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Everything You Need to Know About a Marijuana Drug Test

Nothing screams marijuana drug tests more than college students necking cranberry juice hoping to flush it out of their system.  

But now recreational marijuana is getting legalized in more states, where do marijuana drug tests lie?

Don’t worry, we’ve got this covered.  Read on to understand how marijuana drug tests work.

First, What’s the Law?

A number of states have active medical marijuana laws and adults can use marijuana legally in 11 states including Washington, DC, the Northern Mariana Islands, and Guam.

Here, the federal government classifies marijuana as a Schedule I controlled substance.  The FDA hasn’t approved medical marijuana for a medical indication but it is often prescribed for chronic pain, nausea, HIV, glaucoma, and IBS (irritable bowel syndrome).

How Long Does Marijuana Stay In Your System?

Before you Google “how long does marijuana stay in your system?”, know that even though the effects of marijuana fade quickly, the drug can be detected in the body for weeks later.

It can range from a few hours to 90 days to break down the weed in your system depending on how often or how much weed the person has used. 

To calculate it, know the half-life of marijuana is how long it takes for half of the drug to be metabolized and eliminated from the bloodstream. 

And note that even though there are different cannabinoids present, it’s THC your employer is trying to find with a cannabis drug test.

Where Can You Find Traces of THC On Your Body?

THC is broken down and modified into metabolites, a type of molecule. There are 80 various metabolites in THC which may have their own effect on your body’s endocannabinoid system.

Some THC metabolites last for 20 hours where others stored in body fat have an elimination half-life of 10 to 13 days.  Overall, it can take five to six half-lives for a substance to completely disappear.

You can find traces in:

Blood and Saliva

Blood tests aren’t usually used as marijuana stays in your bloodstream for a short time.  You can use blood or saliva tests to show current intoxication but unlike blood tests for alcohol consumption, they don’t show a level of intoxication or impairment.


Hair tests can detect marijuana consumption up to three months later but they can’t determine how much marijuana they used.


Urine is famous around the workplace for drug testing.  It only shows recent legal marijuana use and not current intoxication or impairment.

Because of the time required between use and your body breaking down the THC, any traces are eliminated in the urine.

What About False Positive Testing?

There are times when tests produce false positives. 

Workplaces screen the first sample with an immunoassay test and if it’s positive, the sample is screened again with a gas chromatograph-mass spectrometer.

The second process is far more accurate so false positive tests are almost nonexistent.

Factors that Determine Marijuana Detection Time

The length of time marijuana stays in your body depends on:

Frequency of Use

As expected, people who use marijuana regularly have reported positive drug test results after 45 days since use, and those who use more heavily have positive tests up to 90 days after quitting.


Women metabolize THC at a slower rate than men because they have higher levels of body fat.


The quicker you metabolize, the faster traces of marijuana will disappear from your body.  Metabolism depends on various factors like age, physical activity, and certain health conditions.


When you’re dehydrated, you’ll have higher THC concentrations in your body.  But don’t spend the day chugging water, it will only dilute the THC traces, and you may have to re-sit the test.

How You’re Consuming Marijuana

We’re blessed with many ways to enjoy marijuana and these methods determine how well they’ll be detected on a drug test.

If you smoke or vape marijuana, the THC levels will be far lower than if you took an edible.  Edibles take the longest to break down and leave your system.

Getting Marijuana Out of Your System 

Many employers have a zero-tolerance drug policy which can include random drug testing for current employees and new ones.

Note that if you are told to take a urine test but you’ve recently smoked marijuana, you’ll probably fail the test especially if you use it regularly or heavily.

Even though many states have legalized marijuana for recreational use, you can still be fired for failing a drug test.  The only sure-fire way to pass a marijuana test is by withholding marijuana if you feel a test is imminent.

Use Drug Screening Agents

It’s not guaranteed but you can buy herbal tests that allegedly clean the body’s system of marijuana traces.  But the catch is that most of these agents must be used over an extended period of time, where the body will naturally eliminate THC.

Tampering With a Test

If you’re desperate, you can contaminate a urine sample so no traces of THC are found.  Many companies even sell products as urine test adulterants but if the laboratory conducts a separate test, they’ll know it’s fake.  It’s important to learn more before taking the risk.   

Now You Know Everything About Marijuana Drug Tests!

Although a marijuana drug test is daunting, it’s important to know the ins-and-outs of them.  It all depends on how much marijuana you’ve consumed, when, how quick your metabolism is, and whether you’ve ingested or smoked it.  

The safest way to pass a drug test, especially at work, is to refrain from using marijuana leading up to it.  Good luck!

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