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Can taking CBD make me fail a drug test?

Users of CBD oil have reported some benefits that have impacted their health. CBD oil has been used to help with anxiety, manage chronic pain, and aid with insomnia. With these incredible advantages, it is easy to see why it is becoming a popular method of treatment. However, due to its connection to THC, many people worry that CBD oils can make them fail a drug test. 

Is it possible though? The bottom line is that CBD will not show up on a drug test if you are using CBD isolate products that contain only the pure CBD compound. However, if you are using full spectrum products, there is an very small chance you could get a positive result. This is due to the fact that there are trace amounts of THC in full spectrum oils which can build up with use. 

This can also happen with products that contain other cannabinoids, like CBN, which could potentially show up too. To reach this level of testing, however, you would have to be consuming incredibly high amounts of CBD oil.

For THC to show up on a drug test purely from the use of CBD oil, the test would have to be very sensitive. If you're concerned with getting a false positive on a drug test due to the use of full spectrum CBD products, it might be worth explaining to your employer that you rely on them in advance. Here is our guide to understanding CBD and drug tests, and what to do if you have one coming up. 


CBD Oil and Drug Tests

Ultimately, CBD products containing just CBD isolate cannot make you fail a drug test but those with traces of THC have the potential of causing you to fail a drug test. Why is that though?

THC, otherwise known as delta-9- tetrahydrocannabinol is marijuana’s main active ingredient and is what causes users to feel inebriated or ‘high’. Drug tests are designed to react to THC. So, if you are using full spectrum CBD products, enough THC can cause a positive test depending on how you have consumed it and the quality of the product. 

CBD Oil Products and THC

CBD products aren’t regulated in the U.S. by the FDA (or the Food and Drug Administration) which makes it hard to know what is in them. Understanding where the CBD has been extracted from as well as how it is harvested gives you a greater understanding of how much THC contamination a product has suffered.

In the UK, laws are a bit different. The Medicines and Healthcare products Regulatory Agency (MHRA) have ruled that any products that contain CBD that are being used for medicinal purposes are a medicine. This means they have to have a product licence allowing them to be sold legally, supplied, or even advertised unless they have been made exempt from this. 

The UK also impose incredibly strict rules on THC content. If you are a resident within the UK and using products sold here, the THC content will be less than 0.2%, so you will have to ingest a huge amount of CBD oil for it to show up on a drug test.

Types of CBD

What type of CBD product you have consumed can influence if it makes an appearance on a drug test. CBD oils and tinctures have hundreds of naturally occurring compouns that aid in the absorption of CBD. The variety and strain of the plant will determine the chemical composition. Some of these compounds include: 

  • Flavonoids
  • Cannabinoids
  • Terpenes 

Marijuana plants are rich in THC, whereas hemp plants are devoid of THC, bar trace amounts and contain plenty of CBD. America requires hemp derived products to contain less than 0.3% in comparison to the UK which is even stricter, requiring 0.2%. This means that hemp-derived CBD will contain much less THC content than marijuana-derived CBD. 

How CBD is refined and harvested can also have a lasting impact on what compounds appear in your CBD. There are a variety of CBD extracts that have different ingredients. They are known as full-spectrum CBD, broad-spectrum CBD, and CBD isolate. 

Full-spectrum CBD

The CBD most likely to make you test positive on a drugs test for THC is full-spectrum CBD. Full-spectrum CBD contains all the compounds that are found in the cannabis plant. Some of these extractions include CBD, terpenes, THC, flavonoids, and other cannabinoids. 

Usually taken from marijuana subspecies, full-spectrum CBD products contain varying amounts of THC. If is marijuana-derived CBD, it could contain high amounts of THC. By law, however, hemp-derived CBD oil will have to contain less 0.3%THC in the U.S. or 0.2% in the United Kingdom. 

While manufacturers are legally required to disclose where they derive their full-spectrum extracts come from, many smaller scale CBD businesses don't making it harder to determine THC content in certain products. Despite this, they are widely available for purchase in the form of edibles, tinctures and oils, pastes, and topicals. 

Broad-spectrum CBD

Like full-spectrum CBD products, broad-spectrum CBD products contain additional compounds found in the plant, including terpenes and other cannabinoids. In comparison though, broad-spectrum CBD has all of the THC removed from its chemical structure. 

Due to this, broad-spectrum CBD products have less of a chance to contain THC than full-spectrum CBD products. Broad-spectrum products don't share the same popularity as full-spectrum products as many people believe in the entourage effect that full-spectrum products bring. They are however perfect for those who may be concerned about consuming even trace amounts of THC. 

CBD isolate

Considered to be pure CBD, CBD isolate doesn’t have any additional compounds from the cannabis plant that it was extracted from. Usually derived from hemp plants, hemp-based CBD isolate will not contain any THC. 

Often sold as a crystalline powder or a small slab that can be broken apart, it is commonly mixed into carrier oils to make a tincture. 


How Much THC Needs to Be Consumed to Show on a Drug Test?

So, you understand that THC can trigger a positive result on a drug test but how much needs to be consumed for it to show up and what exactly does it screen for? Firstly, if you take a drug test, it will be screening for THC or one of its main metabolites, THC-COOH. 

In 2017, the Mayo Clinic Proceedings ensured that federal workplace drug testing ensured values were established to prevent trace amounts of THC or THC-COOH triggering receptors that would declare a drug test positive. 

This would ensure that, even if you were taking full spectrum CBD, the amount of THC that would be found in your body would register your test negative. It should be noted though that different testing methods have different cut-off values and detection windows. Some of these testing methods are thorough hair, urine, blood, saliva, cross-contamination, mislabelling, and even second hand exposure to THC.


While a very uncommon testing process, there are no established cut-off limits for THC metabolites in hair currently. Some of the private industry cut offs include one picogram per milligram (pg/mg) of THC-COOH. To give you an idea in a measurement the lay person would understand, a picogram is about one-trillionth of a gram.

As is, THC metabolites are detectable in hair for up to 90 days, so it is something to consider if you know that you are going to undergo a hair test.



Arguably the most common form of testing, urine testing for cannabis is common and is done by most employers in the United States. To be found in a urine test, the metabolite THC-COOH must be present at a concentration of 50 nanograms per millilitre (ng/mL) to trigger a positive test. To put this into perspective, a nanogram is approximately one-billionth of a gram.

It is thought that THC metabolites can be detected anywhere from 3 days to 15 days after use. This detection window is varied due to dose and the frequency of use. THC has been found up to 30 days in the urine for those who are prolific users.


While blood tests are incredibly rare in cases of drug screening, it is good to understand how they operate. Workplace testing usually eliminates this method due to THC passing through the bloodstream rapidly. 

A blood test can be used to test impairment, so they are used as a solution for those who are possibly driving under the influence. While it is only detectable in plasma for five hours, THC metabolites can be detected for up to seven days. 


Another uncommon testing method, saliva tests have no established cut-off limits for detecting THC. Detectable in oral fluids for approximately 72 hours, it is thought to be detectable much longer if you are a heavy user of THC products. In 2017, the Journal of Medical Toxicology a suggested a cut-off value was discussed at 4 ng/ml.


Product Mislabelling

Not all CBD products are consistently regulated. This is becoming stricter, particularly in the United Kingdom, but many products don’t have a third party to test their composition. A study in 2017 conducted by Trusted Source tested 84 products that claimed to be CBD-only, hoping to find out the accuracy of labels for products bought online in the Netherlands.

Their research revealed that out of 84 products, 18 of them contained THC. This would suggest that product mislabelling is happening in the industry but, as it was such a small study, it should be noted that this might not be the case in other countries.

Second Hand Exposure to THC

It is very unlikely that you will achieve a positive drug test if you have been exposed to second hand marijuana smoke, but there is a very low possibility that it could happen. 

Research dictates that depending on the potency of the marijuana, as well as the size and the ventilation of an area, determines how much THC you will absorb. Something to bear in mind if people are smoking around you.

Can the Body Change CBD into THC?

Something that scares a lot of users is the question ‘can the body turn CBD into THC’? It is known that acidic conditions are able to turn CBD into THC, and this has led a lot of people to believe that the stomach is capable of this action in the body. In 2016, a study was conducted that simulated gastric fluid and managed to transform CBD into THC.

Don’t panic just yet, though, a study in 2017 found that this test didn’t present the conditions of an actual human stomach, and thus it was found that it wasn’t possible for CBD to transform in THC within our bodies. Another thing to note is that people who took part in these clinical trials to report the side effects of taking CBD were also potential THC users. 

Will Using CBD Isolate Make My Drug Test Positive? 

It can be stressful to take a drug test, even if you know you have nothing to worry about. If you are a CBD user, remember that these tests are designed to detect THC or one of its metabolites, so you won’t have any issues with a routine drug screening organised by work or other bodies. 

If you are worried and want to avoid THC exposure in all cases, ensure that you’re purchasing broad-spectrum CBD products from a reliable source like CBD Farmacy. If you’d like to learn more about the incredible benefits of CBD oil or need help picking out a CBD product be it, full-spectrum, broad-spectrum, or CBD isolate, get in touch today to see how we can help you. 


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