Typically, THC is detectable for up to 90 days in hair, anywhere between 3 days to a month or longer in urine (depending on how often the person uses), up to 48 hours in saliva, and up to 36 hours in blood. Regular marijuana use can lead to dependence and withdrawal. Quitting can be challenging, but with the right treatment, recovery is possible.
What Is Marijuana?
Marijuana, sometimes referred to as weed, pot, and ganja, is a psychoactive drug derived from the cannabis sativa plant. It is the most commonly used illegal drug in the United States, according to the National Institute on Drug Abuse (NIDA).1,2 In 2017, about 26 million Americans age 12 and older had used marijuana in the past month, which is equivalent to 9.6% of this population.3
Marijuana is most commonly smoked in pipes, joints, or bongs. It can also be smoked in blunts, which are cigars that have had their tobacco removed and replaced with marijuana. In addition, people sometimes add marijuana to food or brew it as a tea.2
What Happens When You Smoke It?
THC (delta-9-tetrahydrocannabinol) is believed to be the primary mind-altering chemical found in the cannabis plant. When a person smokes marijuana, THC passes from the lungs into the bloodstream, where it is carried to the brain and other organs. Via its interaction with the endocannabinoid system, THC affects areas of the brain related to movement, sensations, coordination, memory, reward, and judgment.1,2
When smoked, the effects are felt right away and generally last for 1 or 3 hours. When eaten, such as in brownies, a person may not feel the effects for 30 minutes to an hour, and the effects can last for several hours.4
Some effects that people may experience from using marijuana include:1,4
- Altered senses.
- Distorted sense of time.
- Impaired coordination.
- Trouble thinking clearly or solving problems.
- Trouble remembering things.
- Mood swings.
- Increased appetite.
How Does Your Body Process THC?
THC is absorbed into various body tissues and organs (e.g., the brain, heart, and in fat) or metabolized by the liver into 11-hydroxy-THC and carboxy-THC (metabolites). The metabolites are quickly excreted in urine.5
Over time, THC that is stored in body tissues is released back into the bloodstream, where it is eventually metabolized by the liver. In chronic users, THC builds up in fatty tissues faster than it can be eliminated, which means a heavy smoker could test positive for marijuana use many days after they stopped using.5
When Will Marijuana Show Up on a Drug Test?
Several different sampling types are used to test for the presence of marijuana. These tests vary in the timeframe during which they can detect marijuana and its metabolites in a person’s system.
- Saliva test: A person can test positive for weed for up to 34-48 hours after last use.6,7
- Urine test: This is the most common drug test used. Infrequent users (less than 2 times/week) can test positive for 1-3 days. A moderate user (several times per week) can test positive for 7–21 days after last use. A heavy user can test positive for a month or longer after last use. People who eat marijuana may produce a positive result for 1-5 days.5
- Hair test: Marijuana can be detected on a hair test for up to 90 days. However, studies have argued that a hair test is most reliable for daily or near-daily users and is not as likely to detect the presence of marijuana in light users.8,9
- Blood test: Marijuana and its metabolites can show up on a blood test for up to 36 hours.6
Besides the type of test, other factors that can affect how long marijuana will show up on a drug screen include:5
- Amount of THC in the marijuana.
- Frequency of use.
- Length of time since last use.
- How quickly the person’s system processes THC.
- Level of hydration.
Attempting to Beat a Drug TestDetoxification kits are popular with people attempting to pass drug tests. Many such kits are tailored to help people pass urine tests and may consist of adulterants such as goldenseal, vinegar, niacin, vitamin C, or herbal teas. In general, however, these kits do nothing to speed up the metabolism and clearance of marijuana from a person’s system and will not help someone pass a drug test.10
Other attempted methods of evading a positive drug screening include masking the urine sample with a chemical, such as salt or bleach, or submitting a urine sample that isn’t theirs (either synthetic urine or someone else’s). However, if a urine integrity test is used, it can detect masking agents as well as compounds that are normally found in human urine, such as cortisol. It can also test for temperature, pH, color, gravity, smell, or dilution of the urine. So these methods are not foolproof ways to pass a test, either.10
In short, going to these great lengths to cheat a drug test may be unwise—many so-called “detox kits” do not work and some may even contain ingredients that could be dangerous.
A 2011 study presented the case of a man who developed psychotic symptoms after using a home detox kit. After review, the study’s authors found that many of the ingredients in the kit could cause liver dysfunction, even though the product did not specify the doses of the ingredients on the label. In addition, creatine, one of the ingredients in the kit, had been reported to cause acute psychosis in other case studies. Though the origin of the psychosis was never explained, the authors saw a strong link between the use of the kit and the onset of the man’s psychotic episode.11
Detoxing from Weed
A combination of behavioral therapy and medications may be effective in treating marijuana use disorder.
Contrary to popular belief, marijuana can be addictive. Healthcare practitioners diagnose marijuana addiction based on the presence of certain signs, symptoms, and behavioral changes. In those that meet the diagnostic criteria, marijuana addiction is referred to as a marijuana use disorder or cannabis use disorder. People with the disorder have trouble stopping their use of the drug even though it causes problems in many areas of their lives.12
According to NIDA, approximately 30% of people who use marijuana will go on to develop a marijuana use disorder. People who begin using the drug before 18 years old are 4 to 7 times more likely to develop an addiction to the drug than those who begin using it in adulthood.12
Many people who become addicted to marijuana develop dependence, which means a person’s body comes to rely on the substance to function normally. When a dependent person suddenly stops using marijuana, they can develop withdrawal symptoms.12
The symptoms of marijuana withdrawal typically begin within 24-72 hours after last use, peak in intensity during the first week, and last 1-2 weeks. Marijuana-associated withdrawal symptoms include:13
- Poor sleep.
- Abdominal pain.
- Decreased appetite.
There are not currently any FDA-approved medications that specifically treat marijuana withdrawal, but participation in an addiction treatment program with a medically supervised detox period can help make the process more comfortable. Healthcare professionals may provide supportive care and medications to ease withdrawal symptoms, such as nausea or headaches. Medications that have shown promise in studies include the sleep aid Ambien, an anti-anxiety drug called BuSpar, and an anti-convulsant drug called gabapentin (Neurontin).14
Current scientific study suggests that a combination of behavioral therapy and medications may be effective in treating marijuana use disorder, particularly in people who also struggle with mental health disorders. Cognitive behavioral therapy, motivational enhancement therapy, and contingency management may all be effective behavioral therapeutic interventions for someone with a mental health disorder and marijuana addiction.14
. National Institute on Drug Abuse. (2018). DrugFacts: Marijuana.
. Drug Enforcement Administration. (2017). Drugs of Abuse.
. Substance Abuse and Mental Health Services Administration. (2017). Key Substance Use and Mental Health Indicators in the United States: Results from the 2017 National Survey on Drug Use and Health.
. National Institute on Drug Abuse. (2018). What are marijuana effects?
. Redwood Toxicology Laboratory. Marijuana Drug Information.
. Verstraete, A. (2004). Detection Times of Drugs of Abuse in Blood, Urine, and Oral Fluid. Therapeutic Drug Monitoring, 26(2).
. Redwood Toxicology Laboratory. (2014). Laboratory Testing Reference Guide.
. MethOIDE. Biological Tests.
. Taylor, M. et al. (2017). Comparison of cannabinoids in hair with self-reported cannabis consumption in heavy, light and non-cannabis users. Drug and Alcohol Review, 36(2), 220-226.
. Columbia University: Go Ask Alice. (2018). Marijuana and drug detox kits.
. Mittal, M., Kalia, R., and Khan, A. (2011). A Case of Psychosis After Use of a Detoxification Kit and a Review of Techniques, Risks, and Regulations Associated With the Subversion of Urine Drug Tests. The Primary Care Companion, 13(5).
. National Institute on Drug Abuse. (2018). Is marijuana addictive?
. American Psychiatric Association. (2013). Diagnostic and statistical manual of mental disorders (5th ed.). Arlington, VA: American Psychiatric Publishing.
. National Institute on Drug Abuse. (2018). Available Treatments for Marijuana Use Disorders.