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Marijuana Detection Time – How Long Does Marijuana Stay In Your System?

Dr. Ted Bender, Ph.D., LCDC

Medically reviewed by

Dr. Ted Bender, Ph.D., LCDC

January 24, 2019

The length of time marijuana stays in the body is different for each person and depends on a variety of factors as well as the kind of test that is being administered.

Marijuana may remain in the body much longer than many other drugs. A common belief is that marijuana can be detected in someone’s system for up to 30 days after the last use. This broad assumption likely does not examine all contributing factors.

The Substance Abuse and Mental Health Services Association (SAMHSA) reports that if someone who regularly uses marijuana stops for 30 days, the drug may still be detected in their urine. After a single use, though, it may only be detected in urine for up to three days.

The length of time marijuana can be detected varies depending on the testing method. While urine testing is most common, other methods of detection include:

  • Blood: After a single use, marijuana may be found in blood for two to three days. With regular use, it may be detected for up to two weeks.
  • Saliva: With single use or repeated use, there may be traces of marijuana in saliva for 12 to 24 hours.
  • Hair: Marijuana may be present in hair for up to 90 days, regardless of how often it is used.

While these are basic guidelines, there are still many more details that can influence how quickly marijuana is expelled from the body.

Factors That Affect Marijuana Detection, Test, and Metabolism

Metabolism is the body’s process of breaking down substances so they can be used or discarded. Marijuana can be found in a person’s system as cannabis or cannabinoids (chemicals that influence the brain). Factors that can affect marijuana metabolism include:

  • dose
  • frequency of use
  • mode of intake
  • body mass index
  • age and health
  • sensitivity or specificity of testing


A high dose of marijuana will stay in the body longer than a low dose. The amount someone ingests at one time may be increased by them taking multiple “hits” or by using a more concentrated form of the substance.

Hash oil,” a substance extracted from the cannabis plant, is made of a concentrated cannabinoid called tetrahydrocannabinol (THC). This will likely produce a more intense effect than a marijuana bud, as each dose of hash oil is more potent. As a result, the concentration of THC in the body will rise and therefore take longer to break down.

Frequency Of Use

The more often someone uses marijuana, the more likely it is to be detected. This is not only because the drug will be freshly present in someone’s system more frequently, but also because repeated use can cause a build-up in the body. Once marijuana begins to accumulate, each successive dose adds to the total body content.

Mode Of Intake

Marijuana may be taken either by smoking or oral ingestion. Smoking takes the drug to the bloodstream and brain very quickly. Eating or drinking marijuana in baked goods or tea causes it to go through the digestive system before it takes effect, possibly after 30 to 60 minutes.

Cannabis consumed by eating or drinking may take longer to break down. When consumed this way, less THC enters the bloodstream and more may be stored in body fat, causing it to linger in the body longer.

Body Mass Index (BMI)

A person’s weight and height can influence how quickly the body processes marijuana. A larger person would likely have to take more of the drug to experience the same effects as a smaller person. This, paired with the likelihood that a larger person also has a slower metabolism, can lead to marijuana being present in someone’s system for a longer period of time.

Age And Health

Generally, younger people have faster metabolisms than older people. They should be able to break down substances like marijuana more quickly. This may be affected by their overall health, though. An unhealthy young person could potentially develop a metabolism that is slower than that of a healthy older person.

Sensitivity Or Specificity Of Testing

Whether or not a drug is detected after a certain period of time may depend on the threshold of testing. If a drug test is looking for the common minimum of 50 ng/ml of cannabis, the result will be negative if there is less than that amount in someone’s system.

Some tests may have a higher or lower limit, which may change the determination of whether marijuana is present in the body after the same time period.

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How Long The Effects Last On The Brain

Cannabinoids interact with receptors in the brain. Tetrahydrocannabinol (THC) is the most common cannabinoid, and is similar to a brain chemical called anandamide. This chemical’s job is to communicate with other areas of the brain to control:

  • pleasure
  • memory
  • thinking
  • concentration
  • movement
  • coordination
  • sensory and time perception

THC interferes with normal functioning of these areas by attaching to cannabinoid receptors and disrupting communication. Over time, the brain may stop producing as much of its natural chemical, as it may become accustomed to THC taking its place.

Prolonged marijuana use may also affect other parts of the brain, possibly stunting the ability to focus, shift attention, or form new memories.

Effects Of Marijuana On The System, Body, and Hair

When someone smokes cannabis, it might be in a joint, blunt, pipe, or water bong. These methods require smoke to be inhaled, which can be damaging to the lungs, possibly causing or worsening asthma or a chronic cough.

Some people smoke marijuana with a vaporizer, which creates a vapor that may be less harsh on the lungs. Hash oil is also turned into a vapor by intense heating before inhalation. This can be dangerous if the oil came from a disreputable source as it may release toxic fumes.

Though rare, chronic marijuana use has been linked to testicular cancer and Cannabinoid Hyperemesis Syndrome, an illness that causes nausea, vomiting, and dehydration. Research is ongoing on the long-term effects of marijuana.

Dangers Of Marijuana Abuse

The high from marijuana can be a pleasant feeling of relaxation. It can also make a person feel anxious, fearful, and paranoid. This may happen when someone takes too much or doesn’t have much experience. In many cases, the effects of marijuana depend on the individual.

With regular use, a person may develop a tolerance to marijuana. As the body adjusts to the substance, it will require more and more of it to produce the same high. This can lead to marijuana use disorder, a mental dependence that can make it difficult for a person to stop using marijuana.

In addition to potentially harming the mind and body, marijuana abuse can adversely affect someone’s lifestyle. Regular cannabis use can inhibit attention, memory, and learning. This may cause poor performance at school or work. It may also promote a less active lifestyle, which can lead to other health issues.

Detection Times, Drug Testing, and Treatment For Marijuana Use Disorder

Marijuana use disorder is a mental disease that can be challenging to overcome alone. Inpatient drug rehab centers offer programs that can help someone who is struggling with a mental dependence on marijuana. These programs may include a variety of treatment methods and can be customized to individual needs.

A marijuana use disorder does not have to interfere with someone’s productivity and health. Exploring treatment options to find the best fit may be the first step to a more fulfilling life.

Contact us today to learn more about marijuana use disorder and treatment options.

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National Institute on Drug Abuse - Marijuana

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