How Long Does Marijuana Stay In Your Hair

Calculate The Duration Time Of Detectable Chemicals For Marijuana in Hair From Last Use:

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Light Occasional User
Regular User
Chronic User

in Hair


Why Does Marijuana Stay in your System?

Marijuana once smoked does not have very long lasting effects but it has an active ingredient tetrahydrocannabinol (THC) which stays in your system for a really long time, in some cases even months. What decides if this ingredient is going to stay in your system for longer isn’t the process by which it is metabolized. In general when marijuana is smoked or consumed orally, it is retained in the body for 1-5 days. For regular users who tend to smoke weed, it is almost impossible to get it out of the system and for the drug test to reach a zero level it could take months from the date of consumption in the hair follicles.

The half-life of the tetrahydrocannabinol is about 20 hours, but this is heavily influenced by several factors like frequency of consumption, weight etc. another factor that plays a major role in deciding how long does marijuana stay in your hair is the potency of the pot smoked. This along with other factors like metabolism rate and health decides how long your body retains its constituents.


So, How Long Does Marijuana Stay in your Hair?

A hair follicle test is found to be way more effective than a urine test and this is all because the detectable chemical of marijuana (THC) stays in your hair for a very long time. So to answer your question directly of how long does marijuana stay in your hair, we’ll at least for a couple of months, and up to 90 days for regular chronic users. If your 2 years old hair strands are still present and you did use marijuana back then, it can still be detected.

Apart from the hair test, THC or tetrahydrocannabinol can show up in other tests for around 3-10 days of last use. There is a loophole to this test because of which it is not considered to be an ideal test for detection of drug usage and that is the fact that THC doesn’t necessarily bind to the hair follicle and this method definitely trumps the urine test by all means possible. There is a valid reason for this. During the time marijuana was consumed all the hair strands that were present or growing at that point of time will help the test results to turn out as positive. It simply doesn’t matter how many months back you smoked because to answer how long does marijuana stay in your hair you would have to consider several other factors out of which the most important one is whether you retain the hair strands that were growing at that point of time till the time you are tested or not. Not only this, but it could also help detect how much drug was used.


Will you Retain Marijuana in your System if you Smoke Just Once?

So, you might feel that you won’t test positive if you have just smoked it once. This is not necessarily true, as because with 1-5 days of smoking pot or using a vaporizer you might test positive for it. Now there is a significant difference between people who smoke regularly and those who don’t. If you’re one of the regulars who just can’t do without pot then you might test positive even after a week from the last day of consumption.


How Accurate is the THC Hair Test?

A study published in 1995 by the Journal of Analytical Toxicology was conducted to test the presence of cannabis in human hair. This study showed that out of all the 16 cannabinoids that can be extracted from cannabis, THC (tetrahydrocannabinol), CBD (cannabidiol) and CBN (cannabinol) could be isolated at that same point of time. A total of 30 hair samples were tested. (See table 1 below)
How Long Does Cannabis Stay In Your Hair
The findings on this table clearly show that 23 of them tested positive for CBD, 5 for THC and 22 times for CBN. This means that although the THC method of hair testing is used by many organizations, it is the least effective method of detecting cannabis than CBD, and CBN testing methods. It’s also important to note that both CBD and CBN have a lower concentration range of detection compared to THC, which maybe the reason for why these tests have greater abilities for detection.

THC Drug TestAnother study published in 2007 by the Forensic Science International which aimed to study the deposition of the marijuana contents in hair after long term use of it. The results showed the presence of THC, CBN and CBD in the subjects that used cannabis before and were absent in those who didn’t. This was all based on the hair-strand test. The results also indicated a significant increase in the amount of cannabinoids retained in the hair with increase in the dosage. It concluded that it would be far better to consider the sum of all the cannabinoids present in the hair rather than just testing for THC. So basically, a hair test for cannabinoids can be far more accurate than a THC. However, most drug tests look to detect THC, which can also remain datable for a long time in the hair of a regular cannabis addict.

Both of these studies goes to show how long does marijuana stay in your hair and suggests that cannabinoids in human hair can be present for a very long time and varies according to a few factors. These also suggest that a combined test might have more potential to turn out as positive rather than just testing for THC.

On the whole, looking at the evidence in case studies. The THC hair test isn’t the most accurate method for testing as cannabidiol and cannabinol, however most cannabis hair tests only look for THC components in the hair follicle, which still none the less has a reasonable rate of accuracy. To learn more about How Long Does Marijuana Stay In Your System, click here!



Cannabinoids in hair after long term use – Forensic Science International Journal – 2007 – By Gisela Skopp, Peter Strohbeck-Kuehner, Karl Mann


Testing Human Hair for Cannabis – Journal of Analytical Toxicology – 1995 – By V. Cirimele, H. Sachs, P. Kintz, and P. Mangin