hair test within only 7 days after the actual smoking or other forms of consumption.

Mouth Swab Test

Mouth Swab Test is the easiest way to test for drugs, and therefore one of the most common. The procedure of collecting biological material is as follows: the inner surface of the cheek is wiped with a conventional cotton swab. The biomaterial is processed by enzyme immunoassay in the laboratory for the presence of inactive THC metabolites. A positive test for additional clarification is tested by chromatography or mass spectrometry.

The window of drug detection by the Mouth Swab Test depends on the specific substance. If we are talking about cannabis, the window is only a few hours after use.

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