How Long Does Marijuana Stay in your System

The effects of cannabis may fade quickly after ingestion, but its active ingredient, tetrahydrocannabinol, can remain and be detected in the body for weeks, and maybe even longer. This shall depend on how the substance is metabolized.

Some tetrahydrocannabinol metabolites have an elimination half life of 20 hours, while others are stored in body fat and have elimination half lives of 10 to 13 days. Half lives may be influenced by how heavy the person weighs, how often he uses the drug, how much he consumes, and how long has he used it. [18]

Retention time of orally ingested marijuana ranges from 1 to 5 days. [19] Occasional smokers can take cannabis out of their system within just a few days. For regular heavy smokers, it will take 2 weeks to a month before drug levels reach nil. Those chronic users, who smoke weed on a daily basis, may still have it in their bodies even 2 to 3 months after their last consumption. [20]

How Long Does Marijuana Stay In Your Hair?

  • It takes approximately 7-10 days from the time of Cannabis use for the affected hair to grow above the scalp.
  • Detection of the drug can still be achieved until 90 days from the most recent use.[21, 22]
  • How Long Does Marijuana Stay In Your Blood? [23, 24]
  • Cannabis may be present in the blood approximately 2 to 3 days after its use. However, this can remain in the bloodstream after 2 to 3 weeks if done with frequent and heavy use.

How Long Does Marijuana Stay In Your Saliva?

  • There is a shorter window period for detection of marijuana in the saliva.
  • Presence of Cannabis may only be noted for only a period of one to two hours following drug ingestion.
  • This may also depend on where the saliva testing was done. If the sample was tested inside a laboratory, where the used detection level is as low as 0.5ng/ml, the drug can be detected up to 72 hours after intake. This is compared to that which was done onsite using an instant saliva drug test, with cutoff levels higher, cannabis can still be perceived from the sample only after 12 hours from last drug ingestion. [25, 26, 27]

How Long Does Marijuana Stay In Your Urine?

Cannabis level determination in the urine is strongly influenced by the amount and frequency the drug is used.
It can be identified in the urine 2 to 5 days after exposure among infrequent users, around 15 days for heavy users, and a minimum of 30 days for chronic users, or those with high body fat. [21, 28, 29]

Marijuana Testing

The common drug tests for detecting Cannabis include examinations using the hair, blood, saliva, and urine. The test results of which are significantly influenced by factors such as weight, body fat, amount ingested, and frequency of use. [29]

Hair Test

  • Cannabis hair test is generally included in the standard drug hair test.
  • It measures the marijuana parent metabolite at the hair shaft, further eliminating possibility of external contamination. [30]
  • Hair specimen is easier to collect, store and transport. [30]
  • In this test, the most recent 1.5 inches of hair growth is taken and used for testing. [21]
  • If an individual’s hair is shorter than 1.5 inches, the detection period can also be shorter.
  • If the sample is body hair, the period for detection will be longer, since body hair growth is slower than scalp hair. [30]
  • Test results cannot be affected by the use of shampoos, bleaches or other external chemicals. [30]
  • Detection window of hair testing is as low as 1pg/mg. [31]

Blood Test

  • Difficult to administer and invasive, marijuana blood test is used less frequently. [32]
  • It has a narrow detection window, determining the presence of illicit drugs, not active drug metabolites. [25]
  • High tetrahydrocannabinol level in blood is a good indication that the subject took marijuana quite recently. [23]
  • These are typically used in investigations of accidents, injuries and driving under the influence (DUI) cases, in which they can indicate whether the subject was actually under the influence at the time of the incident. [23]

blood test for marijuana picture

Picture – blood test for marijuana

Saliva Test

  • It is a newer and, hence, less proven technology. [23]
  • The procedure detects the presence of the parent drug and not the active metabolite, thus, it has a shorter window of detection. [25]
  • Active metabolite tetrahydrocannabinol is difficult to identify in oral fluids, since only a small amount of the drug can be excreted in the saliva. [25]
  • Test results can be readily available after 10 to 12 minutes, with cutoff levels of 25ng/ml. [33]

saliva test for marijuana image

Picture : saliva test for marijuana

Urine Test

  • This is the most popular and the most reliable test used to date. [34]
  • It can detect marijuana for days or weeks after ingestion, using the non-psychoactive metabolite THC-COOH levels. [23]
  • Urine samples are screened at a threshold sensitivity of 50ng/ml. [34]
  • Positive results are then confirmed by Gas Chromatography/ Mass Spectrometry. [34]

urine test for marijuana picture

Picture:urine test for marijuana

Inaccuracy of Marijuana Test Results

Inaccurate test results can occur for a number of reasons: mishandling of specimen samples, passive inhalation, improper diagnostic procedure, and, the most common of which, presence of cross reactants.

False Positives

  • Pantoprazole sodium
  • Non steroidal Anti-inflammatory Drugs (NSAIDs)
  • Dronabinol
  • Hemp seed oil
  • Kidney disease
  • Diabetes
  • Liver disease
  • Riboflavin [35]

False Negatives

  • Excessive fluid intake
  • Household chemicals
  • Acids
  • Vinegar
  • Lemon juice
  • Table salt
  • Eye drops
  • Cranberry pills [36]

Marijuana: Just the Facts

  • Medically known as Cannabis, Marijuana is a known psychoactive drug derived and named after the Cannabis sativa plant. [1]
  • The Cannabis plants were thought to originate from the Central Asia valleys and the Himalayas of South Asia during the 6000 BC. [2,3]
  • At 2737 BC, it was first used by the Chinese emperor as a medicinal plant for arthritis and pain. [4]
  • Cannabis hemp plants were grown to make clothing, sail and ropes. [5]
  • From 1850 to 1942, marijuana can be bought from the pharmacy or at a local store as an over the counter medication for nausea, labor pains, and rheumatism. [5]
  • During the turn of the century, the drug has been subjected to legal restrictions with possession, use, and sale of cannabis preparations currently illegal in most regions of the world. [6]
  • The Controlled Substances Act of 1970 states that it is illegal to possess, use, buy, sell or cultivate marijuana in the United States. The drug was classified as a Schedule Drug 1, with high potential for abuse but no acceptable medical use. [7]

Marijuana photo

  • However, based on a survey done by the United Nations, 158.8 million people worldwide — or approximately more than 3.8% of the earth’s population — use marijuana, even if it is still not legalized in all countries. [8]
  • This makes cannabis the third most popular recreational drug in the United States, behind alcohol and tobacco. [9]
  • At present, this illicit drug is commonly known as weed, pot, hash, joint, dope, Mary Jane, Aunt Mary, smoke, bud, BC, blunts, grass, skunk, reefer, yerba, boom, chronic, ganja, gangster, hydro, kif, indo, and sinsemilla. [10]

cannabis in the world picture

Picture – cannabis in the world

Effects of Marijuana

  • Cannabis owes its potent psychoactive properties from its main chemical component Tetrahydrocannabinol (THC). [11]
  • When the drug is ingested or smoked, the tetrahydrocannabinol (THC) binds at the cannabinoid receptors present throughout the brain, resulting in both psychological and physical effects. [12,13]
  • These effects depend on the dose, frequency, route of administration, body mass index, age, co-morbidities, drug tolerance, and other drugs and medications concurrently taken. [14]

effects of marijuana on body image

Picture – effects of marijuana on body

Short Term or Immediate Effects

  • Marijuana affects both the brain and the body. Generally, these effects are reduced after 3 to 4 hours. However, residual effects can last for a few days, more so if mixed with other medications. [15,16,17]
  • Tachycardia or rapid heart rate
  • Hypertension or increased blood pressure
  • Tachypnea or increased rate of breathing
  • Red eyes
  • Dry mouth
  • Increased appetite
  • Slowed reaction time
  • Distorted perceptions of time, sounds and sights
  • Paranoia
  • Magical thinking
  • Cognitive problems
  • Short term memory loss
  • Anxiety and depression
  • Loss of coordination

Long Term Effects

  • Taken regularly over a long period of time, Cannabis may produce such serious effects. [8, 14, 17]
  • Dependence
  • Reduced resistance to common illnesses (colds, bronchitis)
  • Suppression of immune system
  • Decreased motivation
  • Decreased sex drive
  • Schizophrenia
  • Growth disorders
  • Increase of abnormally structured cells in the body
  • Reduction of male sex hormones
  • Reduced ability to learn and retain information
  • Apathy and drowsiness
  • Personality and mood changes

Marijuana Addiction and Withdrawal

  • When physical and psychological dependence to cannabis occur, withdrawal symptoms may be observed once drug use was abruptly stopped or dose was decreased. [14]
  • Those who were daily cannabis smokers experience the most symptoms. [18]
  • It generally lasts for 5 to 7 days depending on the amount and length of marijuana use. [37]
  • Manifestations are generally mild, and are mostly flu-like: headache, nausea, poor appetite, restlessness, depression, anxiety and trouble sleeping. [14]
  • Other symptoms of withdrawal include craving, mood swings, strange dreams, physical tension, weight loss or gain, abdominal pain, digestion problems, decreased sex drive, shaking, and dizziness. [37]
  • These symptoms are most severe during the first few days of withdrawal. [37]
  • Depending on how much and how often one had been using marijuana, manifestations of withdrawal can be intense enough to force relapse. [38]
  • Support groups like Marijuana Anonymous can be of help to handle psychological manifestations. [38]

Marijuana Uses: The Other Side of the Story

Last November 2012, Colorado and Washington States passed a legislation that legalizes the recreational use of marijuana. Studies are being done to support this proposal and, at the same time, prove that aside from recreation, the drug also has the said medical uses and benefits. [39]

recreational use of marijuana image

  • Prevents blindness due to glaucoma
  • Increases lung capacity
  • Prevents epileptic seizures
  • Stops cancer from spreading
  • Decreases anxiety
  • Slows the progression of Alzheimer’s Disease
  • Eases the pain of Multiple Sclerosis
  • Lessens the side effects in Hepatitis C treatment
  • Treats inflammatory bowel diseases
  • Relieves arthritis discomfort


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  2. El-Sohly, M. 2007. Marijuana and the Cannabinoids. Totowa, NJ: Humana Press.
  3. Rudgley, R. Lost Civilizations of the Stone Age. New York Free Press. 1998
  4. Abel, el. 1980. Marijuana: The First Twelve Thousand Years. New York, NY:Plenum Press
  5. Booth, M. 2003. Cannabis: A History. London, England: Doubleday.
  6. Cannabis: Legal Status. 2011 Oct.
  7. United States Office of National Drug Policy. Marijuana Facts and Figures. 2009.
  10. Drug Fact Sheet: Marijuana.
  11. Grotenhermen, F, et al. 2002. Cannabis and Cannabinoids: Pharmacology, Toxicology, and Therapeutic Potential. London: Routledge.
  12. Connor, P. 2012. Marijuana (cannabis).
  13. Rull, G. 2011. Cannabis Use and Abuse.
  17. Weil, A. Clinical and Psychological Effects of Marijuana in Man. Science. 1968 Dec; 162: 1234-42.
  21. Erowid Cannabis (Marijuana) Vault: Drug Testing. 2010.
  23. Marijuana Drug Detection Times.
  25. Armentano, P. The ABCs of Marijuana and Drug Testing.
  26. Forensic Fluids Laboratory. Journal of Analytical Toxicology. 2002 Nov/Dec. (25)
  28. Armentano, P. Marijuana Detection Time Shorter Than Previously Assumed. 2006 Feb.
    Green, J. How Long Does Marijuana Stay In Your System? Infographic. 2013 January.
  34. The Marijuana THC Calculator.
  35. Meininger,k. What Causes False Positives In Marijuana Drug Testing. 2011 March.
  36. Face Your Drug Test With Confidence. 2010 Nov.
  38. Detoxing from Marijuana. Marijuana Anonymous World Services.. 2012 June.
  39. Astaiza, R. All the Reasons Pot is Good For You. 2012 Nov.
How Long Does Marijuana Stay in your System
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Published on by under Addiction and Withdrawals.
Article was last reviewed on February 18th, 2018.

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