How long is marijuana detected in the blood?

Marijuana can take anywhere from a couple of weeks to several months to clear from your system. It all depends on the habit of consumption and the concentration inhaled or ingested.

Last update: February 12, 2022

Marijuana, also called cannabis or hashish, is a psychotropic substance of natural origin that acts as a depressant of the nervous system. In general, it is usually consumed by the respiratory route or in edible preparations. But how long is marijuana detected in the blood?

Currently, studies estimate that Marijuana is one of the most used drugs in the world for recreational and medicinal purposes. Beyond its effects on the body, this substance can be detected in body fluids for 1 to 30 days after its last use.

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 the frequency of use.

How long is marijuana detectable through blood tests?

Drug testing uses 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 symptoms typical of cannabis use.

Common blood marijuana screening tests focus on identifying THC and its metabolites, such as THC-COOH. There is talk of a positive blood test for cannabis when THC levels are equal to or greater than 0.5 nanograms per milliliter (ng/ml).

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

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

Marijuana blood screening can be used for legal purposes. It is even mandatory for certain procedures, depending on the country.

Marijuana detection times in other samples

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

Urine analysis

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

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

  • Occasional consumption (2 to 3 times a week): it is detected up to 3 days later.
  • Moderate use (4 times a 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 take marijuana in food or drink to treat chronic pain may have a positive urine result for up to 5 to 6 days. Both the inhaled and ingested forms are capable of binding to fat cells in the body and delaying their elimination.

saliva analysis

Saliva tests are useful for detecting recent drug use. In most cases, this test can be positive for up to 34 to 48 hours.

Cannabis can be lodged in saliva both from smoking and from 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 last use.
  • Chronic: 1 to 29 days after consumption.

hair test

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

Hair grows at a rate of 0.5 inches per month, so a 1.5-inch piece of hair harvested close to the scalp can offer up to a 90-day window of suspicion for use.



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 determines the appearance of the first symptoms in just 15 to 30 minutes, and then disappear after 1 to 3 hours. For its part, when this drug is ingested, the symptoms can take between 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 longer. On the other hand, a large part of the 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 the detection tests can be positive for many more days than expected.

THC reaches the brain quickly and can then be stored in fatty tissue for several days.

Factors that affect how long marijuana stays in the blood

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

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

  • Quantity consumed.
  • Frequency of use.
  • Nutritional condition.
  • Hydration level.
  • Presence or absence of metabolic disease.


Is it possible to remove marijuana from the blood faster?

There is no effective method to speed up the time it takes for marijuana to leave the blood. In this sense, the body requires a reasonable amount of time to break down cannabis and eliminate it completely.

Exercising, following a healthy diet, and increasing your water intake can help, but it will not drastically disappear marijuana. In addition, there are some commercial detox kits to fulfill this function. However, they do not have reliable scientific support.

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