How to avoid a false positive, DUI for Cannabis


How to get rid of THC residuals from earlier consumption and avoid a false positive.


How to avoid testing positive if you consume weed responsibly, and yes, you can get busted if you're not stoned.

False-Positive Results in 5% to 10% of Cases - Dwight Smith, MD  



The good Judge made these observations when he found Mr. Carrall not guilty of drug-drivingMr. Carrall had been pulled over by a police and tested positive for THC, nine days after smoking a joint.Lismore magistrate David Heilpern described the current testing for cannabis as a 'mystery and uncertain-by-design.'  


Point by Point Issues - On the Spot Weed Testing.



  • employees are fired for smoking on their day off.

  • DUI for cannabis is given when THC residues are in the saliva, even if you're not really stoned.

  • marijuana consumers need to be ways to fight unfair, unreliable testing.

  • cheap saliva tests are administered on the spot.

  • the saliva test weakness, give a lot of  false positives, which allows for a good lawyer to challenge the test.

  • saliva test picks up weed consumption only 12-24 hours before consumption.

  • limit of detection depends on the person or duration of exposure.

  • how to make the response lower and detection time shorter? take water, brush teeth, gargle low concentration hydrogen peroxide, mouthwash,

  • myths, things that don't' work, sucking on a pen, oral detox help - are no better than hydrogen peroxide and cost 10 times more.

  • sucking on anything, like mints, that produces saliva, helps clear out residual THC from hours ago, which may lead to a false DUI


"Prior to driving or going to work, you want to brush your teeth. Rake the plaque off your tongue. Gargle with 1% H2O2  (hydrogen peroxide) 99% water.  Then take a cotton ball and clean your entire mouth. Immediately before testing, take a mouth full of the H2O2 solution and gargle and swallow.  What this does is get the old saliva from hours ago out of your mouth, and also residuals that are stuck on your tongue. The peroxide cleans the mouth thoroughly of residuals."  - Resident Medical Opinion


To get a better picture of the tests' flaws, Smith and colleagues at Boston Medical Center reviewed scientific articles on drug screening published between January 1980 and September 2009.  In a saliva drug test, a tester uses a swab is placed between the lower cheek and gums for a few minutes.  The swab is placed in a small cup, where the saliva and its components react. THC and other drugs show up like a miracle (or nightmare) in color.


on the spot weed test

The problem is that manufacturers and users (lawmakers, employers) claim that the accuracy is much greater than is the reality.  Check this out.


"I mean, the tests are pretty amazing science, but too many of them are dodgy and are in fact, in some cases, they are designed deliberately to give false positives.  Incredibly sick.  You can debate why all you want, but this can be the case." - Johnny Rodriguez - Conspiracy Theory


American Psychiatric Association presented some interesting results on common spot drug testing methods in saliva, urine, hair and blood.  The overall results are astounding, where false positives were estimated to range from 5 to 10%.   Certainly, there are large variations depending on the method and parameter (type of drug) tested.  However, the most common test methods were the ones with greatest amount of error.  


"You want to get residuals out of your pie-hole that might cause a false positive." - Johnny Rodriguez


Onsite drug tests are seldom, if ever listed with an accuracy of 99%.  Scientific American suggests that the average is 5% false positives among common saliva and urine for drugs like THC, the main ingredient of cannabis.  Even if a drug test is 99% accurate, that means that one in one hundred innocent people are put through the ringer.  Depending on the law enforcement agency and jurisdiction, a false positive could stick because they don't share in the American Psychiatric Association's findings.


Further, given the vastly overly conservative number of 1/100 false positives, this means that in the course of a couple of years, if a person was subject to 10 tests, then the chance of a false positive is 10% or 1 in 10.  If the test is 95% reliable, with 5% false positives, then the probability in 10 testing events is an unacceptable 1/2.  Now your blood is drawn, and sensitive testing might pick up the intake of one good joint smoked one month ago.  Depending on the interpretation of the results by the local Judge, who may not really understand what' going on, a person that's innocent can be fined, jailed and / or fired, over a joint.


While the lawmen play around with roadside testing schemes for marijuana, innocent people that smoke marijuana on occasion and not to excess don't need the hassle of a false positive.


And the police and judiciary don't want to play around with non-crimes either.  


An employer may administer a saliva drug test on a job site any time. Therefore, it is wise for responsible users to be prepared for a random test.  Employers and police prefer using the saliva drug test because they can “catch” people by surprise on the spot.  It is advisable for those wish to medicate with cannabis to insure saliva is “clean”, by getting their own screening kit test. Kits can cost only $20 and most reviews and reports are surprisingly good, nonetheless, watch out for scammers.


"If you're high as a kite and get a DUI, too freakin bad.  But if you get busted for smoking a single joint three hours earlier due to testing positive for residues in the mouth, that is a travesty of justice.  Most cops don't want this, the Judge probably doesn't want this and you definitely don't want this. Take care of yourself and learn what to do." - Johnny Rodriguez


Clearly, the advice is not to drive while impaired, whether it be with alcohol, lack of sleep, medication, pot, and narcotics.  Clearly, THC in excess impairs many people's ability to operate complex machinery, and drive.  The idea of using a technique to avoid a false positive in a saliva test is to reduce the risk of a false positive, where minimal consumption levels of THC and substances that cause false positives are reduced in testing.  


The methods used to reduce THC in a saliva test won't necessarily protect a person that is really stoned.  The good thing about cannabis, is that when people get really high, they don't want to drive.  People with adverse reactions from over consumption include anxiety and paranoia, and in this state of mind, the last thing they want to do is reach for the car keys. Further, cannabis tends to make people more careful and drive slower.  


However, marijuana on average impairs spatial perception, in some but not all people.  A study of 50,000 accidents revealed that marijuana users and sober drivers had the same accident rate, whereas alcohol abuse and driving was an obvious problem. Since marijuana over all seems to provide positive and negative effects to driving, that balance out, and make it equivalent to driving stone cold sober.


With that said, there are the outliers, people who are outside of the normal curve and drive while they are high as a kite and drive.  This article is not about protecting them.  In fact, the methods to avoid testing positive might not protect them from a positive.  The methods here have a high probability of protecting someone who consumed a moderate amount of marijuana several hours before driving, who are not impaired to any extent, or might test positive due to something they ingested, which fouled up the test.


"Cold medications, the antidepressant Wellbutrin, and tricyclic antidepressants can trigger false-positive results on tests for amphetamines, according to the review, and the antidepressant Zoloft and the painkiller Daypro can show up as a benzodiazepine problem. The quinolone antibiotic drugs can trigger false positives for opioids, and the HIV medication Sustiva can show up as marijuana use."


Contrary to urban myth, second hand smoke is not going to show up on roadside tests.

Drug tests generally produce false-positive results in 5% to 10% of cases and false negatives in 10% to 15% of cases, new research shows. Eating as little as a teaspoon of poppy seeds -- less than the amount on a poppy seed bagel -- can produce false-positive results on tests for opioid abuse." - Dwight Smith, MD, of the VA Medical Center in Black Hills, S.D.

The poppy seeds can lead to false-positive results for two or three days, he says, yet one recent study showed only about 50% of doctors were aware of the problem. Knowing the tests' limitations is crucial given that about 150 million drug tests were conducted in the United States last year, he says


Compared to a blood, urine test and a hair test, the saliva test is the easiest to pass. It is imperative to be prepared for a test at all times. Saliva tests are used because they can catch employees at any time, on the spot. Mouthwash alone is a help but in itself is risky.  Products that work? Consider Toxin Rid Rescue Wash (looks good, you do your research).


42OEOL - The saliva test has little to do with the GCMS test.  The saliva test is based on a chemical reaction with THC, but a number of other chemicals give false positives.  However, the GCMS test is much more precise, only THC like compounds are extracted, then the sample is heated, and only compounds with a specific boiling point are analyzed, and finally, the compound is ionized, where it shatters into distinct pieces, (mass charge units) that are detected. A computer matches up the fragments with a library of compounds and gives a % probability of a positive.  Basically and functionally, positives of an A and B sample using GCMS means you're busted, 99 times out of 100 or better.



Advice: After you read this round table discussion, which contains everything, jokes, bro-science, and usable testimonials.  Go back and read the above material and collect your takeaway.  


Obviously the way to avoid testing positive is to not take massive amounts of a drug.  We're in no way condoning drug abuse.  The theme is about a medical patient, that uses a non-impairing quantity of cannabis medicine to treat their conditions and symptoms, and want's to avoid a false positive on a DUI or employer test.





I'm going to have to take an oral swab drug test tomorrow, more than 24 hours from now. I last smoked ~12 hours ago, and I'm not going to smoke till after my test. Will I be in the clear? What can I do to further ensure that I will pass?  I an idea, drop your pants, locate your balls and ask i want to work for a company that thinks it's ok to steal my body fluids and do a rectal mind probe into what i do in my free time? Workplace safety my ass. Wake up fool!

I'm inclined to agree, but I really need this job.


"Prior to driving or going to work, you want to brush your teeth. Rake the plaque off your tongue. Gargle with 1% H2O2  (hydrogen peroxide) 99% water.  Then take a cotton ball and clean your entire mouth. Immediately before testing, take a mouth full of the H2O2 solution and gargle and swallow (its used in dental offices).  What this does is get the old saliva from hours ago out of your mouth, and also residuals that are stuck on your tongue. The peroxide cleans the mouth thoroughly of residuals."  - Resident Medical Opinion


yesyesyesI've taken an oral drug test before and passed. I had read somewhere that the retsin in certs miniminter would help, not believing this I: 1) gargled with scope 4 or 5 times before the test 2) gargled with hydrogen peroxide 3) ate about a box of mints on the way there 4) had taken a clean out kit thinking that if i failed i'd volunteer for a piss test then and there. 5) put 2 mints under my tongue before they put the swab in my mouth. It was a fearful couple of minutes but I passed. I don't know what the combination worked....

yesThanks, this is the most helpful advice I've received so far. How long had you abstained from smoking before your test?




I smoked a quarter the night before with a couple of friends.

It's been a day now, how did things turn out?

I just got back from my first day on the job. I had to stick this nasty ass tasting swab in between my cheek and lower jaw for 3 minutes, but for the most part i held it at an angle (it was like this flat, rigid thing on the end), so it wasn't getting very much saliva from me. They have to mail it off, so it will be a while before I find out the results. I don't think I'm gonna smoke till I have the results, that way just in case it does come back failed (which at this point I doubt it will but I'm playing it safe) I can say "Whoa, that can't be right, I don't do drugs! You can even give me another one to prove it!"

yesIf you don't smoke every day, you should be ok. Usually the saliva test can only detect as far back as about 14 hours. Saliva tests mostly catch people who are so addicted they do drugs every day. All of this info is on wiki.

Your not addicted to weed because you smoke everyday.

I do smoke every day.

I've been brushing the sides of my mouth along with using listerine 3x daily. I'm hoping this will be enough

yesAs far as drug tests go, the saliva-based ones are the best for us stoners, it puts the rate of detection on par with other drugs. You should be good, when in doubt always try to clean the system out with water, lots and lots of water.

yesNot really it detects weed when you aren't actually stoned, so i wouldn't consider this on par with a breathalyzer.

I hadn't considered the breathalyzer, with this being the marijuana reddit and the breathalyzer being almost exclusively for alcohol. I would prefer a saliva test to a urine, blood, or hair analysis, which can keep information on what you've done for a lot longer than saliva.

I was actually kinda hoping for a piss test, cuz I have an unused bottle of synthetic urine... now I have to go in worrying whether I will pass or not.

Go to your local head shop, they will usually have something, i used a mouthwash one time that got me my old job, it was just a mouthwash that had something or other in it. worked for around to the head shops, good luck man.

yesWhen I was reading up on Salvia before trying it, I came across some helpful information in some research papers. Salvia has a half-life of 56 minutes. You'll be just fine.

Listerine won't help you. I'm sorry to say your pretty much fucked.... next time quit sooner and drink lots of water to help purge your system. Post again and let us know (truthfully!) how things worked out for you.

yesyesGood afternoon. I'm just wondering about experiences with this test. I smoke joints pretty often, about 1 to 2 a day. Yesterday I smoked about half a small joint in the morning, and then I smoked one hit from a freshly rolled joint at about 10-11 PM that night. This morning I woke up fully prepared to sub for a piss test with Quick Fix. I went up to the place where I was offered a job to fill out and sign paperwork like W2 etc and take the test. Well after I finished filling out all the paperwork it was sprung on me I had to take an Oral-Eze swab test that's sent to Quest lab. I basically knew right there I failed, but I've been reading everything I can about user experiences and I've read some have passed even after 8 hours of not smoking. I should hear back in 2 days my results. I brushed my teeth after taking that puff last night and then again this morning with my electric toothbrush. Drank some water on the way to the place. Should I go ahead and look for another job?

yesAbout Your Test. If your last dose was >8 hrs before your test, I give you a 50-50 shot of passing, depending on the lab's procedures & equipment. If you're lucky, they just do a basic swab and no advanced testing. You will most likely pass unless you had a dose ~10 hrs before the test...if you did, you're pushing it If they use GC/MS or any kind of advanced spectrometry, you will very, very likely fail...that being said, medical-grade lab thresholds are 5μg/L; a lot of drug-testing labs I've seen have thresholds of up to or more than 5x that. If that's the case for Quest, you may have a good chance of passing. Some labs will do a basic test and if you turn up positive for that, they will investigate further with a GC/MS method and reveal more. Just hope you pass the first round.


420 EOL - The saliva test has little to do with the GCMS test.  The saliva test is based on a chemical reaction with THC but a number of other chemicals give false positives.  However, the GCMS test is much more precise, only THC like compounds are extracted, then the sample is heated, and only compounds with a specific boiling point are analyzed, and finally, the compound is ionized, where it shatters into distinct pieces, (mass charge units) that are detected. A computer matches up the fragments with a library of compounds and gives a % probability of a positive.  Basically and functionally, positives of an A and B sample using GCMS means you're busted, 99 times out of 100 or better.

I had quite a few scholarly articles sourced here, but there's no way I have time/patience to go back and link them now...basically it boils down to this:

Type of test administered & the parameters of that test (method, sensitivity). Again, hope they use a cheap/quick method that doesn't have a low threshold because those lingering cannabinoid metabolites will come back to bite you in the rear

Type and concentration of various cannabinoids (i.e., THC-COOH has a much, much longer elimination time than most other cannabinoids) in your system

Time since last consumption--measured in hours, not days. According to my research, concentrations were undetectable in average smokers as little as 2.5hrs later with a median of 6 hrs


thc reaction in saliva test

yesThere's wildly conflicting data on the correlation of plasma concentration & cannabinoid retention with detection in OF (oral fluid). Essentially you can have a very high plasma concentration of THC and it won't show up in your saliva test. This is attributed (mostly) to the contamination of your mucous membranes when you smoke cannabis

yesyesI don't like "calling people out", but he has some pretty terrible info and even worse advice. No offense Tom_Bom, 1. There's no definitive time of "7 days" (or whatever) that determines how long it takes cannabis and its metabolites to be eliminated from your system. It varies wildly and doesn't apply to a saliva test--see the plasma concentration paradox above and feel free to Google it since I lost my beautifully-typed sourced response  2. Please DO NOT tell a drug screening company that you use recreational drugs. IF you get that call, the only card you have to play at that point is to ask for a second test. They will probably say no, but that's better than telling an organization whose sole purpose is to eliminate drug users that you use drugs. As a professional, you should keep that to yourself anyway. As a medical professional, the whole "my doctor prescribed me alternative medicine in the form of marijuana" will not get you very far. If you were in a state that allowed medical/legal marijuana, you wouldn't be worried about this to begin with. Don't follow this guy's/gal's advice for your own benefit.

yesyesyesOur oral fluid drug testing panels detect commonly abused drugs and yield reliable results that are defensible in court, meaning you can screen with confidence. Methodology A two-tiered testing process ensures that positive results are re-checked and confirmed. The initial oral fluid specimen is screened using enzyme immunoassay (EIA), a proven reliable methodology for routine drug testing. Confirmation Any samples that are presumptively positive in the initial tests are confirmed, utilizing another portion of the oral fluid sample, using either gas chromatography/mass spectrometry (GC/MS) or gas chromatography/mass spectrometry/mass spectrometry (GC/MS/MS) technology. Certifications Quest Diagnostics Employer Solutions testing locations hold and maintain Clinical Laboratory Improvement Amendments of 1988 (CLIA-88), SAMHSA and CAP certification as well as any applicable state licensure.
Employers can test for a wide range of drugs Drug Class Screen Cut Off Confirmation Cutoff Amphetamines 150 ng/mL ?120 ng/mL Cocaine 15 ng/mL 6 ng/mL Marijuana (THC) 3 ng/mL 1.5 ng/mL Methamphetamines 120 ng/mL 120 ng/mL Opiates 30 ng/mL 30 ng/mL* Phencyclidine (PCP) 3 ng/mL 1.5 ng/mL

That's a very sensitive test, and as I suspected, they will confirm results with GC/MS, although (don't know if I mentioned this initially) EI or EIA as they put it, will most certainly catch it the first time around.

Let us know the results, I'm curious if you'd pass a test like this one.

If they do a GC/MS test on your sample, it will show every substance that has any trace metabolite in your body.

Those tests are much more sensitive, so yes, it's likely that they could miss the THC on a simple urine test, but it would show up with a more sensitive GC test!

I would keep your Resume handy. Weed stays in your system for 7 days, no exceptions, and is detectable through your hair follicles, saliva, blood, and urine. You did your best to think ahead. Now we need to think of what you'll tell them when they call you about it. Tell them you have chronic back pain, and that you smoke it in the evenings because it is the only thing that helps. Apologize and say you'd see a doctor for an alternative treatment for your pain. If that doesn't work, let the job hunt commence. Sorry about this shit man it really sucks.



yesI have passed a week after smoking when I was only a once in a while smoker and with the help of a cleanse I passed two days after my last joint as a daily smoker. It will vary somewhat depending on your own countries testing standards but in the US and Canada the piss test will not show after about a week of being clean unless they do a blood test or are using a very low level of THC to blood ratio.

I regularly smoke the night before swab tests. As long as you are sober when you take it you should be okay.

Thanks guys! I live in Melbourne and cops are insane about their booze and drug busts around here so I was a little paranoid. Thanks again :)

yesMy girlfriend got blazed one night, took a swab test directly the next morning, and it was cleared.
But again, it varies a lot. I'd say better safe than sorry, and I'd personally wait at least 48-72 hours. But I'm a cautious person. :)

Note :  Could be that the employer choose tests that don't give positives unless you're way over ,which should be the case.

From my experiences and research, a saliva swab will usually turn out negative from anywhere between 3-4 hours after inhaling depending on tolerance. After 5/6 hours you should be definitely fine. Luckily THC leaves your saliva pretty quickly.

yesI'm also pretty paranoid about driving after a session, but I know that after 4/5 hours I should be fine for a swab. I don't know which state you live in, but here in WA it's pretty uncommon to do routine swabs unless it's a booze bus late at night around a dodgy suburb. You should be fine to drive during the day and not worry about it! Good luck!


420EvaluationsOnline:  Californians that are not in perfect health may apply for a medical marijuana card online.  The process takes only a few minutes and there is no fee to apply.  A licensed physician evaluates your file and may recommend medical marijuana under the medical guidelines specified in State law (updated in 2018).  420EOL documents are used to purchase cannabis and derivative produces at about 25% less than recreational users from dispensaries, cannabis clubs, and at other points of access in the State of California and in some precincts in Nevada.

yesHey I'm from WA and one thing I can tell you about these tests is that they are not the most reliable things, I've had mates tested ~30 mins post toke completely high and showed up negative. I've heard from multiple people that simple mints and gum inhibit these tests from showing proper results. Head into the chemist get some clear eyes and some eclipse spearmint and have a bit of both. Everytime you drive, and you should be all sweet. I personally haven't been swabbed yet but I have been RBTd when very stoned.

My favourite trick that my friend told me is when they ask you if you have been taking anything, always say you had 1 beer about an hour or so ago. This works for a couple of reasons, the first is, If you have red eyes, it can be blamed on the beer. The second is, this really pulls the suspicion off weed, they will no doubt test your breath after for alcohol, but there will be none, and they can attribute any weird behaviour or nervousness to the alcohol and then when it comes back .00 they think, OK this person has been drinking but they have been honest and waited the right amount of time before driving again.


yesyesThe only other thing I can say is, drive safe, don't pump music too loud, and I doubt you will even get noticed, unless it's a booze bus checking everyone.




Man on the Street - Knows about what he's talkin




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