CBD, or cannabidiol, is a non-intoxicating cannabinoid derived from hemp–it will not get you high. Since the 2018 Farm Bill, it is legal in the US as long as the THC content is <0.3%. Since CBD is legal, it is not usually tested for– the test is designed to pick up THC, the intoxicating or high-producing cannabinoid. However, since THC is very similar to CBD chemically, the tests may pick up THC either because the tests are not that sensitive or specific OR because your product contains enough THC (or you use it often enough) to show up on very sensitive tests. Read on for some of the important details on CBD and drug-testing.
However, it is important to remember that very few employers or any types of institutions test specifically for CBD. There is a small chance that using a full-spectrum CBD product may produce a positive test result, but it is not likely.
While both medical and “recreational” cannabis is legal in many states and CBD is legal in most states, employers can still refuse or fire from a job if an employee tests positive for one or more of several drugs. You can also be tested for drugs for legal cases, as an athlete and to monitor prescription drug use. The most commonly tested drugs include :
Most drug tests check urine samples, but hair, blood and saliva can be tested as well. Alcohol can be tested by a breathing sample or in a blood sample. The first five substances make up the most common 5-panel testing.
The tests used are some form of an ELISA assay– ELISA stands for Enzyme-Linked ImmunoSorbant Assay. The tests can consist of an ELISA assay, an EMIT (Enzyme Multiplied Immunoassay Test) or a CEDIA (Cloned Enzyme Donor ImmunoAssay). These are all automated and can also be used as a hand-held device. They are all based on the binding of a synthetically produced antibody to the substance tested.
Every testing method should meet minimum requirements– but every testing method has inherent problems. Some of these problems concern a test’s specificity the ability of the test to correctly identify the absence of a tested substance (to detect true negatives) and the test’s sensitivity, the ability of the test to correctly detect the presence of a substance ( to detect true positives). Another way to put it is that every test has some rate of false positives and some rate of false negatives. Increasing the sensitivity of a test getting true positives usually decreases the specificity of the test– getting more false negatives.
Another set of problems surrounds the concepts of accuracy and precision. Accuracy of a test refers to how close a test comes to measuring a true value while precision refers to how closely the result matches on repeated testing.
All lab tests can have problems with accuracy and precision and with sensitivity and specificity– some of the problems are inherent in the way a test is designed and the limitations of that design while other problems are dependent on outside factors including human error.
There is a limit to how much of any substance can be detected. In the Federal Workplace Drug Testing Program , the initial screening must detect at least 50 nanogram/mL of THC (or metabolites) in urine. The confirmatory test must detect at least 15 nanograms/mL of THC (or metabolites). If the initial screening comes up positive, there must be a confirmatory test.
For reference, a nanogram (ng) is one billionth of a gram or 0.000 000 001 grams.
Full spectrum CBD products can contain up to 0.3% THC. Broad spectrum CBD should contain significantly less THC while CBD isolates should contain no THC. Your greatest chance of testing positive for THC while using CBD products comes from using full spectrum products and your lowest chance of testing positive for THC is when using CBD isolates.
Remember, CBD is a legal substance in most states– and there are few if any tests used to specifically detect CBD. There are however THC tests. These can:
The half life (t1/2) of any substance is the time it takes for that substance to be metabolized or excreted from the body. The t1/2 of THC and CBD are complicated by the fact that both are fat soluble– you can “store” both THC and CBD in fat tissue and the longer you use any form of cannabis or CBD and/or the more you use either, the longer it can stay in your system. It also depends on how much fatty “storage sites” you have as well as how well your liver is able to metabolize either THC or CBD. There are no definitive numbers on this, though there are some reasonable estimates.  THC can be detected in urine samples for up to 15 days, depending on your “storage sites”, how much you use, the delivery method (eg. oral vs. smoking), how long you have been using and how well your liver metabolizes the THC.
On the other hand, CBD can remain detectable for up to 30 days– the actual number of days that it can last in your body depends on the same factors as for THC.
BUT– if you only use CBD and not THC and use only the full spectrum products, any THC in your system will probably be well below detectable limits within 5-7 days after the last use. There are no guarantees, however. If you know that you are likely to be tested for THC use, the only semi-guarantee is to not use any product that may contain THC for at least 2-3 weeks. It’s only a semi-guarantee because of the factors listed. You should also be aware that 2nd hand smoke or vapor may cause a positive test result.
Using either broad spectrum CBD products or CBD isolates likely reduces your chances of testing positive to minimal levels. Broad spectrum CBD products should contain little if any THC (but check the 3rd party lab tests) and CBD isolates should contain no THC at all.
In this case, the most likely way you would still test positive for THC is if the test lacks at some point for specificity, sensitivity, accuracy, precision or some human error occurred.
Overall, using only either broad spectrum CBD products or CBD isolates along with checking the 3rd party testing results (and maybe keeping these on hand just in case…) should reduce the chance of a positive drug test close to zero.
 Lucas, CJ., Palettis, P., Schneider, J. The pharmacokinetics and the pharmacodynamics of cannabinoids. Brit J Clinical Pharm., 84(11), pp 2477-2482, 2018. https://doi.org/10.1111/bcp.13710