How Long Does Weed Stay in Your System?

Lick, urine & hair tests – there are many ways to see how long THC stays in your system. Your drug dealer has their own theories, but what does science say?
How Long Does Weed (Marijuana) Stay In Your System?
How Long Does Weed (Marijuana) Stay in Your System?: Photo via Getty (Michael M. Santiago)

Whether you're worried about a drug test at work or getting pulled over on the road, the age-old question – how long does weed stay in your system? – has been a cause of discussion for every stoner and bonghead who’s found themselves in the lulls of a high.

But while your local drug dealer might seem like the go-to for such information because of that one “Totally Real” thing they read on the internet, we’re here to bring you the actual science.  


First things first: Whether you're eating gummies or smoking a joint, the most abundant component of cannabis is a chemical called THC, which in scientific terms stands for delta-9-tetrahydrocannabinol. That chemical will have a brain and body-altering effect. It might make you euphoric, relaxed, giggly or, on the other end of the spectrum, anxious, paranoid and irritable.

Various drug tests can usually detect the amount of THC in the system through metabolites – which is a product made or used when the metabolism breaks down food, chemicals or drugs – and is also dependent on your body’s make-up, whether you smoke or ingest and how often you do it.

How Long is Weed (Cannabis/Marijuana) Detectable via Drug Testing?

There are a number of ways to test for THC and its by-products: through blood, saliva, urine and hair. Each can present chemicals for differing periods of time.

Blood Testing

Blood testing for THC from cannabis has the smallest window of time for accuracy especially if you smoke it. However, traces of THC will hang around longer if you ingest it.

When it comes to smoking, THC levels will rise and peak in the blood within three to 10 minutes. After an hour those levels will decline about 90 per cent. The speed that it decreases will depend on how much you smoke and your body’s make-up, but the generally accepted time frame that THC can be detected in the blood is three to four 4 hours after. However, a study in 2009, found that a daily user still had THC in the blood after six days of abstinence. 


Edibles on the other hand are said to hang around in the blood for one to two days. Some sources even say that it could be up to three to four days. The reason for the longer lingering is because edibles need to be processed through the digestive system, meaning that it takes longer to process the marijuana metabolites, whereas smoking a joint instantaneously affects the body through the lungs and therefore wears off quicker. 

Saliva Testing

THC and metabolites can appear in oral fluid by “passive diffusion” from the blood, but it also can be deposited in the mouth when smoked. 

A saliva drug testing kit or lick test uses a biochemical process known as enzyme immunoassay to detect THC in your system.

A recent study found that saliva testing can detect how long weed stays in your system for up to three days (72 hours) after use. For a frequent or heavy user, that number can double.  

However, according to the Australian Alcohol and Drug Foundation (ADF), roadside marijuana saliva tests can only detect THC for around 12 hours after use in people who use cannabis infrequently, and 30 hours for people who use it frequently.

Lick tests have become one of the most commonly used methods because it can detect weed use just minutes or hours after smoking. But recent studies suggest  they are inconsistent in predicting the level of intoxication and impairment of a person and also regularly produce false positives.


Urine Testing

When you ingest marijuana, the liver breaks it down into metabolites. 20 per cent of those leave the body through urine, the other 80 per cent leave through faeces. 

On average, marijuana urine tests can detect THC between three and seven days. However, that can change depending on how regularly you smoke or ingest it. For someone who uses cannabis at least once a day, weed urine tests can detect THC anywhere from 14 to 90 days from use. For a moderate user (which means three times a week) it may be detectable anywhere from five to seven days. For a one-time user, it’s one to three days.

The reason why THC stays in the system of chronic users so long is because it builds up in the body and can only break down at a specific rate relative to your genetics. The extra THC will be stored in your fat cells and be slowly released.

Hair Testing

Depending on the length of the hair it can range anywhere from one week to one year. But, like always, results are heavily reliant on the dose of cannabis ingested or smoked. 

“​​Hair [tests] can be used, but [those tests are] less reliable and more expensive,” Jordan Tishler told VICE, an instructor at Harvard Medical School and president of the medical cannabis practice InhaleMD

“They also can detect the presence of cannabis and other substances the longest—about three months.” 


But how does weed get in the hair in the first place? I’m glad you asked. When you ingest or smoke weed, THC will enter the bloodstream, make its way to cannabinoid receptors in the body’s cells and bind to them. On the way, a few cheeky ones will enter the blood vessels that feed the cells in the scalp. Through the hair papilla, THC enters the area where the actual hair grows and from the root, sprout upwards, carrying THC into the hair follicle matrix.

However, according to Quest Diagnostics, a premier drug testing lab in the United States, it can take up to 10 days before a hair’s root (that contains THC) can be pushed out of the scalp and into the hands of testers. If you’ve got hair that grows at about an average rate of 1.3cm a month, the sample that they’d take would reach back about three months. But as stated before, if a longer piece of hair is tested it could go back years.

Interesting side fact: the more pigmented the hair the more a drug will bind to it – sorry fellow brunettes. 

What Factors Affect How Long Weed Stays In Your System?

The reason why the time frames between how long THC stays in the system and when it disappears differ so much person-to-person depend on a wide range of factors: the dosage and frequency of use, how much THC is in your weed, the way you consume it, the make-up of your body (i.e. your metabolism rate and excretion route), your gender, hydration levels, body mass index, your overall diet and lifestyle and, finally, your genetics.

It’s a complex matrix of external and internal variables.


How Do You Get Geed Out Of Your System The Fastest?

There is a general lack of resources behind whether there is any way to detox or metabolise THC in the body quicker. However, some reports will tell you drinking lots of water, exercising (because a lack of fat cells means less storage for cannabinoids) and taking various detox agents could help if you have a drug test coming up. 

“There are some commercial products designed to help cheat, but since these are illegal, there’s no testing to show that they work,” said Tishler.

“There is no regulation to protect consumers against such products. Most are ‘proprietary,’ and do not list their ingredients. Further, there are no safety or efficacy tests done on them, so the real answer is we have no idea if they work, or are safe.” 

Further research suggests that the age old myth that exercise will help for a quick detox are false. In 2014, a study published in Basic and Clinical Pharmacology, tested whether exercise or food deprivation would increase or decrease THC in urine. Six chronic and daily cannabis users were exposed to a 45-minute moderate-intensity workout and 24-hours of no food. Long story short, they concluded that neither exercise nor fasting made a noticeable change to the cannabinoid concentration that would hamper the interpretation of drug tests. In fact, a study from 2013 found that exercise could actually increase THC levels for a short period of time because of the release of dormant THC in the fat cells. 


If we’re talking about using fluids to detox THC for a urine test in a short amount of time, it’s likely that you could, in fact, dilute THC with large amounts of water, however, since this also has the potential to dilute enzymes that naturally occur in urine, if the sample is too diluted it could be flagged as suspicious or unacceptable. 

“There are many ways to cheat urine drug screens, but most screening programs are wise to these,” said Tishler.

The takeaway here is that abstinence, regular exercise and a healthy diet is really the only way to help remove THC in the system over time. It also relies on your body’s individual metabolic rate. So all-in-all there is no scientifically proven same-day detox method – sorry.

How Long Does It Take To Feel The Effects Of Weed? 

How long it takes for the THC in cannabis to enter the system and produce its mind-altering effects depends on any number of things: how strong the strain is, whether you smoke or consume edibles and how high your tolerance is.

Generally, the effects of smoking or vaping can kick in from two to 10 minutes and last for two to eight hours. Ingesting it takes a bit longer as it needs to be broken down by digestive processes, so it could kick in anywhere from 30 minutes to an hour (sometimes up to two) and last for three to nine hours (this is also dependent on stomach contents). 


How Long Does The High Of Weed Last?

Everyone’s high is different and there are a list of factors that come into play when determining the length of your high, including:

  • How much you ingest
  • How you consume it
  • The amount of THC in it
  • Your body weight & metabolism
  • If you’ve eaten or not
  • Your tolerance level

All of these factors combined play an important in establishing how much of a lasting high you’ll have.

If you’re smoking cannabis, your high will typically last around 1-4 hours. If you’re eating an edible, the effects may not be felt for up to 2 hours, but the high can last anywhere between 4 and 12 hours (and sometimes, you’ll feel the effects for up to 24 hours). If your method of choice is dabbing, your high will peak almost immediately, and could last anywhere between 1 and 3 hours.

Human’s are creatively and intellectually complex, as are our methods of getting high. So while there is no finite answer to the length of a “general” high, there’s a plethora of answers for the length of a high through various different processes.


Whether you’re a beginner (side note: take a look at these tips on weed etiquette) or a certified stoner trying to quit or just someone trying to dodge a drug-test, there is no one size fits all. The period for how long weed will stay in your system will differ from one person to the next. But just to be safe, probably don’t operate heavy machinery just after a toke, or expect to pass any type of test when you’ve eaten a cookie the night before, or drink 20-litres of water trying to flush the THC from your system. 

The weed will still be there even though the high may not.

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