A drug test, also known as a toxicology screening, determines whether there are any illegal or prescription drugs in your system ,  such as in your urine, blood, saliva, sweat, or hair. However, every so often, you might get a false positive drug test in return. 

There are plenty of reasons why you may be legally required to do a drug test. The most common reasons are to ensure a safe work environment, to monitor your health and performance on the job, or for legal purposes.

Regardless of the reason why you are required to have a drug test done, it is common to worry about the possibility of getting a false positive drug test.

In this article, we will disclose what causes a false positive and how to prevent it.

Factors that May Cause a False Positive Drug Test

Drug tests are designed to be quick and easy when it comes to collecting and analyzing biological samples. However, these tests can have limitations, which can cause both false positive and false negative drug test results.

The accuracy of the results depends on the type of drug and the type and quality of the test.

Factors that may interfere with your drug test and cause inaccurate results to include: medication, foods, hygiene products, and passive drug exposure.


Certain medications can affect your test results. Therefore, before doing a drug test, it is important to notify your healthcare provider if you have recently been taking any kind of medication or supplements. 

The medications that might interfere with your drug test results are antidepressants, antibiotics, analgesics, and antihistamines or decongestants.


The following antidepressants may interfere with drug test results when testing for methadone, and amphetamines or methamphetamines:

  • Venlafaxine
  • Trazodone
  • Bupropion
  • Sertraline
  • Clomipramine


Consuming antibiotics like quinolones can lead to false positive results when doing screenings for opiates. 


False positives may result for barbiturates, cannabinoids, and phencyclidine drug screenings when consuming analgesics like:

  • Naproxen
  • Ibuprofen

Antihistamines or Decongestants

In the case of drugs like opiates and amphetamines or methamphetamines, the following antihistamines or decongestants may cause false positive results:

  • Phenylpropanolamine
  • Brompheniramine
  • Diphenhydramine
  • Nonprescription nasal inhaler
  • Doxylamine


The following foods may cause false positives in your test results:

  • Poppy seeds (they have small amounts of codeine and morphine)
  • Cannabidiol (CBD) oil
  • Coca Tea (made of the leaves of the plant from which cocaine is extracted)
  • Hemp Oil

Passive Drug Exposure

Second-hand or passive inhalation of drugs like cannabis can show up in your drug test results as a false positive. However, unless you were exposed right before taking the test, it is unlikely you get a false positive result.

Hygiene Products

Hygiene products that contain concentrations of alcohol can affect your drug test results and lead to false-positives. Some examples include:

  • Oral hygiene products — such as mouthwash or breath freshener.
  • Hand sanitizer

What Happens if I get False Positive Results? 

If you get a false positive, the best thing you can do is notify your healthcare provider about any food or substance that may have interfered with your results.

After getting a false positive, the standard procedure is to do another drug test that confirms your results. 

Due to convenience purposes, when companies submit their employees to toxicology screenings, they prefer to use economic drug tests that provide quick results. Therefore, when having the second drug test done, it is likely to be a different kind of test than the first one.

Soteria Drug Screening provides high-quality tests to ensure the accuracy of your results. If you have any further questions about drug testing or another type of screenings, please reach out to us. We are here to help!

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