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Drug Test Adulteration

Adulteration in Urine and Oral Fluid Drug Testing

Adulteration in Drug Testing

The number of people using drugs keeps increasing worldwide. This increase in substance use is mostly due to mental health disorders and the legalization or decriminalization of drugs. This increase is even more concerning when it involves safety-sensitive employees. Several employee surveys reported high levels of stress, anxiety, depression related to job security, heavy workload and income. Employers implement workplace drug testing programs to protect employees from the impact of drugs and bring security and safety to workplaces. Drug testing is considered good practice for the prevention and limitation of both illicit and medicinal drug abuse (e.g. workplace drug testing, school drug testing, random road site drug testing). However, one of the major challenges of drug testing is adulteration.

Adulteration of Urine and Oral Fluid matrices

Adulteration is the manipulation of a sample with chemical adulterants or using other ways to generate a false negative result. Although companies strive to increase workplace safety and productivity, some employees still try to cheat drug testing.

Drug testing looks for parent drugs (administrated drugs) and metabolites (a by-product of the parent drug). A drug test can be performed in different matrices. Urine, blood and oral fluid are the most popular ones. Urine is the commonly used matrix for drug detection due to its ease of collection and relatively long detection windows. However, urine sample collection may be inconvenient and unreliable because of the need for collection facilities, same-sex observation and adulteration (dilution, addition of foreign substances and sample exchange). Oral fluid has fewer limitations as it can be collected using non-invasive sample collection techniques. This newly accepted matrix is not only non-invasive but also easy to collect and the oral fluid matrix enables recent drug use detection. Out of 27 EU countries, only 8 do not allow roadside oral fluid testing yet.

To clear themselves of drug use, people use various tricks to cheat drug testing. Tampering with a collected specimen to produce a false-negative test result is common practice. Millions of websites helping drug users cheat will pop up when you search the Internet for "cheat on a drug test", "pass a drug test", "beat the drug test", etc.

Adulteration can alter the result of an initial drug screening test, a confirmatory test or both. Urine is most prone to be adulterated. There are three different types of drug test adulteration:

  • Dilution (in vivo adulteration)
  • Substitution or sample exchange
  • Adding foreign substances (in vitro adulteration)

When testing someone, you may wonder: Has the sample been mixed? Was anything added to the sample? Has the sample been exchanged?

What is adulteration in a drug test?

When a donor intentionally seeks to interfere with a drug test result by altering the sample, this is considered adulteration.

In drug testing, a specimen or sample is identified as adulterated if it contains substances that are not normally found in the collected specimen (e.g. in vitro adulterants), or the expected substances are found at irregular concentrations (for example due to dilution). Adulteration is considered one of the major challenges of urine drug testing. The use of adulterants can cause false-negative results in drug tests by destroying the drugs in the urine or by interfering with the test itself.

A set of tests can determine whether a sample has been altered or substituted. Such tests are mandatory to avoid any false results. Without proper adulterant screening, even gas chromatography-mass spectrometry - an advanced analytical method that can identify even small concentrations of drugs - can be misled by an adulterated sample.

Common Ways of Cheating a Urine Drug Test

Dilution of urine specimens (in-vivo adulteration)

Taking large quantities of liquid is the most common form of adulteration and probably the most difficult to prove.

Urine substitution

Replacement of a urine specimen with that of a drug-free or commercialized synthetic urine sample.

In vitro adulteration

Adding in vitro masking reagents (chemical substances) into the urine specimen (e.g. household chemicals such as bleach, laundry detergent)

    Dilution of Urine specimens or In Vivo Adulteration

    Evidence of adulteration may be in the form of excesses of expected substances. An example of this type of adulteration would be excessive amounts of water present in a urine sample.

    Drinking large amounts of water and taking (or not) diuretic pills can help dilute urine. This type of adulteration is called dilution. It is used to increase the elimination of the drugs out of the body, to have, at the moment of drug testing, the concentration of the drug below the concentration sought by the test (cut-off levels).

    Common products are Absolute Detox XXL Drink, Absolute Carbo Drinks, Ready Clean Drug Detox Drink, Fast Flush Capsules, and Ready Clean Gel Capsules.

    In Vitro Adulteration

    After collection, external substances (in vitro adulterants) are added to the urine sample to interfere with drug assays. Both screening (based on immunoassay) and confirmatory (based on chromatography) analyses are susceptible to give false-negative results.

    A urine sample that contains a chemical additive not normally found in urine will therefore be considered adulterated.

    Oxidizing adulterants

    Some substances referred to as oxidizing adulterants can alter drugs in urine samples and make them undetectable by any testing technology, even for the advanced ones. Such substances can also interfere with the analysis performed on the sample itself. For example, nitrate can either act upon the drug testing method (e.g. in the case of benzodiazepines, cocaine detection) or on the drug itself (e.g. cannabis detection).

    Examples of oxidizing adulterants include Stealth (peroxidase and peroxide), Klear (nitrite), Clean ADD-IT-ive (glutaraldehyde) and Urine Luck (pyridinium chlorochromate [PCC]).

    Common Ways of Cheating an Oral Fluid Drug Test

    Some people try to cheat oral drug tests, often by:

    • drinking a lot of water
    • chewing gum
    • using detox drinks
    • eating breath mints
    • using cosmetics
    • using products sold specifically to interfere with the state of saliva.

    If the participant takes a detox drink right before the test, it can temporarily reduce the concentration of certain drugs in the saliva.

    Food and drinks can interfere with oral fluid samples

    To prevent food substances from causing false-negative or false-positive results, those undergoing testing are usually required to refrain from eating or drinking for at least 10 minutes (depending on the chosen oral fluid drug test) before drug testing.

    Our Synens OM90 oral fluid drug test requires not to drink, eat or smoke anything for at least 10 minutes before sample collection. Proper sample collections help to avoid false-positives (samples that test positive for the presence of drugs, but are not) and false-negative (samples that test negative for the presence of drugs, but are not).

    Food substances

    Common foods, beverages, food ingredients such as vinegar, coffee, spicy food, fruit juice, acidic juice, poppy seeds, etc.

    Hygienic products

    Mouthwash, toothpaste: hygienic products can clear off residual drugs of abuse compounds due to rinsing of the oral cavity.

    Testing for Adulterants in Urine

    Adulterants need to be detected in urine at the pre-analytical stage as many adulterants render immunoassay screening or chromatographic analyses ineffective. Laboratories use a variety of means to detect adulterants, starting with the observation of physical characteristics of the sample (e.g. colour, odour) and chemical analysis (e.g. creatinine or glutaraldehyde, pH) and ending with more advanced analyses (chromatographic techniques that can detect small concentrations of adulterants).

    An integrity test is performed by monitoring the temperature, pH, specific gravity and creatinine levels. A non-adulterated urine sample has a pH level of 4.0 to 9.0 with a temperature range around 32-38° C, specific gravity between 1.001-1.020 g/ml, and creatinine concentration higher than higher 20 mg/dL. A urine sample with a pH level, temperature, creatinine level, or specific gravity outside these approximative ranges is reported adulterated. Other laboratory tests include nitrate, glutaraldehyde, chromium, halogen, oxidant and surfactant testing. More advanced techniques of analysis can be used (immunoassays or chromatographic) to detect some adulterants (oxidants), but they are expensive to perform for routine drug testing laboratories.

    Nitrite tests

    Detection of nitrites in urine may be due to medication use such as nitroglycerin, isosorbide dinitrate, and nitroprusside, or a sign of a urinary tract infection (UTI). However, nitrites can also flag the possibility of drug test adulteration. A nitrate concentration greater than 200 mcg/mL, but lower than 500 mcg/ml is considered adulterated.

    Glutaraldehyde tests

    Glutaraldehyde is not normally present in urine. Therefore, the detection of this substance in a urine sample is usually an indicator of adulteration. Adulterants such as UrinAid and Clear Choice contain glutaraldehyde which can cause false negative results by acting upon the immunoassay.

    Although routine specimen integrity tests can detect most of the domestic adulterants, except for Visine eye drops and alcohol/isopropanol, adulterants containing strong oxidising agents such as potassium nitrite and pyridinium chlorochromate, or Stealth, require a different method.

    Testing for Adulterants in Oral Fluid

    There is less possibility of in vitro adulteration with the oral fluid matrix as oral fluid samples are collected under observation. The use of adulterants in oral fluid samples is, therefore, less likely. However, drug test adulteration is possible by rinsing the mouth with water or mouthwash, chewing gum. This practice causes an increase in saliva quantity. Drinking or eating can lead to a decrease in drug concentration. This is why it is required to supervise the donor 10 minutes before performing the drug test to prevent any adulteration attempts.

    However, a validity test is performed on the specimen to avoid any problems due to dilution of the oral fluid sample or the use of adulterants. This validity test determines the level of albumin and immunoglobulin G.


    (1) European Monitoring Centre for Drugs and Drug Addiction (EMCDDA). European Drug Report; 2020; p 88.

    (2) European Monitoring Centre for Drugs and Drug Addiction. Drug Use, Impaired Driving and Traffic Accidents: Second Edition.; Publications Office: LU, 2014.

    (3) OBSERVATOIRE NATIONAL INTERMINISTÉRIEL DE LA SECURITE ROUTIERE. La Sécurité Routière En France Bilan de l’accidentalité de l’année 2019; 2019.

    (4) Legal approaches to drugs and driving |

    (5) Reichardt, Eva M., Dene Baldwin, and M. David Osselton. 2013. “Effects of Oral Fluid Contamination on Two Oral Fluid Testing Systems.” Journal of Analytical Toxicology 37(4): 246–49.

    (6) Rohrig, Timothy P., and Christine Moore. 2003. “The Determination of Morphine in Urine and Oral Fluid Following Ingestion of Poppy Seeds.” Journal of Analytical Toxicology 27(7): 449–52.

    (7) Wong, Raphael C., Minhchau Tran, and James K. Tung. 2005. “Oral Fluid Drug Tests: Effects of Adulterants and Foodstuffs.” Forensic Science International 150(2–3): 175–80.

    (8 )Federal Register / Vol. 84, No. 207 / Friday, October 25, 2019 / Rules and Regulations, mandatory guidelines for federal workplace drug testing programs by agency Substance Abuse and Mental Health Services Administration (SAMHSA) for oral fluid testing

    (9) Federal Register / Vol. 84, No. 207 / Monday, January 23, 2017 / Rules and Regulations, mandatory guidelines for federal workplace drug testing programs by agency Substance Abuse and Mental Health Services Administration (SAMHSA) for urine testing

    (10) Dasgupta, A. 2007. “The effects of adulterants and selected ingested compounds on drugs-of-abuse testing in urine.” American Journal of Clinical Pathology 128(3): 491-503.

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