How Long Does It Take To Clear Weed From Urine

How Long Does One Hit Of Weed Stay In Your System? (2021 Edition)

How long one hit of weed stays in your system after a single toke is not as straight forward as you may want it to be. But for starters, it is safe to go with the 7 day rule for a single hit. This article explains why the 7 day rule may adjust upwards or downwards based on some key factors.

The 7 day rule

You have probably heard that weed takes between 5-7 days to clear out of your system. This is very close to the truth, because it brings to light a very important physiological consideration by the name of half life.

The half life of THC affects how long one hit of weed stays in your body.

The half life of a drug is the amount of time it takes for 50% of that compound to be eliminated from the body. It takes about five half lives for a compound to be reduced to undetectable levels in the body.

Tetrahydrocannabinol (THC) is the poster child of marijuana, though CBD is fast advancing towards this spot. THC is the compound that is responsible for the typical marijuana high, it also happens to be the compound that is screened for in standard drug tests.

The half life of THC for a social smoker is around 32 hours, while that of a chronic smoker is between 5-10 days. Therefore for the occasional user, it would take 160 hours for THC to be completely eliminated from their bodies. For a daily smoker, this could as well translate to close to two months.

Chemical structure of THC which has a half life of 24h-32h. Half life is a key determinant for how long one hit of weed lasts.

Half life is affected by many factors including one's metabolism rate and kidney function. But generally speaking, half life is a pivotal pointer in determining how long one hit of weed will stay in your system. So with this, we can conclude that a one week duration should be sufficient to clear one hit of THC from your system.

Aside from that, other variables also come into play.

Factors that influence how long one hit of weed stays in your system:

1. Age

THC metabolites are excreted through the kidneys primarily. Other channels of excreting THC include saliva, sweat and exhalation.

As you age, a few of your body's physiological functions begin to diminish. The renal tubules that are responsible for urine formation may slow down with age. This means that you will not be able to create and excrete urine as fast as you normally would. What this translates to is an increased half life of THC in elderly persons. Decline in hepatic function in the elderly also contributes to a prolonged half life of THC. With these changes, a hit of weed will stay longer in the body of an elderly person compared to that of a younger person.

An older person will take a longer time to eliminate a single hit of weed from their system.

2. Body Fat Percentage

THC is lipohyllic meaning that it binds to fat more readily than it binds to water. In the body, THC is taken up from the bloodstream into the heart from where it finds its way into fat cells around the body. When THC is exhausted in the bloodstream, the fat cells are broken down to release the THC that they are holding.

People with greater body fat percentage will have more surface area for THC to bind to, meaning that they will hold onto more THC than their thinner counterparts. It also follows that people with greater total body fat percentage may take longer to clear out THC from their systems after taking a hit of weed.

3. Smoking frequency

As alluded to earlier, smoking frequency will have an impact on the plasma half life of THC. People who smoke frequently end up accumulating residual THC metabolites in their fat cells. This will take longer to get rid of over time. Putting it into perspective, this is how the difference looks like:

One-time users:

THC in saliva: lasts up to 24 hours
THC in blood: lasts up to 3 days
THC in hair: may not be detected

Regular users:

THC in saliva: lasts up to 24 hours
THC in blood: lasts up to 10 days
THC in hair: lasts over 3 months

Heavy users:

THC in saliva: lasts up to 24 hours
THC in blood: lasts up to 35 days
THC in hair: lasts over 3 months

THC concentration

A study conducted in 2007 by the National Institute on Drug Abuse examined how long weed stays in the system of non-regular smokers taking different dosages of weed. One group was given high dose THC while the other was given low dose THC. The group given a higher dose took longer to eliminate the weed. This means that one hit of weed may take longer to exit from your system if you consume a higher THC dose.

Dabs are usually highly concentrated and affect how long one hit of weed lasts in your body.

Weekly cardio level

THC and its metabolites are lipohyllic, meaning that they accumulate in fat cells over time. A study conducted by the University of Sydney in 2006 showed that exercise triggers lipolysis. When this happens, stored THC metabolites are released back into the blood stream from where they can be excreted. A person with higher cardio activity level will have a shorter THC half life than a person with less cardio activity level, in spite of a similar total body fat percentage.

Sensitivity of test used

Standard drug test will usually have a 50 ng/ml cutoff for THC and its metabolites in urine. More sensitive tests will detect upto 20 ng/ml of urine. When the later is used, one hit of weed may be detectable in urine for a longer time.

What about Cannabidiol (CBD)?

One hit of weed may contain THC as well as CBD. However, most standard drug testing will not be looking for CBD. That said, the half life of CBD is similar to that of THC, being about 18-32 hours. CBD is lipophyllic as well. This means that the same factors that affect how long THC stays in your system will also affect CBD in a similar way.

Sources

Geriatric Physical Therapy (2012): Geriatric Pharmacology. Retrieved from https://www.sciencedirect.com/book/9780323029483/geriatric-physical-therapy
XPharm (2007): The Comprehensive Pharmacology Reference. Retrieved from Decline in hepatic function as one ageshttps://www.sciencedirect.com/referencework/9780080552323/xpharm-the-comprehensive-pharmacology-reference
Journal of Addiction, Research and Therapy (2016): Pharmacology of Marijuana. Retrieved from https://www.omicsonline.org/open-access/pharmacology-of-marijuana-2155-6105-S11-012.php?aid=84733BJP (2009): Reintoxication: the release of fat-stored Δ⁹-tetrahydrocannabinol (THC) into blood is enhanced by food deprivation or ACTH exposure. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2782342/
Mayo Clinic Laboratories: Marijuana THC. Retrieved from https://www.mayocliniclabs.com/test-info/drug-book/marijuana.html
PubMed (2006): Exercise Increases Plasma THC Concentrations In Regular Cannabis Users. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/24018317