Psilocin glucuronide in whole blood: a stable and useful biomarker of psilocybin intake
Journal of Analytical Toxicology February 19, 2026 Marianne Skov-Skov Bergh, Inger Lise Bogen, Merete Vevelstad et al.
A new LC-MS/MS method simultaneously quantifies psilocin, bufotenin, and their metabolites in human whole blood, using protein precipitation and lipid removal filtration. Psilocin degrades rapidly—46-66% at room temperature and 66-76% at 4 °C after one day, reaching 88-100% loss by three days; at -20 °C, up to 51% is lost after one month and ≥91% after three months. In contrast, psilocin glucuronide (PSG) remains stable for 14 days at room temperature and 4 °C, and for at least one year at -20 °C, making it a reliable biomarker of psilocybin intake. Bufotenin shows moderate stability, while 5-HIAA is unsuitable due to endogenous presence. Analysis of 23 forensic blood samples confirmed PSG in nearly all cases, even when psilocin was below the limit of quantification.