A test for CBD exposure can target the original compound or one of its metabolites. Pérez-Acevedo and colleagues measured four CBD metabolites in healthy volunteers after two cannabis preparations. Thirteen participants received a decoction in the first session and an oil after a 15-day washout.
In both sessions, 7-carboxy-CBD was the most abundant of the four metabolites measured in serum. It was followed by 7-hydroxy-CBD and the two 6-hydroxy forms. That ranking is relevant when comparing assays. A panel that measures only one hydroxy metabolite answers a different question from one that also measures the carboxy metabolite.
The investigators also collected urine, which provides a separate record of excretion. The serum ranking cannot be used as a universal ranking for every specimen or time after exposure. Comparisons should account for the matrix, the named analyte and when the sample was collected.