Two people who take the same amount of psilocybin can have different blood concentrations of psilocin, its active metabolite. Jensen and colleagues studied this in 10 adults with severe alcohol use disorder. Each participant received one supervised 25 mg dose of psilocybin under the same treatment protocol.
Peak plasma psilocin concentrations ranged from 14 to 59 micrograms per liter, a little more than a fourfold difference between the lowest and highest observed peaks. Those values describe the highest concentrations observed for participants under the study’s sampling protocol. They do not describe concentrations at a single common time after administration.
For toxicology interpretation, the distinction matters in both directions. A known dose does not fix the concentration expected in one person, and a single concentration does not establish the dose. A comparison would need the time of collection, the specimen type and the assay’s target. This small study describes variability in a supervised clinical setting. It did not establish a plasma concentration threshold for impairment.