Impact of CBD and hemp oil use on drug test results: a systematic review

BACKGROUND: Hemp-derived products, especially CBD (cannabidiol) oil and hemp oil, have shown a notable increase of use in recent years. CBD oil is a compound derived from the cannabis plant, whilst hemp oil is a product derived from hemp seeds. Trans-Δ9-tetrahydrocannabinol (THC) in cannabis is responsible for the psychoactive effect, whereas CBD, having the same molecular weight, is a non-psychoactive compound with analgesic, antiepileptic, antibacterial and anti-inflammatory effects. The rapid uptake of these products has raised concerns about unintended cannabinoid findings (THC, 11-OH-THC and THC-COOH etc.) on drug tests, especially in workplaces, road safety applications, and anti-doping programs. Although many CBD and hemp oils are marketed as “THC-free,” trace amounts of THC may be present in some products due to manufacturing variability, mislabeling, or contamination. These trace amounts may yield detectable levels in biological matrices or may cause cannabinoids findings. Regulatory frameworks for THC in cannabis products exist in several jurisdictions, but oversight of CBD-containing oils remains heterogeneous, creating gaps in quality control and labeling. METHODS: This systematic review aimed to evaluate whether the use of CBD and hemp oil may lead to cannabinoid-positive results in drug testing, potentially causing suspicion of cannabis use. The research design was prepared according to the PRISMA guidelines. The review included studies published in English between March 2014 and March 2024 that met the search criteria based on the keywords “psychoactive effects”, “forensic toxicology”, “THC positive”, “delta-9-tetrahydrocannabinol”, “delta-9-THC”, “test”, and “analysis” paired with the terms “CBD Oil” and “Hemp Oil” separately in the PubMed, WOS, and SCOPUS databases. RESULTS: The literature search yielded 477 results, 12 of which met the inclusion criteria. Eight of the 12 studies included evaluate of the possibility of positive cannabinoid findings or negative results in biological materials as a result of CBD and hemp oil use in humans. Five of these studies reported that the use of these oils would not create a positive result above the “limit of detection (LOQ) or cut-off levels” in the drug tests for THC. Although concentrations above the limit were not encountered, it is noteworthy, that trace levels or those close to the detection limits of cannabinoid levels were obtained. There are four studies designed to evaluate the conversion of CBD to THC in human metabolism after the use of oil products and two out of four studies emphasize that there will be no biotransformation or extraction-induced transformation after the use of CBD and hemp oils. CONCLUSIONS: This systematic review addresses current evidence on the occurrence and underlying causes of cannabinoid-positive drug test results following the consumption of CBD and hemp oils, highlighting critical gaps in analytical testing strategies and regulatory oversight. Positivity mainly arises from the product content (e.g., undeclared or excessive THC, mislabeling, and contamination), the matrix, the administration route, and the sensitivity and specificity of the analytical methods. The potential for CBD to convert to THC during manufacturing or in the human body may pose legal risks for individuals using CBD or hemp oil in countries with zero-tolerance policies.