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Potential Triggers to a False Positive Drug Test

Drug testing has become commonplace for many employers before making a job offer, as well as at randomly selected times throughout the year. In addition, any time there is an accident while on the job, employees are required to submit to a drug test. For most people, taking the test is a minor inconvenience that has become a norm in work environments.

The increase in testing has brought into question the reliability of the test results, largely due to more employers doing their own onsite testing using over-the-counter screening tests and home test kits. It is not uncommon for a test to trigger either a false positive, or, in some cases, even a false negative result.

pharmacist medicine

What Is a False Negative Result?

A false negative result during a drug screening indicates the person passed the test even though there was the presence of some substance within their body. One of the most common reasons for a false negative result is because the drug test was used to screen for a specific substance rather than a broader range of substances.

For instance, parents who suspect their teenager is using drugs may only use a marijuana drug test while overlooking other types of drugs. If the teen is not using marijuana, yet is experimenting with other drugs, the test would give a false negative result and, potentially, mislead the parents into believing their child is drug-free.

In order to reduce the possibility of false negative results, tests need to be more inclusive and screen for all substances you want to include as part of a comprehensive drug screening. Parents do need to be careful when screening their teens using at-home drug test kits, as these are not always reliable and could actually result in a false positive result.

pile of medicine pills

What Is a False Positive Result?

A false positive result on a drug test means you did not pass it. It shows you failed some area of the test for one of several different types of substances or drugs. In recent years, and with scientific research, there are several different potential products on the market that could easily lead to a false positive test result.

For instance, poppy seeds are commonly consumed in a variety of foods, like bagels, breads, and so on. Yet, your daily enjoyment of a poppy seed bagel could result in a false positive on a drug test. How? Poppies are classified in the opioid family, which also includes a variety of illegal drugs. This could be unfortunate for you because consuming poppy seeds within a two- or three-day period before a drug test could result in a false positive result.

This is just one instance illustrating a single product. According to a research article published in The Journal of Family Practice, there is a host of products which can cause a false positive result on a urine drug test, presented in the following chart:


Amphetamine and methamphetamine Selegiline
Amphetamine and methamphetamine Vicks Inhaler
Barbiturate NSAIDs (ibuprofen, naproxen)
Benzodiazepine Oxaprozin
Cannabinoid NSAIDs (ibuprofen, naproxen)
Opiate Fluoroquinolone*
Opiate Rifampin
Phencyclidine Venlafaxine
Phencyclidine Dextromethorphan
*Ofloxacin and levofloxacin are most likely to cause false positives.


Urine tests are just one of a variety of testing methods. Other testing methods that are commonly used are hair follicle, blood, and saliva drug tests. These, too, can result in false positives. In addition to the above products, other items that have been known to alter the outcome of drug tests include:

  • Natural Herbal Supplements and Vitamin Supplements – Among the most notable are Vitamin B supplements, as the riboflavin used in them could be made from hempseed oil, which comes from marijuana plants and gives a false positive for THC.

vitamin supplements

  • Cold Medicines – Many over-the-counter cold remedies contain synthetic amphetamines, more commonly known as pseudoephedrine, which is also used to produce methamphetamines, a class of illegal drugs.
  • Tonic Water – If gin-and-tonic is your go-to drink, you could fail a drug test because tonic water contains quinine and causes tests to show positive for opiates.
  • Snack and Granola Bars – Some snack and granola bars contain trace amounts of hemp seeds. Depending upon the number of bars consumed, it could indicate THC on the test results.

snack and granola bars

  • Ibuprofen – Already mentioned in the above table as giving a false positive on a urine test for cannabinoids (i.e., marijuana), this over-the-counter pain reliever could also give false positive results for benzodiazepines and barbiturates.

Preventing False Positive Test Results

Employers need to take proper precautions when drug tests contain positive results. One common method is to perform a GS-MS (gas chromatography mass spectrometry) test to confirm the findings of the initial test.

However, in certain cases, a GS-MS test could still result in a false positive result. Employers need to keep in mind no test is 100% accurate, so they should not fully base their findings on a single test. Rather, using a combination of different testing methods, along with GS-MS, could provide more accurate results.

urine test


For individuals, there are several things you can do to help reduce the likelihood of failing a drug test. For instance, there are drug test detox products you can use when you are given advance notice of an upcoming screening. These products help remove impurities in the body that could contribute toward false readings.

Furthermore, for saliva and hair follicle tests, there are cleansing products you can use to rinse out your mouth, and shampoos to use to remove impurities from hair strands. In addition, it does not hurt to perform your own at-home drug tests periodically, just to be aware of potential false positive results.

In situations where you are not given advanced notice and are subjected to do an “on-demand” drug screening, it is in your best interests to provide a detailed list of items that could alter test results. Remember to include:

  • Over-the-Counter Medications and Pain Relievers
  • Cold Remedies
  • Vitamin Supplements
  • Herbal Supplements
  • Nutritional Supplements
  • Prescription Medications
  • Foods and Beverages Consumed, up to 72 Hours Prior to the Test

By providing this information, it lets testers know there could be the potential for skewed results and may lead them to reschedule the test or perform a GS-MS test first, rather than a standard drug test.

What to Do if You Suspect False Positive Results

Employers or their designated testing administrators should request that a follow-up test be conducted within a specified period to ensure initial test results were indeed accurate and not a false positive. Sometimes a different type of test should also be considered, especially if the current testing method is resulting in an excessive number of false positive results.

drug test lab

Individuals who know their test should have been negative should request a new test be performed after any foods, beverages, or products that could have altered the results can be properly flushed out of the body. For instance, if you have influenza with a cold, and a drug test is performed while you are ill, you could request the test be repeated once you are fully recovered from your illness.

Passing a Drug Screening

Tips for Passing a Drug Screening

If you are worried about an upcoming drug screening, it is worthwhile to consider reading more about various products and methods you can use to help pass drug tests, and to learn how to pass a drug test, like those available from us, here at ClearTest. To learn more about our products or assistance in selecting the best ones to use, do not hesitate to contact us directly by calling 1.800.248.5655 to speak with a representative today!




Contact ClearTest to learn more about how to pass drug tests.