How Long Does Weed Stay In Your Hair?


How Long Does Weed Stay In Your Hair?

How Long Drugs Stay In Your Blood

How Long Drugs Stay In Your Blood

According to a recent Quest Diagnostics survey, 50% of all drug test positives are for marijuana.

This makes marijuana users the most-frequently targeted drug users in the world.

Which is really ironic, since natural weed is the least dangerous of all illicit drugs.

Even worse, marijuana remains in your system a long time – far longer than any other drug.

But exactly how long does weed stay in your body?

If you are facing a drug test soon, this is an important thing to know.

If you’re facing a hair drug test, then it’s by far the most important thing you need to know, because hair drug tests can detect marijuana use as far back as a year!

This page walks you through the answer to this question, based on scientific facts – not urban legend.

If you have any questions or corrections, please post a comment below.

I check comments about once a week.

Drug Test Detection Times for Marijuana

How far back in time can drug tests detect your marijuana use?

Here is a table that lists reliable detection periods for each type of drug test:

Drug Test Detection Times for Marijuana THC

NOTE: These are just averages, and your experience may vary.

Detection time depends on the kind of test used and the sensitivity of the test process and equipment used (they aren’t all the same).

Other factors that affect the accuracy of a drug test for marijuana include:

  • the frequency of use
  • the dosage/concentration of THC
  • the last date/time of use
  • the user’s metabolism (but not as much as people think)
  • the user’s digestive system (if ingested).

How Fast Does THC Leaves Your Blood, Over Time?

The following chart illustrates the results of two studies that measured the amount of THC and THC metabolite (THC-COOH) in the blood streams of a large number of marijuana users, over an extended period of time.

It shows how blood levels of THC and the metabolite decay, or dissipate, over time depending on whether you smoked or ate your weed/hash.

Please note that this chart displays the average blood levels for a group of people. Each test subject used a different amount of marijuana, and your chart would look different depending on how much and how frequently you used, etc.

Decay in blood levels of THC and metabolites over time

Decay in blood levels of THC and THC-COOH over time

What is interesting about this chart is that it shows:

  • if you smoke weed, your THC blood level will spike quickly then drop below the typical drug test threshold of 50 ng/mL
  • if you eat hash brownies, THC will gradually build over time, peaking at about 4 hours
  • THC-COOH, the metabolite used to detect marijuana use in most drug tests, takes a LOT longer to dissipate.


Hair Test for Weed: How Long Does THC Stay In My Hair?

The hair drug test was developed to identify long-term use rather than one-time or infrequent use.

Hair follicle drug tests can detect marijuana use beginning around 7-10 days after first use.

To do this, test labs use mass spectroscopy and other methods to detect the presence of a non-psychoactive byproduct of THC, a metabolite called THC-COOH. 

The cutoff level that most tests consider a positive result for marijuana use is a concentration of TCH-COOH of 50 ng/mL or higher, in your blood.

One time and infrequent users of marijuana are much less likely to be detected by a hair follicle test.

A 2006 Forensic Science International study, Cannabinoid Concentrations in Hair from Documented Cannabis Users, found that 85% of daily users tested positive for THC use, but only 52% of smokers who used 1-5 times per week were detected.

Eating or ingesting THC also lowers your chance of being detected vs. smoking the same amount of THC.

To learn more about the hair drug test, check out our home page.

Learn More About The Hair Drug Test >>



Urine Tests For Marijuana: How Long Does a Pee Test Detect THC?

The most popular kind of THC drug test is the urine test.  

Because THC-COOH takes such a long time to eliminate from your body, urine tests are more sensitive to marijuana than other commonly used drugs. This is why urine tests are the preferred test for detecting recent marijuana use.

Like hair tests, urine tests look for the metabolite THC-COOH, usually with a cutoff of 50 ng/mL.  Urine tests can detect marijuana for days or weeks after use. They can detect marijuana use for days after the high is gone, even in 1-time users.

The following chart shows the results of a recent study of 1-time users of THC.

Urine levels of THC-COOH for one-time and infrequent users

Urine levels of THC-COOH for one-time users of a standard NIDA cigarette 
Source: M Huestis, Mitchell and E Cone, “Urinary Excretion Profiles of 11-Nor-9-Carboxy-Delta-9-Tetrahydrocannabinol in Humans after Single Smoked Doses of Marijuana,” Journal of Analytical Toxicology, Vol 20:441-52 (Oct 1996).

The most striking thing about this study is how variable the results are – from person to person, and from hour to hour for the same person.

Note that it took Subject B two days to get clean. Subject E was safe the entire time.  Depending on the time of day, Subject G might have passed or failed the 50 ng/mL cutoff.

The reason for this variability is that the concentration of THC-COOH in your urine is highly subject to the amount of water in your body (and urine) and your body’s metabolism.  If you are poorly hydrated or have a low metabolism, you are more at-risk of failing the urine test.

The bottom-line for the urine test is: to be safe, you should assume you will fail if you use any amount of marijuana within a few days of the test.


Blood Tests For THC

A blood test is the most accurate form of marijuana drug test, because it measures the direct presence of THC (delta-9-tetrahydrocannabinol) in your system.

But blood tests only detect drug use back a few days, so they are primarily used in the investigation of accidents and crimes committed under the influence and for spot-testing employees in jobs and professions where any amount of drug influence could be catastrophic.

Blood tests are also ordered in domestic dispute and parole situations, where the court has required abstinence.


Saliva Tests for Weed

In general, saliva tests are not used  to detect marijuana use in the US due to unreliable results.

The main problems with saliva testing for THC, as reported by a large-scale 2006 industry research project, the Rosita Project, include:

  • difficult to obtain enough saliva
  • malfunctioning of devices that read the results

It’s possible, perhaps likely, that the test device manufacturers will continue improving their methods and technologies.


Detection Times for Alcohol and Other Drugs

Urine Drug Test and Hair Drug Test Cutoff Levels and Detection Times


Hair Tests For Alcohol

In the testing industry, the accuracy of the hair drug test for detecting alcohol use or abstinence is hotly debated. In short, the problem is that many common cosmetic procedures can alter the amounts of alcohol-related chemicals that the hair test is looking for.

The hair drug test detects two byproducts of alcohol in the hair follicle, including:

  1. Ethyl glucuronide (EtG)
  2. Fatty acid ethyl esters (FAEEs) including ethyl myristate, ethyl palmitate, ethyl oleate and ethyl stearate

The hair test is not as reliable for alcohol detection as it is for other drugs, because cosmetic treatments can dramatically affect the levels of EtG and FAEEs in your hair. This includes hair straightening, dyeing, bleaching and perming.

In addition, hair products that contain ethanol, such as hairsprays or hair lotions, will affect FAEE levels, though not EtG.

A 2014 survey of 31 test labs held by the Society of Hair Testing concluded that a hair drug test is not, by itself, a reliable indicator of abstinence or excessive consumption of alcohol.

To quote their conclusion:

“It is not advisable to use the results of hair testing for alcohol markers in isolation; all relevant factors surrounding a case must be considered when providing expert interpretation and opinion.”

In other words, the accuracy of the hair test for alcohol is considered unreliable if cosmetic activities are not accounted for.

If you think you may test positive for alcohol use, then you may want to use an aggressive cosmetic treatment or an aggressive hair cleaning regimen like the Macujo method.

Learn More About The Macujo Method >>


and now we wait for our marijuana drug test




  1. Kelcey
    April 18, 2016 @ 6:39 pm

    I have a test in exactly one week. I smoked weed on 3 separate occasions 6 months ago. Before that it had been 2 years. My hair has grown out over an inch and a half since I did it and I’ve also bleached my hair since then. What do you think my chances are of passing the test


    • Jay Z.
      April 24, 2016 @ 1:27 pm

      I think your chances of passing are quite good.


    • ty
      March 3, 2017 @ 1:59 am

      curious, did you end up passing this?


  2. Braden
    May 31, 2016 @ 12:11 am

    I smoked about 2 grams 7 days ago and it was my first time would they be able to detect in a hair test of its my first time in 8 days ?


    • Jay Z.
      June 1, 2016 @ 4:35 pm


      Yes, it’s possible. But highly unlikely.

      Best of luck,



      • Mike
        June 14, 2016 @ 10:06 pm

        Ok I am sure this gets said way to often, but here we go. I was really drunk about two weeks ago and took a couple of hits off a joint that one was really small and two wasn’t that strong. Now I know I can pass a UA and I have some job interviews lined up and totally forgot about hair tests how do you think I would fare with that type of test


        • Jay Z.
          June 26, 2016 @ 7:14 pm

          If you only took a couple of hits off of one joint, and that’s all you’ve done in the past 6 months, then you’ll very likely pass the test.


  3. Berry
    June 20, 2016 @ 5:59 am

    I took a hit or two off a bowl and popped a 60mg vyvanse a month ago. Can’t even remember the last time I did any sort of drug. I have a hair test coming up soon, am I good?


    • Jay Z.
      June 26, 2016 @ 7:09 pm

      yes, I think you’re OK.


  4. Alex
    June 23, 2016 @ 10:00 pm

    If I smoke weed for my third time tonight and have a hair drug test in about 80-90 days will they catch it?


    • Jay Z.
      June 26, 2016 @ 7:01 pm

      IF that’s the only smoking you’ve ever done, then you’ll probably pass.


  5. Jane
    June 23, 2016 @ 11:25 pm

    I was a very heavy smoker for months but I quit at the end of January, do you think I would pass a hair test now? I am a 5’3″ 165lbs woman.


    • Jay Z.
      June 26, 2016 @ 7:01 pm


      If you cut your hair to 1.5″ in length (from the scalp, all around) at any time between now and the test, then there’s an excellent chance you’ll pass the standard hair drug test (90 day history).


  6. Ian
    June 24, 2016 @ 5:25 pm

    I have to take a hair test in a week.

    I do not smoke weed regularly at all. I took a few hits exactly two weeks ago and prior to that I smoked a couple of times from a one hitter over the last 90 days.

    How likely am I to pass?


    • Jay Z.
      June 26, 2016 @ 6:58 pm

      I’d say your chances of passing are good. Good luck!


    • Sara
      August 2, 2016 @ 12:18 am

      Did you pass ?


      • paula spigner
        November 1, 2016 @ 9:17 pm

        Did They? Yes? No?


  7. Jackl
    July 16, 2016 @ 12:15 am

    I smoked .5 grams of marijuana about 8weeks ago (one smoke session) will I pass a hair follicle? Havnt smoked since then or before then?


    • Jay Z.
      July 25, 2016 @ 9:33 pm

      Yes, you are probably good to go (should test clean).


  8. drake brown
    July 18, 2016 @ 6:20 am

    I smoked weed quite a few times a week starting this summer and quit about a week ago. I may be hair tested november or december, what are my chances of passing? please help


    • Jay Z.
      July 25, 2016 @ 9:32 pm

      You have just enough time to clean up your act, if you don’t use again.

      On Oct 31, if you cut your hair down to 3/4″ (all over) or less, then you should test clean from that point forward.

      The main issue I see for you is that you won’t have the minimum length required (1.5″) for a standard hair test, until the end of December.

      Hope this helps,



    • Kelley A Carlson
      October 13, 2016 @ 8:16 pm

      I have been a daily cannabis user for years. Preferred method is vaporizing in case that has any impact on this. I quit on/around September 22 in preparation for a preemployment screening. I tested negative dilute on 2 occasions. The perspective employer has given me 2 options…reapply in 6 months under the same terms and conditions or submit to a hair test which if I fail, I would be completely rejected. This job is an amazing opportunity and I really want to secure it, but financially, waiting 6 months seems like forever. Any insight would be helpful…


      • Jay Z.
        October 21, 2016 @ 8:03 pm

        Kelley, if I were you, I’d abstain and wait the 6 months.

        You’re taking a big risk if you quit on Sept 22 and you take the test any time before the New Year.


  9. T
    July 20, 2016 @ 5:51 am

    I hope you still check this, not sure what your background experience is or how you come to the conclusion of whether or not someone will pass a hair test, none the less, I will ask this question for a close friend of mine.

    End of May my friend smoked about 3/8 grams of weed… maybe over a weekend. June my friend did not smoke any weed. However, during the beginning of July, July 1st, he again smoked approximately 3/8 grams of weed over a day or two.

    Now it is July 19… 18 days since last he last partook in any weed smoking.

    When would it be safe to take a hair test? Would his urine test be clear?

    My friend is 220lbs, 5, 10… has some belly fat, works out every other day, drinks between 32-54 oz of water daily.

    Please advise, I think the Hair test is coming up soon!


    • Jay Z.
      July 25, 2016 @ 9:24 pm

      Your friend is a light user, by anyone’s definition. The hair test is not designed to detect this light amount of drug use. So, he should be fine.

      Re. credentials, etc: I am a friend of someone who had to take the hair test. So, I researched the crap out of this subject (see research on home page); later, I built this website to share what I learned with everyone else.

      The math to determine if you will likely pass or not is actually very straightforward – read our home page, especially comments, to learn more about it.


  10. Anthony
    July 20, 2016 @ 11:12 pm

    I smoked 3 times last week and I have a hair drug test next week. Before that I haven’t smoked in almost a year how likely am I to pass the test?


    • Jay Z.
      July 25, 2016 @ 9:17 pm

      Chances are good you will pass. Best of luck!


  11. Rob
    August 14, 2016 @ 1:58 am

    I have a upcoming drug test, I haven’t smoked weed in 4 years. Is there anyway I can test positive for weed? I also have very long hair. Wondering how much hair they will test.


    • Jay Z.
      August 15, 2016 @ 10:39 pm

      No, you won’t test positive if it’s been 4 years. Even with long hair. Make sure they take clip the 1.5″ sample from the scalp outwards (as they are supposed to), and you’ll be fine.


  12. hewitt
    August 16, 2016 @ 12:42 am

    if u smoked twice a month for 6mos, stopped in June, now have to take hair follicle test in aug, will you pass?


    • Jay Z.
      August 18, 2016 @ 10:34 pm

      No, you will probably fail the test.


  13. Granny
    August 25, 2016 @ 7:24 pm

    I am 62 years young, I chose to read an article on THC detected in hair. Very interesting!


  14. Kinda Worried
    September 2, 2016 @ 5:01 am

    I’m surprised at all the comments asking about personal usage and possibility of passing, but even more shocked that you respond to all of them. I’m sure everyone appreciates that.

    Well here’s my dilemma. I stopped smoking for 2 years, so I had absolutely no THC in my system whatsoever. Just recently, over the past week I have smoked 2.5 grams of bud. I’m not even sure that I will have to take a hair test, it may be a urine test.

    Do you think the THC will show in the hair test? If so, I’m assuming I’ll need 90 days to be clean. What are your opinions on probability or even if it will be detected? I greatly appreciate any response. Thank you.


    • Jay Z.
      September 8, 2016 @ 10:10 pm

      I would not be that worried. The hair test isn’t designed to detect one-time use, especially of that small amount.


  15. Rob
    October 29, 2016 @ 5:11 pm

    This my first time being tested using a hair test. Last time I smoked would have been at the beginning of august. I’m not a heavy smoker. Just a social one. They pulled from my under arm hair today which has never been cut. Do you think the test will be positive


    • Jay Z.
      November 12, 2016 @ 4:34 pm

      Yes, you are at risk if they sampled underarm hair.

      Body hair grows much slower than head hair, so it records a far longer period of use, per inch.


  16. Blake
    November 1, 2016 @ 3:15 pm

    I had 2 hits from a pipe over a month ago. This is the only time that I have smoked. What are the chances it shows up on a hair test?


    • Jay Z.
      November 12, 2016 @ 4:32 pm

      Very low risk you will fail the test.


  17. Smither
    November 7, 2016 @ 1:36 am

    Hello there,

    I have smoked on and off (probably a few times a month) over the last couple years. I have long hair, and don’t want to cut it away if I can help it. Do you reckon I could pass a hair follicle test taken mid-late next year? Would it be clean by then?



    • Jay Z.
      November 12, 2016 @ 4:22 pm

      If don’t use any more until then, you should be OK.

      The test station will cut your hair at the scalp line, then cut it again and throw away hair that’s older than the cutoff period (usually 1.5″ for 90 days).

      The risk with keeping longer hair is human error. Sometimes, a sample station tech won’t cut the right length. At the lab, if they can’t tell which end is which, they may be forced to test the whole sample. So, what should have been a 90-day test ends up being a 120-day test.

      That’s why I always recommend cutting hair down to 1.5″ right before the test, just to be sure. But I understand not everyone can do this.

      Best of luck, Smither!


  18. Tim
    November 8, 2016 @ 8:08 pm

    I have amoked for years…I recently quit 6 weeks ago to look for a better job..I have a test comming up in about 2 weeks…Also I have long hair…is it possible to pass a follicle I need to cut my hair? Do I need to wait longer?


  19. Spot
    November 11, 2016 @ 11:36 pm

    I haven’t smoked ib 8mos qn 30 days ago i took a hit of some good weed i hqve a new job opportunity and they hair test will i fail or pass..if i need to wait how long should i wait in what should I do to clean up….if i wait smoked 100days will my hair follicle be clean…… Please help truthful answers only


    • Jay Z.
      November 12, 2016 @ 4:03 pm

      I think you are fine. I wouldn’t worry if you only used once in 8 mos.

      Good luck!


  20. Louise
    November 29, 2016 @ 10:21 pm

    I had to take a hair follicle test today for court to get a base-line level of thc. I am a heavy smoker, and I have smoked just about everyday for the last 3-1/2 years. The judge said that that the levels better be lower in 90 days. My lawyer thinks if I just cut it way down, I can still occasionally smoke and still get my levels to go down. Does that sound right, or would i test completely clean in 90 days if I stopped now?


    • Jay Z.
      November 29, 2016 @ 10:43 pm

      I assume that when the judge says, “better be lower”, it means: “you better pass the test”…?

      If so, then your lawyer is giving you bad advice.

      You should stop cold turkey, right now, to have a chance of passing the test in another 90 days.

      You still may not pass, because a heavy smoker needs at least 110-120 days of abstinence to yield a 1.5” clean hair sample.

      Perhaps that’s what the judge meant (he probably knows how the tests work).

      All the best,



  21. Jay
    December 8, 2016 @ 5:11 pm

    Hello, I smoked regularly for about a year until a great job offer came my way. I stopped smoking around the end of June and have been clean since then. How likely do you think it would be for me to pass a hair follicle test if it is around the end of January 2017? would really appreciate a reply Thank you!


    • Jay Z.
      December 15, 2016 @ 11:14 pm

      Your chances are very good.


  22. Luis
    December 12, 2016 @ 6:16 pm

    Hi I haven’t smoked in years but in mid october I took 2 or 3 puffs of weed (joint) and i will have a hair follicle test in end of December or beginning of January what are my chances of passing the test??


    • Jay Z.
      December 15, 2016 @ 11:02 pm

      Your chances of passing are excellent. That is a very small amount.


  23. Jay
    January 13, 2017 @ 6:45 am

    I regularly smoked for the last 2-1/2 years. My normal hair length is 1/2 inch, and I am not sure where they are going to pull the hair from. I am a 39 year old male, body builder, excellent nutrition, and 15% body fat. I have a couple of questions. I am going clean tomorrow in anticipation of an upcoming hair test for employment. I would like to take the test in 2 months if I can pass it.

    1. If they take arm pit hair as my head hair is too short, would shaving it a month prior to the test be effective?

    2. With my high metabolism, daily exercise, and healthy diet, is it possible to have it out of my system to pass a hair test sooner than 90 days?

    3. Are there any detox remedies that I can start using now, that will help the process of removing THC from the hair follicle? A detox shampoo treatment the day / week before the test will not work in this situation. They test randomly while on the road and there is no way to run for a quick shampoo.

    Thanks so much for your help. This job is a life changer, and will really help my family.


    • Jay Z.
      January 14, 2017 @ 4:55 pm


      Since your scalp hair will be 1/2 inch at the time of the test, then there is a good chance they will sample your upper body hair, if they can find enough.

      1. re. arm pit hair: shaving a month before is a good strategy to rid your armpits of traces; however, it also doesn’t leave enough hair to sample

      2. no, your metabolism won’t make much of a difference; your metabolism has very little impact on how fast your bloodstream eliminates/breaks down TCH-COOH stored in your body fat. The fact that you have low body fat helps to some degree, but not nearly as much as people think. After all, 15% body fat in a 200 lb man = 30 lbs of fat containing drug traces.

      3. the only way to rid your hair follicles of TCH-COOH are (1) be clean for ~100 days + cut the bad hair away; or, (2) try to clean your hair using the two methods mentioned above. I’ve seen no credible evidence that edibles, pills, drinks, etc. make much of a difference on a hair test.

      Best of luck on your test!



  24. Zach
    February 20, 2017 @ 4:54 am

    Smoked less than .5 grams total on January 1st and 2nd in Denver. Might have a hair follicle test in mid-March or late March. My hair is about 1.5″ right now. Will I pass the test? I don’t use regularly, 1 other time in early December, then nothing before that.


    • Jay Z.
      February 21, 2017 @ 5:00 pm

      You’ll probably pass, is my guess. But kinda cutting it close.


  25. Sam
    February 28, 2017 @ 8:26 pm

    I’ve been 500 days clean will I pass? Did a bit of mandy before that too



    • Jay Z.
      March 1, 2017 @ 4:53 pm

      I can’t see how you could fail, after abstaining this long.


  26. Douglas P.
    March 8, 2017 @ 10:22 pm

    The last time i smoked was in October of 2016. Took a hair sample from my armpit the 1st of March 2017. FAILED! The lab that did the test was Quest Diagnostic.


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