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How long is marijuana detected in the blood?

Health & FitnessHow long is marijuana detected in the blood?

Marijuana, also called cannabis or hashish, is a naturally occurring psychotropic substance that acts as a nervous system depressant.

Currently, studies estimate that marijuana is one of the most widely used drugs worldwide for recreational and medicinal purposes. It is usually consumed via the respiratory tract or in edible preparations.

Blood, urine, saliva and hair are the main sources for the identification and measurement of marijuana in the body. The detection period varies according to the amount consumed and frequency of use.

How long is marijuana detectable through blood tests?

Drug tests use chemicals to measure the concentration of marijuana or its metabolites in different samples and body fluids. Delta-9-tetrahydrocannabinol (THC) is the active ingredient responsible for the typical symptoms of cannabis use.

The usual blood tests for marijuana focus on the identification of THC and its metabolites, such as THC-COOH. A blood test is positive for cannabis when THC levels are equal to or greater than 0.5 nanograms per milliliter (ng/ml).

The detection time in the blood varies considerably depending on age, dose, frequency of use and metabolism. Studies claim that marijuana is detectable in the blood for 1 to 2 days. Other laboratories estimate that THC can appear in blood plasma for up to 36 hours.

In addition, the International Association for Cannabinoid Medicines states that the elimination half-life of cannabis metabolites is longer than that of THC. In this regard, with regular use, THC-COOH can be identified in blood several weeks after the last use.

Detection times of marijuana in other samples

Marijuana is also traceable in tissues other than blood. Let’s see what happens in urine, saliva and hair.


Urinalysis is the most commonly used drug screening test. In most cases, a positive result indicates recent or past marijuana use. In this regard, a positive test occurs when THC levels in the sample are greater than 50 nanograms per milliliter (ng/ml).

Research suggests that the amount and time of detection of THC and other cannabis metabolites in the body varies greatly depending on the person’s habit of use. Thus, marijuana can be identified in urine according to the following patterns:

  • Occasional use (2 to 3 times per week): detected up to 3 days later.
  • Moderate use (4 times per week): 4 – 7 days.
  • Chronic use (once a day, every day): 7 – 21 days.
  • Chronic intensive use (several times a day, every day): 1 month or more.

On the other hand, people who ingest marijuana in food or drink to treat chronic pain may get a positive urine test for up to 5 – 6 days. Both the inhaled and ingested forms are able to bind to fat cells in the body and delay their elimination.

Saliva testing

Saliva testing is useful for the detection of recent drug use. In most cases, this test can be positive for up to 34 to 48 hours.

Cannabis can become lodged in saliva from both smoking and exposure to smoke. However, the test is only positive when it has been smoked or ingested.

On the other hand, some research suggests that the presence of cannabis and some of its metabolites in oral secretions varies according to the following consumption patterns:

  • Occasional: 1 to 3 days after the last use.
  • Chronic: 1 to 29 days after use.

Hair Test

Marijuana metabolites are able to reach hair follicles through blood circulation. This generates traces of cannabis that are the target for identification in this type of testing.

Hair grows at a rate of 0.5 inches per month, so a 1.5-inch piece of hair obtained near the scalp can provide a window of suspicion for use of up to 90 days.

How does your body process marijuana and how long does it take to metabolize it?

When a person smokes marijuana, the THC found in the plant passes directly from the lungs into the blood. In this way, the drug is able to distribute throughout the body and reach the endocannabinoid system in the brain.

In this sense, the inhalation of cannabis causes the appearance of the first symptoms in only 15 to 30 minutes, and then disappears after 1 to 3 hours. On the other hand, when this drug is ingested, symptoms may take 30 minutes to 1 hour to appear.

THC can also be absorbed by the heart and fatty tissue to be released gradually, maintaining the effect of the drug for a longer period of time. On the other hand, a large portion of free marijuana in the blood is metabolized directly in the liver, forming more than 80 metabolites.

In chronic users, THC accumulates in fat faster than it is metabolized and eliminated. This determines that screening tests can be positive for many more days than expected.

Factors affecting the time marijuana remains in the bloodstream

There are several factors that condition the time marijuana remains in the blood. On the one hand, intrinsic factors such as age, sex and body mass index (BMI).

Similarly, the purity of the drug and the way it is consumed (inhaled or ingested) also affect the detection window of marijuana in blood. Other factors involved are the following:

  • Amount consumed.
  • Frequency of use.
  • Nutritional status.
  • Hydration level.
  • Presence or absence of metabolic disease.

Is it possible to eliminate marijuana from the blood faster?

There is no effective method to speed up the time it takes for marijuana to leave the bloodstream. In this sense, the body requires a prudent time to break down the cannabis and eliminate it in its entirety.

Exercising, eating a healthy diet and increasing water intake may help, but it will not make the marijuana disappear drastically. In addition, there are some commercial detox kits available to accomplish this function. However, they do not have reliable scientific support.


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