Review: No Scientific Basis for Concerns that CBD May Be Converted to THC Following Ingestion

Karlsruhe, Germany: Available science does not provide support for the possibility of in vivo conversion of CBD into either THC or its primary metabolites, according to data published in the journal Toxics.

A team of German researchers reviewed the relevant literature on the subject. They concluded: “[T]he in vivo conversion of CBD to Δ9-THC [is] not supported by the majority of the animal studies, where neither Δ9-THC nor one of its metabolites 11-hydroxy-THC and 11-COOH-THCA were detected in blood or in brain tissues. Adding to this, neither Δ9-THC nor any of its metabolites were detected after oral CBD administration in any of the human studies.”

Authors concluded that instances of subjects testing positive on a urine drug test for THC following the consumption of commercially available CBD products are a result of the products being tainted with THC – not because CBD is transformed in vivo to THC. 

Their conclusions are similar to those of prior studies – such as those here and here – reporting “no indication of human bioconversion of CBD to THC.”

Full text of the study, “Conversion of cannabidiol (CBD) into psychotropic cannabinoids including tetrahydrocannabinol (THC): A controversy in the scientific literature,” appears in Toxics. Additional information is available in the NORML fact sheet “FAQs About CBD.”