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Why CBD could cause a false positive on a drugs test

Why CBD could cause a false positive on a drugs test

Drug testing has become commonplace over the past decade. The most popular of which, is the urine drug screens. This is due to the ease of sampling, simplicity of use, and access to rapid results.

With the introduction of CBD products onto the global market, more and more consumers are asking if they will fail a drugs test after using CBD. However, in order to best answer this question, it is imperative that we first understand what CBD is and how a urine drug test works.


What is CBD?

Cannabis sativaL (hemp) and Cannabis Indica (Marijuana) are extremely versatile with applications ranging from construction materials, and textiles, to medicinal, and recreational uses. This may all sound straight forward, so why in reality is their so much confusion around marijuana and hemp?

The confusion is due to the word cannabis which is the umbrella term used to describe both hemp and marijuana plants - two different varieties of the cannabis genus. While both marijuana and hemp can be described as cannabis as they do share many similar features, they also have specific and distinctive differences.

The primary difference between the two is that hemp is nearly void of THC. In fact, in order for a cannabis strain to be classified as hemp in the United Kingdom, the strain must contain less than 0.2% THC. Hence, while it is generally true that CBD oil is THC-free, nevertheless it depends on the source of the cannabis that is used to produce the CBD oil, as some products do contain minute traces of THC. It must be said that these amounts are often so small that they do not even register above the minimum limit of quantification during 3rd party THC screening.

Researchers1 have recently discovered that the plant contains over 400 chemical compounds, of which around 80 are biologically active chemical molecules. The most important cannabis compounds are cannabinoids. There are approximately 60 different cannabinoids, the most significant psychoactive compound is tetrahydrocannabinol (THC), particularly Δ9-THC. Other identified compounds include cannabidiol (CBD), however, it is vital to note, in contrast with Δ9-THC, CBD is nonintoxicating as it does not present psychoactive activity, but rather exerts several beneficial pharmacological effects (National Library of Medicine - National Centre for Biotechnology Information: Jan. 2022).


How Do Drugs Tests Work?

According to a 2020 peer reviewed research article2, urine drug tests are based on immunoassay techniques and usually target substances such as alcohol, amphetamines, benzodiazepines, opiates/opioids, cocaine, and cannabis.

Immunoassay test use antibodies designed to attach to specific drugs or their metabolites — in this case, the presence of THC and its metabolites. If the antibodies identify a drug, they will produce a signal in the form of a “positive” test result. Although these tests do not screen for CBD, some CBD products contain low quantities of THC that, in theory, could lead to an individual failing a drug test.

It is worth mentioning that positive results from an immunoassay test should be confirmed with the GC/MS method (Gas chromatography/Mass spectrometry or high-performance liquid chromatography) in order to eliminate a false positive result.

As urine testing typically only has a detection window of hours to days, accurate detection of drugs is one of the biggest challenges for clinicians especially substances that are so new that tests have not been developed to detect their presence accurately. A positive result simply tells a clinician that the individual had a detectable amount of a substance present during a certain window of time. This outcome does not usually indicate impairment as the effect of any particular substance nor that the individual has a substance use disorder.


So, if CBD only contains minute trace amounts of THC, then how can you fail a drugs test?

In order to reap the benefits of CBD you need to take it consistently and allow it to build up in your system, which may stimulate your endocannabinoid system causing it to react more to cannabinoids like CBD. That's why so many people use these products for everything from tired and sore muscles to a better night's sleep. Furthermore, as each of us have a unique biology finding the correct dosage ('Goldilocks range') for our own body can be a tricky undertaking (The UK Food Standards Agency recommends not exceeding a daily dosage of 70mg). As mentioned, because CBD contains minute traces of THC, consistent use of CBD will in turn lead to those small amounts of THC building up in the body.


How long does CBD and THC last in your body?

According to Dr Kelly Johnson-Arbor, a triple-board certified medical toxicologist and co-medical director of National Capital Poison Centre, the clinical impact of CBD can last for several days after use3. In fact, a 2020 study in the Journal of Analytical Toxicology revealed that individuals who had consumed a single dose of a standardised CBD product had detectable levels of CBD in their urine for four to five days after ingestion4. So, based on the half-life of the drug, it’s likely that detectable levels may be present for several days after use.

On the other hand, because THC is stored in the body’s fat cells, the length of time it remains detectable depends on several factors, such as:

  • frequency and quantity of CBD use
  • body fat percentage
  • metabolism and eating habits
  • exercise routine


Due to all these factors, it is difficult to set one single standard detection time period. Some estimate detection can be anywhere from two days to several months.


What other medication or food stuff can cause a false positive for THC?

Notably, a false positive test result for cannabis or THC can also occur if an individual is using other drugs, including:

  • ibuprofen, naproxen, and sulindac dronabinol (nonsteroidal anti-inflammatory drugs (NSAID's)
  • pantoprazole
  • efavirenz
  • vitamin B supplements
  • snack bars

According to a study completed by Rollans et al5 published in the Oxford Academic - Clinical Chemistry, NSAID's reportedly caused false-positive results for THC (marijuana) in EMIT and other assay drug testing systems. Something as harmless as ingesting 12000 mg of ibuprofen can cause a drug test to show up as positive for barbiturates, benzodiazepines, and THC (marijuana). From this study Rollins et al5 concluded that NSAID's interfere with the enzyme on the EMIT tests, thus causing false positive results.

Pantoprazole and Efavirenz have also been known to cross-react with cannabinoid immunoassays leading to false positive test results. In fact, Efavirenz has been extensively reported in literature to cause false positive results for THC.

Vitamin B riboflavin, or B2 is often created from hemp seed oil. Like hemp seeds, hemp oil contains minute traces of THC and is likewise capable of causing a false positive test result.

The same can be said for granola and snack bars which contain hemp seeds for extra protein. These too contain tiny traces of THC which may cause a false positive drugs test. However, you would need to eat a fairly large amount of hemp seeds to fail your test.



While urine drugs tests are a valuable tool in the workplace, and for health care it does not test for CBD because it is not an illegal substance, nor does it give an intoxicating effect.

Immunoassays are presumptive only as external factors can influence their results. A confirmatory GC/MS method test should be performed before decisions are made based on results from a urine drugs test.

Furthermore, clinicians performing these tests should request detailed medication histories from test takers, including prescription, non-prescription, and even any herbal medications. It is also critical that they familiarise themselves with medications which have the potential to cross-react with urine drugs tests. 

Accurate interpretation of the authenticity and trustworthiness of these tools is critical especially when one considers that inaccurate interpretations of these tools can have serious social and legal ramifications.



  1. Iffland, K, Grotenhermen F. An Update on Safety and Side Effects of Cannabidiol: A Review of Clinical Data and Relevant Animal Studies. Cannabis Cannabinoid Res. 2017;2(1):139 - 154. [PubMed: 28861514]. Davies   C, Bhattacharyya S. Cannabidiol            as a potential treatment for psychosis. Ther Adv Psychopharmacol.      2019;9:20245125319881916. [PubMed:31741731].
  1. Caporuscio Pharm D. Can CBD make you fail a drug test?. Medically reviewed by Dr. Chen J. 2020; 1 - 5[Pub: MedicalNewsToday].
  1. Forbes Health, 16 June 2022, "How long does CBD stay in your system". https://www.forbes.com/health/body/how-long-does-cbd-stay-in-your-system/
  1. Spindle T, Cone E, Kuntz D, Mitchell J, Bigelow G, Flegl R, Vandrey R. Urinary Pharmacokinetic Profile of Cannabinoids Following Administration of Vaporized and      Oral Cannabidiol and Vaporized CBD-Dominant Cannabis. Journal of Analytical        Toxicology. 2020;44(2):109-125.
  1. Rollins DE, Jennison TA, Jones G. Investigation of interference by nonsteroidal anti- inflammatory drugs in urine tests for abused drugs. Clin Chem. 1990; 36:602-606.




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