Drug Testing Tips


-John Trever, Albuquerque Journal

California NORML’s Drug Testing Tips – Dealing With Urinalysis on Short Notice


While NORML strongly opposes drug use on the job, we think no one should be forced to submit to urine testing, especially for marijuana. Aside from launching a legal challenge, your best defense against urine testing is to be clean. Unfortunately, this may be difficult since urine tests may detect marijuana 1-7 days after an occasional use, 1-3 weeks in regular users, and up to 3 months in multiple daily users (more info). Since urine tests do not detect the psychoactive ingredient of marijuana, THC, but rather other, nonactive metabolites, they in no way measure impairment; nonetheless, this fact is of no account to employers in today’s anti-drug hysteria. If you are on the job market, it is prudent to expect being tested and avoid marijuana. However, recognizing that many of you may face drug testing on short notice, we offer the following advice for emergencies with our best wishes (but no promises!).

We are sorry having to mention these devious techniques, but feel it is necessary to defend innocent people against wrongful accusations of drug abuse. We urge you to use this information responsibly and not as a way of hiding irresponsible marijuana use.


Although urine tests are far from infallible, it is difficult to challenge positive test results. “False positives,” in which workers are wrongfully accused of drug use, are highly unlikely so long as labs exercise proper care (however, not all labs do this).

The Dept. of Health and Human Services has issued extensive mandatory guidelines for federal workplace drug testing programs (SAMHSA guidelines). They include safeguards to assure sample security, chain of custody, backup testing, and prevention of dilution and tampering. However, private employers do not regularly follow the SAMHSA guidelines, and even those required to do so are often derelict in following them diligently.

An essential safeguard in the SAMHSA guidelines is to to confirm all positive test results with a backup test. Samples are first screened with a so-called immunoassay test (e.g., EMIT or RIA). Positive samples must then be re-tested with the more accurate gas chromatograph mass spectrometer (GCMS). This virtually eliminates the chance of false positives in exchange for a relatively high rate of “false negatives,” where drug use is not detected. The sensitivity of the test is determined by the concentration of metabolites it is set to detect: for the DOT and other federal testing programs, the standard cutoff is 50 nanograms/milliliter (ng/ml) of marijuana metabolite (THC-COOH).

No commonly used substance is known to produce a false positive for marijuana. One exception is a prescription drug for ulcers known as Protonix®, which has been reported to cause a false positive for THC on immunoassay tests. Other prescription and over-the-counter medicines can cause false positives for amphetamine and other illicit drugs on immunoassay tests. However, all of these legal drugs can be distinguished from illegal ones using a backup GCMS test. It used to be that certain hemp foods could cause a positive for marijuana, but this problem has been fixed.

If you are taking a drug that might confuse a drug test, you are supposed to report it beforehand. SAMHSA guidelines require that positive drug tests be reviewed by a medical review officer (MRO), who will excuse legally prescribed drugs.

“Passive smoking” of marijuana is not an acceptable excuse at the 50 ng/ml level, since only in extreme circumstances can a non-smoker absorb enough pot to test urine positive (e.g., being stuck in a closet full of heavy smokers for hours). However, heavy passive exposure may result in positive tests at 25 ng/ml or lower. We do know of people who have flunked a drug test after accidentally ingesting a tainted brownie; unfortunately, this excuse didn’t impress their employers.


Although a growing number of states allow medical use of marijuana, they do not generally protect patients from drug testing. While some employers in medical marijuana states allow for medical marijuana, most do not, and those under federal regulations are specifically forbidden to do so. If marijuana were treated consistently with other drugs such as prescription amphetamines and opiates, medical users would be excused from positive drug tests if they had a doctor’s prescription. State law in this area is evolving. While the California Supreme Court has ruled that the state’s medical marijuana law does not protect patients from drug testing (Ross v. RagingWire), an Oregon appeals court has held otherwise. Further legal challenges seem likely as medical marijuana becomes more accepted.

One possible excuse for a positive marijuana test that sometimes works is a prescription for Marinol®, the FDA-approved synthetic marijuana pill that is currently available as a schedule 3 prescription drug. Marinol used to be indistinguishable from marijuana on both immunoassay and GCMS tests, creating a valid medical excuse for a false THC positive. However, some labs have begun to adopt a new technology that can distinguish Marinol from marijuana. Obnoxious as it may be for employers to fault employees for using marijuana instead of Marinol, use of Marinol can no longer be recommended as a technique for evading unfair drug tests.


The general strategy for passing urine tests is to increase your fluid intake and urine flow so as to dilute the concentration of drugs in the sample below the threshold of detection. An hour or two before the test, you should fill your bladder with a quart or two of water. Water is fine – contrary to popular rumor, there is NO evidence that goldenseal, vinegar, niacin, or vitamin C help. Many people wash themselves out for several days in advance by drinking a lot and exercising, but there is no reason to think this is useful. In no case should you give your first urine of the morning, since drug metabolites tend to build up during your sleep.

While you’re loading up on water before the test, you may also want to take a large dose (50-100 milligrams) of vitamin B-2, available in B-complex multivitamins. The purpose of this is to color your urine yellow, since otherwise you are likely to produce clear, watery urine, which makes some collectors suspicious.

Beware: Don’t drink too much, since labs are on the lookout for overly dilute urine. Dilution checks are required by the SAMHSA guidelines for federal testing . If your sample is found to be too watery, it will be returned as being too dilute. In this case, you may get a second chance to take the test.

For this reason, you should wait until your test results have been confirmed before indulging in compromising behavior.

You can boost your fluid output by taking diuretics, which stimulate urination. Weak diuretics include coffee, cranberry juice, certain health food products and over-the-counter pills for pre-menstrual water retention.

If you’re taking the test on very short notice, you may wish to resort to more potent diuretics, which are widely prescribed to treat high blood pressure. Although strong diuretics, such as furosemide (Lasix®), are available only on prescription in the U.S., they can be had over-the-counter in Mexico and other foreign countries. Beware that they can be dangerous for certain persons, such as diabetics or pregnant women, and can cause problems if taken over extended periods. Diuretics can be detected in urine, but are rarely checked except for athletes. The following regime has been suggested by a former army drug testing officer (Robert Freeman, “How to ‘Beat’ a Drug Test,” High Times, Aug. 1988): Take an 80-milligram dose of Lasix; take a hefty drink of water; piss two or three times, then take the test. If you’re lucky and didn’t smoke too much pot, a good washout may get you past a test on a couple days’ notice. However, regular smokers should allow more time if at all possible.


It has been suggested that the ingestion of certain substances might alter body chemistry so as to disguise drug use. Although many products are currently being marketed as drug screens in head shops, High Times ads, etc., they have no solid scientific basis. No screen has yet been proven effective in scientific studies. A number of high-priced herbal teas and powders are promoted as urine cleansers, with no good medical rationale. While some users have reported remarkable success with them, many others have not. Independent experiments suggest that it may be water dilution, not the screen itself, that accounts for success.


While urine dilution is useful, it isn’t 100% reliable, especially for heavy daily users. Another tack used by some people is to tamper with the sample by adding adulterants or substituting clean urine for their own. Ethical issues aside, tampering is risky since subjects may be observed or made to disrobe beforehand, and cheating isn’t forgiven. For the adventurous, the most reliable way to assure a good test result is to substitute clean urine, which is available from various internet vendors except in certain states that have banned its sale. Beware, however, that labs check to make sure the temperature of urine samples is right (around 90-97°F). Kits for delivering clean, heated urine may be found on the internet.

Another trick to foil the test is to spike the sample with an adulterant. This approach should be used only as a last resort, since any adulterant can be chemically detected if labs take the trouble to do so. A number of adulterants cause negatives on the commonly used EMIT test, but not necessarily other tests. All can be detected using appropriate lab procedures, but only if labs go out of their way to look for them. Common adulterants include detergent, bleach, and vinegar, but most of these are easily detected by smell, visual inspection or simple chemical tests. In emergencies, the least detectable household adulterant shown to be effective in foiling urine tests for THC is eyedrops (e.g., Visine®). A host of commercial adulterants are available on the market through the internet, mail order or head shops. Their formulations are constantly being changed to keep up with current detection technology. No additive is 100% reliable, and all involve a substantial risk of detection. Many drug testing companies claim to test for adulterants, but few do so consistently and thoroughly.

Many drug testing aids are advertised with money-back guarantees if you test positive. BEWARE: guarantees do not assure good test results! Vendors often exaggerate product reliability and ignore customer complaints.


In some situations, such as accidents, blood tests may be used. Blood tests are a much better gauge of current impairment than urine tests because they detect the actual presence of THC in the system; however, they can be used to measure non-psychoactive metabolites as well. Blood tests generally register positive for THC for just a few hours after smoking, but heavy chronic smokers may be positive at low levels for a couple of days. Blood levels of THC above 3-5 ng/ml are a sign of likely impairment. If you have used marijuana in the last few days but are not currently under the influence, you should insist on a blood test instead of a urine test if at all possible, since you are more likely to turn up clean. On the other hand, if you have smoked recently, you may do better to take a urine test, since this will at least leave open the question as to whether you were under the influence at the time of the test. Also, urine doesn’t turn positive until up to 3 or more hours after smoking for occasional users.


An increasingly popular but still unproven techology involves testing saliva taken from mouth swabs. Saliva testing has the advantage of being less invasive than either urine or blood tests. So far, tests have shown them to be inconsistent and unreliable when it comes to detecting marijuana, but that hasn’t stopped them from being used. The sensitivity of saliva tests hasn’t been clearly established, but may range from a few hours to a day or more. While it might be supposed that mouthwash is a helpful defense against saliva tests, this isn’t necessarily the case, since the tests are supposed to detect drug residues that are exuded from the body’s internal mouth tissues into the saliva.


One especially “Big Brother”-ish technology is hair testing, which can detect drug use for months, or however long one’s hair has been growing (Skinheads note: samples can be taken from any part of the body!). Obviously, hair testing has no bearing on current impairment, but only past use, since it takes more than a few hours for drugs to be incorporated into the hair. While hair tests are highly sensitive to cocaine, their sensitivity to pot is less well established.

One hair test study found that 85% of daily smokers tested positive, while only 52% of occasional smokers (1-5 times per week) did. Not all employers who use hair tests check for marijuana. Although the FDA and scientific community have been critical of hair testing, that hasn’t stopped employers from using it.

A number of shampoos are available on the internet that purport to be helpful in passing hair tests. At best, these may be slightly helpful in removing drug residues that are deposited externally on the hair by exposure to smoke. However, hair tests are supposed to detect drug residues that have been incorporated internally in the hair through the follicles, and which therefore can’t be washed out. In order to avoid false positives due to passive smoke exposure, laboratories are supposed to wash the hair themselves before testing it.


Prospective employees have no legal right to challenge pre-employment drug screens. However, workers who are already employed may be able to challenge their employers’ drug testing plans in certain situations depending on labor law and local regulations. Avoid signing anything that gives your boss the right to arbitrarily test you; by stating your objections, you will strengthen your right to refuse a test. If you think you are being unjustly tested, you may have cause for legal action. San Francisco, Berkeley and some other jurisdictions forbid on-the-job drug testing except in safety-sensitive positions.


A good source for the latest scientific information on drug testing is the Forensic Drug Abuse Advisor www.fdaa.com.
The California NORML Drug Testing Guide is a resource on:
• reliability of drug testing
• drug test detection times
• medical marijuana and drug tests
• drug tests and DUI
• dealing with drug testing on short notice
• what’s wrong with drug testing

The 44-page booklet combines the information on this page and the Guide to Interpreting Drug Test Results in an easy-to-read format, complete with charts, graphs and sources.


Many drug abuse clinics offer urine testing for a fee. Home test kits are available on the internet. Beware: drug urine levels can fluctuate up and down during the day, so it is possible to pass a test and then fail it a few hours later.



Privacy: Urine tests intrude on intimate bodily privacy. Mass drug screening violates the privacy of the majority of responsible employees in order to spot a minority of alleged drug abusers, many of whom are in fact not drug abusers at all. Government-imposed drug testing may be restricted by the 4th Amendment to the Constitution, which forbids unreasonable search and seizure and requires “probable cause” for search warrants. However, the 4th Amendment does not generally apply to tests by private employers.

Accuracy: No test is infallible. Surveys of drug testing labs have found remarkably high error rates from poor quality control. While good labs have added safeguards to minimize the risk of “false positives,” even if error rates are only one in 10,000, the extension of drug testing to tens of millions of workers as proposed by the government means that many workers will be falsely accused of drug abuse.

The most common misconception about drug urine testing is that it detects drug-impaired workers, whereas it actually detects evidence of past drug use that need have no relation to on-the-job performance. Because drug tests are highly sensitive to marijuana, random testing can promote use of other, more dangerous drugs such as cocaine and opiates, which wash out in 2-3 days, or LSD, which is rarely tested. At the same time, most drug tests totally disregard alcohol, the nation’s leading drug of abuse. Urine testing is tbus an inherently flawed technology: it rules out the most innocent off-the-job marijuana use, while permitting flagrant on-the-job alcoholiism.

Efficacy: Urine testing has never been scientifically shown to be safe or effective at improving workplace safety or productivity, and studies indicate that the great majority of drug-positive workers are just as reliable as others (John Horgan, “Test Negative,” Scientific American, March 1990; Dr. John Morgan, “Impaired Statistics and the Unimpaired Worker,” The Drug Policy Letter, May/June 1989). Medically, the consensus of expert opinion is that drug tests are an inherently unreliable indicator of drug impairment (Consensus Report, National Institute on Drug Abuse, Journal of the American Medical Association, Nov. 8, 1985). Dr. George Lundberg of the American Medical Association has called them “Chemical McCarthyism” (editorial, Journal of the American Medical Association, Dec. 5 1986).

The shortcomings of urine testing can be avoided through the use of impairment testing systems that use game-like computer tests. By measuring reaction time, decision making and hand eye coordination these tests screen for factors that cause employee impairment: fatigue, stress and illness.” Impairment testing for employees, and application for iPods and other devices, are available from and Bowles-Langley Technology (Alameda). A Hawthorne-based company, Systems Techology Inc. has also developed impairment tests.

Dale Gieringer Updated
January 2022
Copyright © 1997 CA