Your quick guide to the urine drug testing for cannabis use and what strategies work to beat the tests.

In most cases, urine drug testing for cannabis is an invasion of privacy and a giant waste of resources. However, until drug war hysteria is a thing of the past, it is a reality that we will need to deal with.

Unfortunately, the amount of misinformation on the internet about drug testing is astounding. My unscientific estimate is that 85% of what you read about drug tests and how to beat them is utter bullshitMany people writing about drug testing are, at best, well-intentioned but with no clue, and at worst, purposely misleading you for commercial gain.

This article will provide you with

  • A basic understanding of urine drug testing for cannabis
  • Strategies to beat drug tests that work and those that are just myths

[Always test yourself to know whether you’ll pass! Here are the test strips I recommend.]

 

Urine Drug Testing for Cannabis Use

Let’s start with an infographic to give a quick overview:

Infographic-urine-drug-testing-marijuana

Specimen Validity Testing

After collection of the urine sample, the first thing a lab will do is check whether it is a valid urine specimen. They want to make sure you didn’t substitute the urine for something else or add anything to it. They may check the following:

  • Color and appearance: Urine should have normal color and not be cloudy.
  • Temperature: Urine should be within normal body temperature range.
  • Creatinine: This is a by-product of protein metabolism. Low levels of creatinine may indicate that specimen is not real urine or that it has been diluted.
  • Specific gravity: This tests the density of urine. Similar to creatinine, it ensures that specimen has not been overly diluted.
  • pH: Urine should be within normal pH range, as extremes of pH will interfere with the drug tests.
  • Adulterants: Adulterants are any substance added to the urine to cause a false negative on the drug test. Many oxidizing agents (e.g. bleach) will do this. Common adulterants are now tested for by many labs, although what specifically they test for may vary.

Types of Tests for Cannabis Use

Urine drug tests for cannabis use do not test for THC itself since little THC is actually excreted into the urine. Rather, they test for metabolites of THC, which stay at detectable levels for much longer (It may help to be familiar with the basics of THC metabolism).

There are two types of tests that can assess cannabis use:

  • Immunoassay test
  • GC-MS test

The immunoassay test is used as a rapid and cheap screening test. This is the same type of test that is used in point-of-care home drug testing kits.

So why don’t drug testing companies just use the immunoassay test by itself? The problem is that it produces a high rate of false positives  – it gives a positive result for cannabis use even when you have not ingested any cannabis.

The drug testing companies are obligated to use GC-MS as a confirmatory test to ensure you have actually used cannabis. The confirmatory GC-MS test is extremely specific – it produces almost no false positives.

So why don’t drug testing companies just use the GC-MS test? It uses expensive equipment and is much more time consuming. Companies would either need to charge more for drug testing or accept a much lower profit margin.

One proposal has been to spike all urine samples with something that will cause a false positive on the immunoassay (while still passing the GC-MS). Drug testing companies would be forced to spend a lot more money on confirmatory tests. Eventually they would have to raise prices, reducing adoption of unnecessary drug testing!

[Always test yourself to know whether you’ll pass! Here are the test strips I recommend.]

 

Beating Cannabis Drug Tests

What actually works for beating drug tests and what doesn’t? Much of the information out there is wrong. Drug testing myths get endlessly repeated.

I will cover every strategy for beating cannabis drug tests and evaluate whether there is any evidence that it actually works. Each article will have an in-depth scientific explanation, so you know that it is for real.

Come back regularly, sign up for the mailing list, or follow me on Twitter/Facebook to see when there is a new update!

Strategies That Don’t Work

Strategies That Do Work

[Always test yourself to know whether you’ll pass! Here are the test strips I recommend.]

Last modified: September 11, 2017

40 Responses to " Guide to Urine Drug Testing for Cannabis "

  1. Fred says:

    Thank you for your info. In short, I have been a heavy user of high quality flower. I have had urine tested in the past and was clear at 30 days, albeit lower quality of bud.

    My last test (as mentioned above) my body weight was 190 lbs. I current weigh 150 lbs….Yes I have lost body fat..lol.

    Currently I have a scheduled pre employment urine due in 16 days.

    I’m 31 days abstinent and show positive with home test. To say the least I’m a tad worried….

    Note: the home testing has been with little hyperhydration and no morning voids…

    Any advise would be greatly appreciated.

    P.S. I do have one option of push test forward by 7 days but would like that as last resort…oh, thought I had great DNA, maybe not for this instance.

    • 16 days is still a lot of time. It would be very rare to test positive after 47 days of abstinence, especially at lower body fat (good job on the weight loss by the way!) There can be a lot of variability in test results, with urine concentrations varying up to 3-fold even within the same day.

      Drinking enough fluids immediately prior to the test can make a big difference. I would continue using the home test strips every few days, but with drinking extra fluids in the hour before you test yourself.

      You can also use activated charcoal, which will help clear your system faster. There is solid evidence that this works, and I am writing up an article on it now that will have further details. Good luck!

      • Fred says:

        Thanks Prof,

        Ah, activated charcoal, brings me back to working in the ER days..

        Would zinc also be a worthy try?

        In addition, I have been consuming alkaline antioxidant H2O….not specifically for this issue but feel it may also assist with the “clean up”.. What is your opinion ?

        You have a great page and I plan to follow regardless of my current status.

        Thanks again for your valuable time and consideration.

        • Thanks for your support!

          Some people doubt activated charcoal works since they think that THC metabolites don’t go to the GI. However, due enterohepatic recirculation, the THC-COOH metabolite is constantly cycled in and out of the GI tract where it can be trapped by activated charcoal. This has already been proven by a pharmacokinetic study. I will provide more details on this soon.

          I haven’t researched zinc in depth yet, but from a quick search, it looks like it is worth trying. Taking the right dose is probably the key.

          Antioxidants shouldn’t make much difference since they won’t directly affect either THC metabolism or redistribution of THC & metabolites from fat.

          The alkalinization probably won’t matter much either. Almost no THC-COOH is directly excreted into the urine, which means that it is almost completely reabsorbed in the renal tubules. In theory, alkalinizing the urine could cause an ion trapping effect that would block this reabsorption and lead to more excreted in the urine. However, given the pKa of THC-COOH, it is probably not possible to achieve such low urine pH that significant ion trapping is achieved. Besides, there may also be active transport that would negate the effect of urinary alkalinization. Basically, it is theoretical and probably doesn’t do anything.

          There is one other strategy – to inhibit the enzymes responsible for glucuronidation of the THC-COOH metabolite. I am also working on a write-up for this, so stay tuned.

          • Fred says:

            Will do!

            I’m considering charcoal 1 week prior to test date.

            Will keep you posted if ok…

            Cheers

  2. quinten says:

    i have a drug test in 8 days and ive only smoked 2 times last week and 1 time the week before and about 2 times the week before that week and i think once again the week before THAT week also.. alot of week i know… what can i do now since ive stop smoking since saturday to flush out of mask the thc that may still be in my body, on sunday i was doing cardio for 40 min sweating alot and went into the sauna for 20 minutes,, (im not an everyday user, i smoke sometimes or less) and then on monday went for another run in my neighborhood, and since sunday ive been drinking 8 small cups of water a day? will i be ok by the time june 8th rolls in?

  3. quinten says:

    i am 163 pounds also

  4. Fred says:

    P.S. I passed at 49 days, however, went heavy on hydration pre-test and came out diluted…Ooops…was self testing prior with home strips showing faint line negative… The. First results scared me being a straight out “lab” test with SVT applied!!

    All good and happy to be in spot I am..

    Thanks again Doc…. I did do a few rounds of charcoal…

  5. Heisenberg says:

    Thank you profofpot!

    i’m worried i will fail my drug test. i smoked 4 times last month and i have a drug test that is needed within june 12-16 for my internship and since then i’m gaining some pounds. will i pass it?

    p.s. my last session was in may 25.

  6. Glen James says:

    Amazing site providing truly quality resources…. thank you!! I’ll keep this short and sweet – male, 31, 5’9″, 165lbs, sz 32 waist, probably 15%ish body fat. I smoke 3/4 times a week. Taking pre-employment drug test on what will be my 10th day clean. Odds of passing? Suggestions to help??

    Eternally grateful for your time and the information you’re providing. On my way to the store to get a bottle of activated charcoal right now.

  7. Glen James says:

    Following up from my previous comment – just passed at On Home test on Day 6. Feeling a million times better now 🙂

  8. Jusswavy says:

    I weigh 105 barely workout an it’s been 40 plus days of being sober an still tested positive!! Any advice doc? Btw my metabolites were low so what he hell gives!!

    • Prof of Pot says:

      40 days is a really long time, but this has been seen before in heavy users. What type of test did you take? I’m a little confused, because if your THC metabolites are low, then you should pass. Can you explain further?

      • Jusswavy says:

        It was a urine analysis test but I also was drinking a lot of water days before so could it possible that they decided to fail it because of the amount of water I drinked that made it look like I was trying cover it up!??

  9. Jusswavy says:

    The only details they gave me was that my metabolites were low, it’s crazy because I used to be a moderate smoker of weed an the fact I weigh less than 110 with 40 plus days of being sober it’s like I’m all out of theories of what could it be because I know it ain’t the cigarettes or other tobacco related products. Since then I’ve been taking detox products like 3 days cleanse an anything cranberry related products, sweated a lot, drinked water and a occasional soda .. I virtually have little body fat on me I’m lean with some muscle 🤷🏾‍♂️.. am I being sabotaged I’m all out of theories and money 🤦🏾‍♂️ it’s very odd how folks who weigh more than I do pass these drug tests so easily I’m skinny for Christ sake 😂

  10. JohnnyD says:

    Recently urine tested for employment after staying entirely clean of weed for 30 days. The test was one of the color-change types, similar to a pool or spa water test strip.To my surprise, the result came up positive not for weed, but for adulterants of some sort. They put it as “No clear result for marijuana”. Trouble is, I never used any adulterants, ever. Any idea how this could happen? They sent the sample off to a lab for further testing, which I hope will give a better result, but the ambiguity may have already cost me the job.

  11. JohnnyD says:

    So let me get this straight – if I don’t become a subscriber, you don’t publish my comments? Is that how this works? Because if it is, you can fuck off and earn your money off of someone else.

  12. Mike says:

    I go to a day report center and get drug tested frequently. My last drug test for THC got me a two week shocker in jail. I have not smoked and am a male 6’4″ 410 lbs and have not smoked pot none whatsoever. I missed the 4th of July with my family and crushed me. I should have been cooking out and letting fireworks off with my son. I urinated once and didn’t meet the mark so I had to use the same cup again and I believe that is what caused the spike due to clean catch protocol not being followed. I don’t know the specifics but what do you all think? Thanks for any replies.

    • Prof of Pot says:

      Hi Mike, I’m really sorry that happened to you on your 4th of July. Such a shame that our justice system thinks it is more important for you to be in jail than to be with your family. It is impossible to say for sure why you didn’t pass the test. I looked at the clean catch protocol (profofpot.com/midstream-urine-drug-testing-cannabis/) and there is not any evidence that this is a factor. It does sound like you were dehydrated though, which can concentrate THC metabolites. Next time, I would drink plenty of fluids in the hour before the test to dilute your urine.

  13. Lou says:

    How long does THC stay in sir of a not so well ventilated room? Roomy is a pothead and I am afraid I will fail my test because of exposure. I’m 5’5 165 lbs ~25% body fat and female. I’ve abstained 72 days but still coming up positive on home tests. Do you think it’s cause of the roommate?

    • Prof of Pot says:

      I would be pretty surprised if you failed due to second hand smoke (unless we’re talking hotbox level of second hand smoke). But also 72 days should be more than enough time to clear your system. You could try avoiding the smoke for 5 days and retesting yourself. If this doesn’t produce a positive, then I suspect that the home test is giving you a false positive.

      • Lou says:

        Thanks!! I did 2 days of the activated charcoal to be safe at 5g/day and FINALLY I’m getting a negative home test. I’ve got a test at end of week. You suggest 2 days on charcoal and 5 days off. Do I have to wait or can I squeeze in another day of charcoal? (Yes I’m over panicked, must pass…) Thanks for the advice!

        • Prof of Pot says:

          2 days on and 5 days off is just a suggestion…it is not set in stone. You can always take more, but the longer you take it, the more you risk some uncomfortable side effects such as constipation. I think if you are that desperate to pass, it could be worth it.

  14. Jusswavy says:

    My drug test came back positive as the same metabolite level before which is 47 so I’m starting to put two an two together am I being sabotaged? Because they is no real reason why my metabolite level will stay the same after 70 plus days of not smoking weed! I really feel like they sabotaging my employment!

  15. A. says:

    Hello Prof-

    I was a heavy user but stopped completely and tested preliminary positive on 3 different home tests over days 33 and 34 of abstinence. I weigh 195 lbs, exercise 4 days a week and drink several quarts of water a day. I would guess my BMI is around 15-18 (I’m stocky but not fat). One week until my pre-job urine test.

    Do you have preferred brand of activated charcoal?
    Could my ketogenic/high-fat diet be a problem?
    Are there any strategies you would suggest?

    I’m freaking out and any help would greatly be appreciated. Thanks.

    • Prof of Pot says:

      I’ve been meaning for months to recommend a brand of activated charcoal, but unfortunately I haven’t had time to research it. People seem to like the powder ones instead of the capsule ones because they can take larger doses. I don’t think your diet will necessarily be a problem, except that if it doesn’t contain any fiber, you may have missed some opportunity. Fiber somewhat acts like activated charcoal, although it is weaker. At this point, just go straight to the activated charcoal. I would continue to exercise, cutting as much fat as possible in the next week. On the day of the test, drink plenty of fluids to dilute the urine.

  16. Nick says:

    I there I smoked today but I have a test Monday they said that my levels need to be lower than the last test it was last Thursday it’s a po test would activated charcoal help if I did it for the next 3 days cuz I really want my levels to go down I plan on not smoke anymore till I get off please Lmk if I should get some to help me out

  17. Nick says:

    Prof please help I’m going nuts and I’m a heavy user what should I do to lower my the levels prof and comments would be great

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