How to Dispute a False Positive Drug Test

Have you failed a drug test that your employer or a potential employer required? Do you believe that your results are incorrect? If yes, you should know how to dispute a false positive drug test. You can take steps to argue the findings, such as establishing why you received a false positive result. You might also ask the employer to re-test.

In this post, we explain drug testing in the workplace. We consider the likelihood of false positives and their causes, depending on the type of drug test. We’ll also examine what steps you can take to rectify the situation. Employers must also understand these concerns. Please refer to our dedicated guide for more on what employers need to know about drug testing.

What Is a False Positive Drug Test?

Any test that indicates a positive result when it shouldn’t. Such a test may indicate that someone has drugs in their system despite a lack of evidence of recent use. During random drug testing, an individual who has never used illegal drugs could test positive. False positives can have a severe impact on employment opportunities. Some employers use drug testing as a pre-employment requirement. Others test continually after hiring to maintain drug-free workplace policies.

Due to various factors, these tests are not always accurate, even though they apply advanced science. Such tools include gas chromatography and mass spectrometry. Some medications and even foods can resemble drugs to these tools. These mistakes cause positive results even if the subject has not used any illegal drugs. A drug test can’t always distinguish between specific molecules in your bloodstream. They may look chemically similar to illicit drugs. False positives may occur for substances such as marijuana, amphetamines, opioids, and many others.

Medications That May Generate False-Positive Drug Tests

The good news is that predicting when a drug test might lead to a false positive is often possible. You should know beforehand what substances may flag positive drug test results. For instance, you may encounter issues using one of the medications listed here in some types of tests.

1. Analgesics/NSAIDs

Some painkillers and NSAIDs (Nonsteroidal Anti-inflammatory Drugs) can cause false positive test results. These include some common “over-the-counter” pain relievers. Examples include Advil and Aleve. These drugs may cause a subject to test positive for THC, PCP, or barbiturates. Arthritis drugs such as Daypro can cause false positives for benzodiazepines.

2. Antibiotics

Some antibiotics can cause a false positive test for opiates. Examples include Cipro and Levaquin, often prescribed to treat various infections. If you’re completing an antibiotics course, inform the lab collecting your drug sample during the screening test.

3. Antidepressants

Prozac, Effexor, and other common antidepressant drugs can cause false positives, too. These prescriptions may appear on a drug test as LSD or amphetamines.

4. Antihistamines and sleep medications

Antihistamines are medications that treat allergies or hay fever. These drugs, such as Benadryl, will sometimes show false positives for methadone or PCP. Some sleep medications will have the same impact on drug screening. Diphenhydramine, better known as Benadryl, may cause a false positive.

5. Central nervous system (CNS) stimulants

Prescription medications that treat ADHD, such as Ritalin or Adderall, can lead to positive results for opiates and amphetamines.

6. Cough suppressants

Cough syrups are a medication for the common cold. They can also cause false positives in drug testing. The active ingredient in many over-the-counter cough suppressants is dextromethorphan. The drug testing process may identify this ingredient as an opiate or PCP.

7. Decongestants

Sudafed is another common cold medication. Its active ingredient, pseudoephedrine, can play a part in the production of methamphetamine, and it’s no longer an over-the-counter drug. Customers can still buy these products without a prescription, but a controlled process exists due to its side effects. Consumers must go to the pharmacy counter, show their photo ID, and sign a ledger as the precautions aim to curb meth production.

8. Proton pump inhibitors

Some medications that treat acid reflux disease and digestive conditions can lead to false positive drug tests for marijuana, including the popular OTC and prescription drug Nexium.

Substances That Can Trigger False Positive Drug Tests

Medications aren’t the only substances that can produce a false positive on a test for drug use. Several other elements can cause problems. Some or all of these might be in your medicine cabinet or kitchen and include:

1. Vitamin B supplements

Vitamin B2 (riboflavin) is beneficial for healthy body growth, the production of red blood cells, and more. It can also cause you to fail a drug test. Some riboflavin or B2 supplements come from hemp seed oil. Hemp seeds are part of the marijuana plant. As a result, some B2 vitamins can cause a false positive for marijuana use.

2. CBD (cannabidiol)

CBD is also derived from marijuana. People use CBD for many things, such as pain management or as a sleep aid. CBD has gained immense popularity in recent years. While it is non-psychoactive and cannot get you “high,” it still originates from a similar plant. As such, it could still put traces of THC in your bloodstream or urine sample, causing a failed drug test.

3. Poppy seeds

One of the most well-known causes of a false positive drug screening is the poppy seed. This topping is common on muffins, bagels, and other foods. However, poppy seeds come from the same plant used to make opium. Consuming poppy seeds before a drug test can lead a subject to test positive for an illicit drug.

4. Mouthwash

These products may contain alcohol. When you use them consistently, they can leave trace amounts of alcohol in your bloodstream. In most cases, there is nothing to worry about: standard drug tests don’t test for alcohol. If a subject needs an alcohol test and shows zero traces of alcohol in their body, these products can potentially cause problems.

5. Tonic water

Tonic water, a common ingredient in cocktails, can lead to a false positive drug test. It contains quinine, initially developed as a drug to treat malaria. Quinine only appears in tonic in low quantities, so it usually isn’t a problem. However, it has the potential to trigger a false positive drug test result for opiates. Copious consumption could cause such a result.

How Can I Dispute a False Positive Drug Test?

Are you concerned that you’re at risk of a false positive drug test? Do you believe you’ve already failed a drug test based on a false positive? Take the following steps to seek a resolution for the issue.

Step 1: Get ahead of the issue

Notify the lab or medical official conducting a drug test of potential problems beforehand. For example, do you regularly eat poppy seeds or take B2 supplements? Do you take CBD? If so, you should alert the testing agent before you submit a sample. If you have documentation to support your claim, provide it. These steps could help you avoid a false positive.

Step 2: Ask your doctor or pharmacist

If you’ve already failed a drug test, consider what might have caused the issue. The most critical step here is self-reflection. Think about what you’ve consumed recently. Review everything that could be to blame, including food, drink, and medication.

If you did take a medication in the days leading up to the drug test, ask your doctor or pharmacist if that could cause a false positive. If they concur, they can vouch for you with a prospective employer.

Step 3: Ask to retake the drug test

If you can, offer strong evidence for why your positive drug test might have been a false positive. Ask for a second test. For instance, if you apply for a job and are a strong candidate, you may receive a conditional job offer. That offer might be partially contingent on your drug test result. If you explain the potential circumstances, that employer should let you test again for the correct results.


Can you sue for a false positive drug test?

In recent years, many individuals have sued testing laboratories over false positive results. These cases usually allege improper procedures or a lack of due diligence. For instance, there have been cases where plaintiffs lost jobs due to false positives. They subsequently sued the labs for inaccurate results—and some won.

What can cause a false positive in a urine drug screen?

Some medications, CBD, and poppy seeds, contain substances that could trigger false positives on a drug test. These items have ingredients or origins in common with the drugs that labs need to detect. For instance, CBD oil comes from the cannabis plant. Using CBD can lead to a false positive for marijuana.

Can you fight a failed drug test?

Yes. Statistics show that false positives occur five to 10 percent of the time. There are enough substances that can cause false positives, making it always worth exploring the prospect of contesting a failed drug test.

What happens if a drug test comes back positive?

Do you need to know how to dispute a false positive drug test? The answer to this question depends on your situation. If you are in talks with a prospective employer for a new job and fail your drug test, the employer may rescind your job offer. If you are already employed and fail a drug test, your employer may dismiss you. You may also face drug tests for housing, and a failed test could lead to the denial of your leasing application.

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Michael Klazema

About Michael Klazema The author

Michael Klazema is the lead author and editor for Dallas-based with a focus on human resource and employment screening developments

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