How Long Does Marijuana Stay in Your System?

How long does marijuana stay in your system? Tests for cannabis can detect THC anywhere from a matter of hours to several months after last use. It depends on the individual, how often they partake, and the type of testing method.

Last Edited:

01/02/2022

Clinically Reviewed:

10/07/2021

Medical Reviewer:

Dr. Tasnova Malek

Cannabis isn’t going anywhere.

An estimated 12% of U.S. adults have told pollsters that they smoke marijuana. Those who are lighting up (or vaping or munching edibles) vary, however.

  • More than one out of every five people ages 18 to 29 light up. That’s twice as high as ages 30-64 and seven times higher than adults over 65.
  • Liberals use marijuana at a much higher rate, too. Nearly one out of every four smokes the stuff, compared to 4% of conservatives and 12% of moderates.
  • Men are more likely to smoke it (15% compared to 9%).

One 2017 poll found 52% of American adults have tried marijuana at some point in their lives.

Despite it being classified as a Schedule I drug—deemed by federal authorities as having no accepted medical purpose and a strong potential for abuse, a classification cannabis shares with heroin, LSD, and ecstasy—use has never really died back.

In recent years, in fact, more than half of all U.S. states have made cannabis use legal in some capacity, be it recreational or medicinal.

Legalization allows it to be better regulated, a move that advocates say makes it safer for all.

That’s in part because today’s cannabis strains are much more potent than strains of just 25 to 30 years ago. There’s much more delta-9-tetrahydrocannabinol (THC), the main psychoactive ingredient, in marijuana these days. Often there is less cannabidiol (CBD), which doesn’t produce the high that THC does, but it can help with pain, anxiety, seizures, and a number of other conditions.

Many strains have such a wide THC-to-CBD ratio that they lose the tempering of THC’s psychoactive effects, which many critics fear may cause issues for people at risk of psychotic illnesses. Regulation and oversight could restore that balance.

Does Marijuana Show Up in a Drug Test?

Cannabis, a hallucinogen definitely shows up in drug tests. The type of test—urine, saliva, blood, and hair are four methods, though urine is most common—will determine how long it can be detected in the system. Whether it’s smoked or ingested can make a difference, too. Other factors that may affect results include the strength of the cannabis and whether a person uses it regularly or not.

Because marijuana is one of the most-used drugs (and legal in many places, to varying degrees), it tends to be screened for the most.

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How Long Does Marijuana Stay In Your System

Generally, cannabis lingers longest in hair, and that’s followed by urine, sweat, saliva, and blood.

When hair follicles are tested for drug use, labs usually look for signs of use in the last 90 days.

Hair grows about a half inch every month, so a 1.5-inch segment of hair taken from close to the scalp can determine if a person has used cannabis in the last three months.

How Long is Marijuana Detectable in Urine?

Testing urine for marijuana (or other drugs) is the most common way to do it. A person who tests positive for THC and other metabolites could have used anywhere within the last three to 30 days. That’s a wide range, but it will hinge in large part on how frequently a person uses it.

Marijuana drug test detection times, after last use, include:

  • Single use: 1.5 to 3 days
  • Moderate use (typically up to four times a week): Approximately 5 to 7 days
  • Heavy (daily) use: 10 to 15 days
  • Chronic heavy use: Up to 30 days, and maybe longer

How Long Does Marijuana Last in Your Saliva?

In the saliva of a casual user, cannabis usually can be detected anywhere from five to 48 hours. Someone who uses it occasionally may test positive anywhere from one to three days. A frequent user may test positive anywhere from one to 29 days.

How Long Does Marijuana Stay in Your Blood?

Marijuana drug tests can detect THC and related compounds in the blood, usually one to two days after last use. Someone who uses it chronically may have cannabis turn up in a screening for nearly a month. Marijuana can be detected in the bloodstream seconds after inhaling.

A number of factors will determine just how long cannabis stays in a person’s system:

  • Body-Mass Index (BMI): The higher a person’s body fat percentage, the longer THC will be detected. That’s because it hides in fat cells. A person’s metabolism will affect how long cannabis lingers in a person’s body, too.
  • Gender: Women metabolize THC at a slower rate than men do. Women usually have higher levels of body fat, providing a storage space.
  • Frequency of use: A casual or one-time user will test clean far sooner than a habitual user.
  • Dosage and potency: The higher the amount of THC in marijuana or the more a person consumes or smokes, the longer it sticks around for screening detection.

Ingested marijuana (edibles, etc.) also tend to linger in a person’s system longer than when it’s smoked or vaped.

  • The test itself. Some tests are more sensitive and can produce a positive result more readily.
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Marijuana Half-Life

The half-life of a drug means the amount of time it takes for half of the drug in question to be metabolized and leave the bloodstream.

The THC in marijuana gets broken down into metabolites, an end-product of metabolic processes. They may affect our bodies’ endocannabinoid systems, which keep the body operating in homeostasis (basically, the nervous system keeps all things humming along). They factor into appetite, digestion, sleep, mood, motor control, pain, pleasure and reward, and more.

Some of THC’s metabolites have a half-life of about 20 hours, but others can last from approximately ten days to two weeks. Most substances require five or six half-lives to mostly leave the system.

Some people may try to cheat a test by drinking a lot of water. If urine looks too pale and clear, labs see it as a red flag that someone is trying to flush the kidneys, and they may request further testing. Taking B vitamins to add a yellow hue to urine doesn’t always work either.

Still, kits are sold online, and advice is plentiful on how to beat a test. Some people use everyday household items like vinegar or baking soda to help pass a screening. Most labs can easily detect these add-ins, so it’s not worth the effort.

The internet and drug stores have plenty of options, usually labeled as detoxes or cleanses. They may have a mix of herbs or other substances, but they’re not regulated by the FDA. In some cases, what’s on the label may not be what’s in the teas or pills.

In truth, the best guarantee for a negative result is to simply not use cannabis.

Sources

  1. news.gallup.com – What Percentage of Americans Smoke Marijuana?
  2. nbcnews.com – New Poll Finds Majority of Americans Have Smoked Marijuana
  3. dea.gov – Drug Scheduling
  4. drugabuse.gov – Marijuana Drug Facts
  5. vice.com – Weed Is Way Stronger Than It Used to Be. That’s Why It Shouldn’t Be Legal
  6. semanticscholar.org – Detection Times of Drugs of Abuse in Blood, Urine, and Oral Fluid
  7. mayoclinicproceedings.org – Clinical Interpretation of Urine Drug Tests
  8. ncbi.nlm.nih.gov – Current Knowledge on Cannabinoids in Oral Fluid
  9. drugabuse.gov – How does marijuana produce its effects?

Medical disclaimer:

Sunshine Behavioral Health strives to help people who are facing substance abuse, addiction, mental health disorders, or a combination of these conditions. It does this by providing compassionate care and evidence-based content that addresses health, treatment, and recovery.

Licensed medical professionals review material we publish on our site. The material is not a substitute for qualified medical diagnoses, treatment, or advice. It should not be used to replace the suggestions of your personal physician or other health care professionals.

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