No products in the cart.

5 Things That Can Elicit a False Positive Drug Test

It is becoming more and more common these days for drug tests to be administered by a variety of authorities, such as schools, workplaces, and even hospitals. These types of administrators are commonly looking for what is known as a ‘drug of abuse,’ otherwise known as a drug misused for recreational purposes. 

Simply put, they are trying to weed out the people who’ve made smoking pot or using other substances part of their “lifestyle.” Reforming drug tests laws and standards is a hotly debated subject of marijuana activism, and people who classify themselves as cannabis enthusiasts largely agree that drug testing for marijuana in the workplace is unethical. It’s certainly unfair, especially considering that even certified medical marijuana patients can still be tested and penalized in most legalized states!

In this article, we will discuss what might trigger something referred to as a “false-positive” drug test result, an occurrence meaning some other non-illicit substances is causing the results to determine that you are abusing cannabis or some such drug. 

Can a Lab Drug Test Be Wrong?

For institutions or businesses that implement drug tests, a urine test, such as the iCup, if frequently used. These tests, although largely accurate, still have a 1-2.5% margin of error. These false-positives are often caused by the use of medical or non-recreational substances that carry similar chemical signatures to those for which the test is screening. So for those wondering if lab drugs can be wrong, the answer is: rarely, but yes. 

A petri dish can be used by a lab for testing for drugs , but can a lab drug test be wrong?

Medications That Cause False-Positive Drug Test Result

Substances, such as certain antidepressants and HIV medication, have been documented as causing positive results. Thus, it is crucial for both the test administrator and subject to establish what substances currently being used might cause a false-positive.

When it comes to screening in a drug test, most testers are looking for usage of specific drugs:

  • Amphetamines/methamphetamine
  • Cocaine
  • Marijuana/THC/Cannabinoids
  • Opiates/Heroin
  • Phencyclidine (PCP)

Most drug tests are accurate, but there are a few substances that would be best for you to look out for.

Will Cold Medicine Affect a Drug Test?

If you’ve been concerned about your NyQuil or other cold medicine will affect a drug test, you should proceed with caution. Some cold medications, namely pseudoephedrine, have been shown to yield false-positives when screening for amphetamines. This is mostly on account of the fact that pseudoephedrine is, in fact, an amphetamine. This doesn’t mean it’s inherently harmful, as many substances within the amphetamine family have medical applications.


Selegiline is primarily used with a combination of other drugs to treat Parkinson’s disease, however, it can also cause a false-positive on some drug tests. It should be well-documented in your medical history if you have been prescribed this drug, so if you get a false-positive for amphetamine use, it shouldn’t be a difficult issue to deal with.

Vicks Inhaler

Vicks inhalers are commonly used to treat stuffy noses and other cold symptoms, however, they contain compounds similar to amphetamines, which can cause a false-positive when being screened. 


Oxaprozin, also known as Oxaprozinum, or commercially as Daypro, Dayrun or Duraprox, is an NSAID anti-inflammatory drug used to treat pain caused by inflammation in joints and other areas of the body. This drug, however, also has a 100% false-positive rate when testing for Benzodiazepine. 


Fluoroquinolone is a fairly common antibiotic which is known commercially as  Gemifloxacin, Levofloxacin, and Moxifloxacin. Though it’s become less common in newer versions of the drug there is still a high chance it will cause you to test positive for opiate usage, it is yet another one to look out for. 

Can Turmeric Cause a False-Positive Drug Test?

A particular compound in turmeric called curcumin has been shown to cause some false-positives on drug tests. It doesn’t necessarily fill the slot for any particular substance, but the compound is so active within the body (many believe it has medicinal properties) that it can throw something of a chemical wrench in the proper functioning of a drug test, occasionally causing a false-positive. If you’ve got a drug test coming up, maybe skip the golden latte as turmeric can sometimes cause a false-positive drug test.

NOTE: Add a section to optimize for “What herbal supplements can cause a false-positive drug test?

What Can Cause a False-Positive Drug Test for THC?

Luckily, there isn’t a whole lot out there that will return a false-positive for THC. THC has a unique chemical signature, being one of the very few cannabinoids, or compounds that activates noticeable effects in humans. Namely, secondhand weed smoke has, on very rare occasions, shown a false-positive on drug tests, though it is far more likely for users of CBD, the other active compound in pot, to have a false-positive return. 

Some states allow THC levels of sometimes as high as 5% in CBD products sold legally in that state. While it’s not enough to get you “high”, the heavy consumption of CBD products has been shown to occasionally yield a false-positive test for THC. If you steer clear of any form of weed before a drug test for pot, though, you should be fine. 


With drug tests on the rise, it is important to stay informed about the failings of certain tests to keep yourself sane and sound when applying to jobs, schools, or even going to the hospital. We hope that the information in this article proves useful in helping you stay out of unnecessary trouble. 

Additional Readings on Cannabis Drug Testing and More

The Weed Blog: a place to find reviews of certain top strains of cannabis and online news resources regarding the legalization of marijuana. We are committed to helping you find valuable information about cannabis on our website. With the laws of marijuana constantly changing, learn about the latest laws here. Otherwise, consider these other top tier articles:

How Long Does Marijuana Stay In Your System? [Infographic]

Everything There Is To Know About CBD Skincare

Flower Power: Cannabis And The Culture Of The ’60s



Related Articles