We are independent & ad-supported. We may earn a commission for purchases made through our links.

Advertiser Disclosure

Our website is an independent, advertising-supported platform. We provide our content free of charge to our readers, and to keep it that way, we rely on revenue generated through advertisements and affiliate partnerships. This means that when you click on certain links on our site and make a purchase, we may earn a commission. Learn more.

How We Make Money

We sustain our operations through affiliate commissions and advertising. If you click on an affiliate link and make a purchase, we may receive a commission from the merchant at no additional cost to you. We also display advertisements on our website, which help generate revenue to support our work and keep our content free for readers. Our editorial team operates independently from our advertising and affiliate partnerships to ensure that our content remains unbiased and focused on providing you with the best information and recommendations based on thorough research and honest evaluations. To remain transparent, we’ve provided a list of our current affiliate partners here.

What are the Different Causes of a False Positive Drug Test?

Tricia Christensen
Updated Jan 25, 2024
Our promise to you
WiseGEEK is dedicated to creating trustworthy, high-quality content that always prioritizes transparency, integrity, and inclusivity above all else. Our ensure that our content creation and review process includes rigorous fact-checking, evidence-based, and continual updates to ensure accuracy and reliability.

Our Promise to you

Founded in 2002, our company has been a trusted resource for readers seeking informative and engaging content. Our dedication to quality remains unwavering—and will never change. We follow a strict editorial policy, ensuring that our content is authored by highly qualified professionals and edited by subject matter experts. This guarantees that everything we publish is objective, accurate, and trustworthy.

Over the years, we've refined our approach to cover a wide range of topics, providing readers with reliable and practical advice to enhance their knowledge and skills. That's why millions of readers turn to us each year. Join us in celebrating the joy of learning, guided by standards you can trust.

Editorial Standards

At WiseGEEK, we are committed to creating content that you can trust. Our editorial process is designed to ensure that every piece of content we publish is accurate, reliable, and informative.

Our team of experienced writers and editors follows a strict set of guidelines to ensure the highest quality content. We conduct thorough research, fact-check all information, and rely on credible sources to back up our claims. Our content is reviewed by subject matter experts to ensure accuracy and clarity.

We believe in transparency and maintain editorial independence from our advertisers. Our team does not receive direct compensation from advertisers, allowing us to create unbiased content that prioritizes your interests.

There are numerous substances that can cause a false positive drug test result. Many of these are common medications that a number of people use while other substances are herbal treatments, foods or supplements that may cause a drug test to read improperly. Additional causes include testing or labeling errors or certain medical conditions.

As stated, one reason for a false positive drug test is laboratory error. Either the laboratory did not properly perform the test, or a labeling error occurred. Some labs are certified as drug testing labs and others are not, and some employers or other agencies performing drug tests don’t necessarily use a certified lab. If people can rule out all other potential causes of positive testing, they might be able to retake a test or redo it at a different lab, though this option isn’t available to everyone.

Undoubtedly, one of the main causes of a false positive drug test is using other medications. Some of those most indicated in false positive readings are over the counter cough and cold syrups, decongestants, and over the counter nasal sprays. Some prescription medicines used for pain relief or serious cough actually contain drugs like codeine, hydrocodone or oxycodone, and these may cause a true positive on very extensive tests or false positives on limited tests.

Antidepressants like Zoloft® or Wellbutrin® and antibiotics like Levaquin® and amoxicillin may cause false positive readings, and again, true positive readings could occur if people take drugs like tricyclic antidepressants, barbiturates, amphetamines, or benzodiazepines. These medications are legally prescribed for conditions like depression, anxiety, sleep problems, seizures, or attention deficit hyperactivity disorder. Similarly, some asthma medicines create inaccurate readings. A simple pain reliever like naproxen sodium may also read as drug use.

Herbal treatments and supplements may be reason for a false positive drug test. Several vitamin B supplements, anything that contains or is made from hemp, and substances like valerian or ephedra can affect drug testing. There are also foods such as the poppy seed, and any foods containing the supplements or natural substances above that might be an issue.

Some forms of liver and kidney disease have been linked to false positives. Those not taking any substances listed above, or eating any of the potential foods that can cause problems might want testing from their doctors to determine if an underlying medical condition exists. This could be used to challenge results.

In all, there’s an overwhelming list of false positive drug test causes. People awaiting drugs tests should keep a list of all medications/supplements they take and be ready to present information on legal prescriptions required for medical conditions.

WiseGEEK is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Tricia Christensen
By Tricia Christensen , Writer
With a Literature degree from Sonoma State University and years of experience as a WiseGEEK contributor, Tricia Christensen is based in Northern California and brings a wealth of knowledge and passion to her writing. Her wide-ranging interests include reading, writing, medicine, art, film, history, politics, ethics, and religion, all of which she incorporates into her informative articles. Tricia is currently working on her first novel.

Discussion Comments

By anon947771 — On Apr 27, 2014

I'm a diesel engine mechanic and my hair follicles test came back positive for methamphetamine and amphetamines and I don't take drugs. Please, can someone tell me how it was possible?

By anon92295 — On Jun 27, 2010

Can you answer on the flight attendant that has been turning up positive. She is battling custody and discontinue drinking. What can cause the elevation on the test?

Tricia Christensen

Tricia Christensen


With a Literature degree from Sonoma State University and years of experience as a WiseGEEK contributor, Tricia...
Read more
WiseGEEK, in your inbox

Our latest articles, guides, and more, delivered daily.

WiseGEEK, in your inbox

Our latest articles, guides, and more, delivered daily.