how to dispute a false positive drug test

How Do You Dispute a False Positive Drug Test?

Have you failed a drug test that was required for your job? Do you believe that you fell victim to a false positive with the test? If the answer is yes, there are steps that you can take to dispute the findings of the drug screening, from figuring out why you might have received a false positive to asking the employer for a retake opportunity. 

In this post, we will explain drug testing in the workplace, the likelihood of false positives, the causes of a false positive drug test, and the steps that you can take to rectify the situation.

What Is a False Positive Drug Test?

A false positive drug screening is a drug test that indicates a subject is positive for drugs in their system even when that individual has not used drugs recently (or, in some cases, ever). Some employers use drug testing as a pre-employment step and on an ongoing basis after hiring to maintain drug-free workplace policies.

Due to a variety of factors, these tests are not always accurate. Certain medications, substances, and even foods can “confuse” gas chromatography mass spectrometry drug tests, resulting in positive drug detection results even if the subject has not taken part in illegal drug use. A drug test can mistake certain substances or molecules in your bloodstream for some of the illegal drugs that the tests are designed to detect, such as marijuana, amphetamines, opioids, barbiturates, cocaine, PCP, and benzodiazepines.

Medications That Can Show False-Positive Drug Tests

The good news is that it is often possible to predict when a drug test might leave you with false positives. For instance, if you are taking one of the medications listed below, know before your drug screening that these substances can cause false positive drug tests.

1. Analgesics/ NSAIDs

Certain analgesics or painkillers and NSAIDs (nonsteroidal anti-inflammatory drugs) can cause false positive test results. Common pain relievers, for instance—including Advil and Aleve—can cause a subject to test positive for THC, PCP, or barbiturates, while arthritis drugs such as Daypro can cause false positives for benzodiazepines.

2. Antibiotics

Some antibiotics can cause false positives for opiates. Examples include Cipro and Levaquin, which are often prescribed to treat a variety of infections, from sinus infections to urinary tract infections.

3. Antidepressants 

Prozac, Effexor, and other common antidepressant drugs can cause a false positive for illicit substances, including LSD and amphetamines. 

4. Antihistamines and sleep medications

Antihistamines are medications that treat allergies or hay fever. These drugs, such as Benadryl, will sometimes cause false positives for methadone or PCP. Some sleep medications will have the same impact on a drug screening, including diphenhydramine—the generic term for Benadryl. 

5. Central nervous system (CNS) stimulants

Medications that treat ADD and ADHD (such as Ritalin and Adderall) can lead to positive drug screening results for opiates and PCP.

6. Cough suppressants

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

7. Decongestants

Another common cold medication is Sudafed. Its active ingredient, pseudoephedrine, is also used in the production of methamphetamine—in fact, Sudafed is no longer a true over-the-counter drug. Customers can still buy products that contain pseudoephedrine without having a prescription, but they must go to the pharmacy counter, show their photo ID, and sign a ledger to do so. These precautions are intended to curb the production of meth, but they don’t stop pseudoephedrine from triggering false positives for methamphetamine on a drug test.

8. Proton pump inhibitors

Medications such as Nexium that treat acid reflux disease, peptic ulcers, and other similar digestive conditions can lead to false positive drug tests for THC or marijuana.

Substances That Can Show False Positive Drug Tests

Medications aren’t the only substances that can produce a false positive on a test for drug use. There are several other substances—some of which might be in your medicine cabinet, pantry, or refrigerator right now—that can cause problems on a drug test. These include:

1. Vitamin B supplements

Vitamin B2 or riboflavin is beneficial for healthy body growth, the production of red blood cells, releasing energy from proteins, and more. It can also cause you to fail a drug test because some riboflavin or B2 supplements are derived from hemp seed oil. Hemp seeds are part of the marijuana plant, meaning that some B2 vitamins can cause a false positive for marijuana use.

2. CBD (cannabidiol)

CBD is also derived from marijuana. Known for helping individuals with conditions ranging from pain to sleep problems to chronic anxiety, CBD has gained popularity in recent years. While CBD is non-psychoactive and cannot get you “high,” it can still put traces of THC in your bloodstream or urine, which can cause a failed drug test.

3. Poppy seeds

One of the most well-known causes of false positives on drug tests is the poppy seed. Common in muffins, bagels, and other foods, poppy seeds come from the opium plant, which means consuming them before a drug test can lead a subject to test positive for opioids.

4. Mouthwash or hand sanitizer 

These products contain alcohol. When you use them heavily or 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. However, if a subject needs to take an alcohol test and show 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. Tonic contains a substance called quinine, which is what gives it its bitter taste. Quinine was initially developed as a drug to treat malaria. While it only appears in tonic in low quantities, consuming a lot of tonic still has the potential to trigger a false positive drug test result for opiates.

How Can I Dispute a False Positive Drug Test?

If you believe that you are at risk for a false positive drug test, or if you think that you have already failed a drug test based on a false positive, you can take the following steps to correct the issue.

Step 1: Get out in front of the issue

If you regularly use certain medications or consume vitamin B2 supplements, CBD, poppy seeds, or tonic water, consider notifying whoever is drug testing you ahead of time. Getting out in front of the issue—and showing documentation of what you are claiming, such as a prescription from a doctor for a medication—will protect you from a potential false positive.

Step 2: Ask your doctor or pharmacist

If you’ve already failed a drug test and are trying to determine why you might have triggered a false positive result, the most critical step is self-reflection. Think about what you’ve consumed recently—including food, drink, and medication—that could potentially be to blame.

If you did take a medication in the days leading up to the drug test, ask your doctor or pharmacist if that medication could have caused a failed drug test result. If they say yes, they will be able to 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, you should ask to be tested again. For instance, if you are applying for a job and are a strong candidate—such as if the employer has already extended a job offer that was partially contingent on your drug testing—that employer will likely be willing to give you a second chance if you explain the situation.


Can you sue for a false positive drug test?

It’s become more common in recent years for individuals to sue drug testing laboratories over false positive results. For instance, there have been cases in which plaintiffs lost jobs due to false positives and subsequently sued the labs for inaccurate results.

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

Certain medications, CBD, poppy seeds, and even tonic water are some of the substances that can trigger false positives on a drug test. These products and substances have ingredients or origins in common with the drugs that labs need to detect. For instance, CBD oil is derived from the cannabis plant, which means that using it 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 a false positive that it is always worth exploring the prospect of contesting a failed drug test.

What happens if my drug test comes back positive?

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

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