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How long does cannabis stay in your system?

Depending on consumption method, frequency of use and other variables, cannabis can stay in your system up to 90 days. This article covers the types of tests and explains the research behind cannabis metabolisation.

Key Points
  1. There are many factors that determine how long cannabis can be found in your system.
  2. The saliva or oral fluid test looks for THC and is the test used in Australia during roadside tests.
  3. Saliva tests are known to provide false positives between 5%-10% of the time.

In this short video, Tom Arkell from the Lambert Initiative for Cannabinoid Therapeutics explains how long cannabis stays in your system.

Cannabis/Marijuana in your system

The question of, ‘how long does cannabis stay in your system?’ is one of the most popular cannabis questions in Australia. Upon hearing that, many people think, “That a stoner question,” when in fact it’s not.

The laws regarding cannabis and driving in Australia are outdated and don’t actually accomplish the goals that drug driving regulations are meant to achieve. Cannabis or marijuana, whatever you choose to call it, is actually similar to alcohol in this way. Just because an individual has THC in their system, it does not mean that the individual is impaired. 

Driving with any THC in your system in Australia is illegal. So, it’s important that you understand how long cannabis stays in your system to protect you from being wrongfully accused of driving while impaired.

In this article, you’ll learn everything you need to know about how long cannabis, mainly THC, stays in your system for. If you’d like to jump to a specific section here’s what will be covered:

  1. How long does cannabis stay in your system?
  2. What are the factors that affect cannabis in your system?
  3. Saliva or mouth swab test for cannabis (Method for cannabis roadside / drug driving test)
    1. Can cannabis in pill form be detected by a saliva drug test?
    2. Are roadside mouth swab drug driving tests accurate?
  4. Cannabis drug tests and detection times (infographic)
    1. Blood based drug tests for cannabis
    2. Urine based drug tests for cannabis
    3. Hair follicle drug test for cannabis

How long does cannabis stay in your system?

Some studies suggest that cannabis can be found in your system for up to 90 days.

However, there isn’t really a definitive answer to this question as it depends on a number of individual variables and external factors including the type of test being used to screen for the drug.

Let’s look more closely at some of those factors.

Factors that impact cannabis in your system

How long cannabis stays in your system differs for each person due to a number of factors. The things that can impact the duration of cannabis in your system are:

  • Body fat percentage
  • How often you consume cannabis
  • How much cannabis you consume
  • how much you exercise
  • The type and sensitivity of the drug test.

THC is fat soluble and can build up in your body fat. If you consume cannabis regularly, you may have THC metabolites in your system for an extended period. The more body fat you have the more potential for THC to be stored in your system. 

Interestingly enough, one study shows that exercise can actually increase the amount of THC in your plasma (one part of your blood).

The rest of the factors are actually quite logical. The more regularly you consume cannabis the more likely it is to stay in your system longer. The amount of cannabis also impacts the concentration of cannabinoids in your system. 

For the rest of the article we’ll focus on the types of tests and cannabis drug test detection times.

Cannabis drug tests and detection times

The type of drug test you take will have an impact on how long cannabis can be found in your system. Even the calibration of the drug test being taken matters. We’ve listed the standard test below in the shortest to longest amount of time cannabis can be found. It’s also important to note that saliva can only detect THC and not CBD. So, when explaining how long ingested THC stays in your system, it’s more of an estimate than actual fact.

how long does cannabis stay in your system

Saliva (Method for cannabis roadside / drug driving test)

A mouth swab or oral drug test for cannabis is the method that Australian police use to test for driving impairment. 

How long does cannabis stay in your saliva?

Most research shows that cannabis can be detected in your saliva for up to 24 hours after use, however, a few tests have shown up after 72 hours of use. For chronic users, this could be longer, and smoking is more likely to show up longer than edibles.

In a study conducted at the Lambert Initiative for Cannabinoid Therapeutics in Australia, the team found that most people tested negative three hours after consumption. The group tested was given 13.75 milligrams of vaporised THC flower. 

“THC only gets into saliva in the first place due to contamination of the oral cavity when you consume cannabis. So, it’s only when you use cannabis by smoking, vaporisation, eating or via any other way that it comes into direct contact with your mouth that you’ll actually end up with THC in your saliva.”

Tom Arkell, The Lambert Initiative For Cannabinoid Therapeutics

Can cannabis in pill form be detected by a saliva drug test?

Professor Ian McGregor was quoted saying, “If you take it in a capsule, it will bypass your saliva.”

So, if you have been prescribed cannabis in pill form, you really need to be careful to make sure that you’ve waited a safe period of time before driving.

However, research has consistently shown different results. The general rule of thumb for intermittent consumers is that cannabis can be detected in your saliva for between 24 and 72 hours after use. For chronic consumers or medical patients one study has shown detection of up to 8 days. 

These are guides, not exact science. The time could be longer and smoking is more likely to show up longer than edibles.

Are roadside mouth swab drug driving tests accurate?

Roadside saliva tests have a number of concerning issues.

These tests are screening tests, which means they’re designed to provide a rapid and portable testing solution at the roadside. While these tests are efficient, they come at the expense of precision.

The test only finds what’s trapped in your oral cavity and there are many factors which impact how much THC is in your saliva. It can vary from person to person and factors like the pH of your saliva can contribute to inaccuracies.

A recent study from the Lambert Institute showed that these saliva tests are showing false positives between 5% to 10% of the time.

Blood based drug tests for cannabis

How long does cannabis stay in your blood?

The method of consumption plays a big part in how long THC can be detected in your blood.

Research shows that, when inhaled, THC is rapidly absorbed and reaches its highest concentration in your blood within the first three to ten minutes.

The same research showed that when consuming cannabis in an edible (or oil), peak THC plasma levels were achieved around one to two hours and in some cases even longer.

Blood tests for cannabis, as with other methods, will depend on the frequency of consumption. A study from 2009 also showed cannabis could be found for up to 6 days after last consumption in daily consumers.

While there is no definitive answer, the general rules are as follows:

  • For individuals who consume cannabis intermittently, cannabis can stay in your blood for up to 24 hours. 
  • For frequent or regular consumers, cannabis can stay in your blood for up to 72 hours.
  • Cannabis has been found in blood for up to 6 days.

Blood is not a strong indicator of intoxication.

Urine based drug tests for cannabis

As with the other methods of testing mentioned, research on cannabis in urine tests varies. However, the urine test is the most common method of drug testing, particularly in the workplace.

How long does it take for cannabis to leave your system for a urine test?

Before THC is excreted through the urine, it is broken down into many different chemicals or metabolites. Urine tests can detect THC-COOH, a metabolite of THC for up to and exceeding 30 days. A 2017 study by the Mayo Clinic’s gives the following breakdown:

  • Occasional users (up to three times a week): 3 days
  • Moderate users (four times a week): 5 to 7 days
  • Chronic users (daily): 10 to 15 days
  • Chronic heavy users (multiple times a day): more than 30 days

Hair drug tests for cannabis

How long does cannabis stay in your hair?

Hair tests can capture drug use for the longest time of any test. Hair tests are also the most contested due to the inaccuracies/contamination factors.

Research has shown that cannabis can be detected in hair for about 3 months (90 days). Since hair grows approximately 1.3cm per month, a 4cm hair removed from close to the scalp can potentially provide a window of cannabis use for the past three months or 90 days.

One challenge with testing the hair is that studies show that you can be tested positive for cannabis via hair from second hand smoke. So, while hair can show a history of drug use, it can also show results that aren’t a true representation of one’s cannabis use.

Another issue is that a study conducted in 2015 showed that hair follicle drug testing correctly identified only 52.3 percent of people who reported recent marijuana use.

Conclusion

Unfortunately there isn’t really a definitive answer for how long cannabis takes to leave your system. With all cannabis drug testing it will depend on a number of factors that are unique to you. 

If you consume cannabis regularly, cannabis will likely stay in your system for longer than if you’re an intermittent or once off consumer.

The one thing that science has proven in this space is that there are certain windows of time you should know about but nothing fool proof. 

If you’re using cannabis as a medicine and need to drive regularly then be mindful that having any THC in your system is illegal. In that case, a CBD product might be best for you. 

If you know that you’ll need a drug test shortly or in the future, it’s going to be best to understand the how the tests work and exactly what the test is looking for. If it’s for an employer and you have a medical cannabis prescription, learn about your employment/drug testing policies and it may be best to talk to your employer in advance.

Information

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Tom Arkell

Thomas Arkell is a psychopharmacologist with a background in psychology and philosophy. He has a fascination with all things cannabis and a broad interest in how psychoactive drugs affect human behaviour and cognition and our experience of the world around us.

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Tom Brown

Tom is a co-founder of honahlee, startup junkie, a cannabis enthusiast and a digital marketer. His interest in cannabis began as a teenager growing up in New York. Tom loves to trawl through cannabis research, documenting cannabis truths and myths. He started honahlee to help reduce the stigma around cannabis in Australia by educating people about the many uses of the plant.

Disclaimer

Please note, the team at honahlee are not doctors. It’s important to know that neither honahlee nor Tom Arkell are recommending that anyone uses marijuana for medical or recreational purposes. Cannabis is a drug and may have negative side effects. Medical cannabis in Australia is regulated by the Therapeutic Goods Administration and details about cannabis as a scheduled drug can be found on their website. Please consult with your doctor to find out if cannabis is right for you.