Running Title: Measurement of anandamide in human plasma Abbreviations: AEA, N-arachidonoylethanolamine (anandamide); AEA-d8, octo-deuterated anandamide; LOD, limit of detection; LOQ, limit of quantification; RSD, relative standard deviation; UPLC, ultra performance liquid chromatography, HPLC, high performance liquid chromatography; MS/MS, tandem mass spectrometry Keywords: anandamide, endocannabinoid, liquid chromatography, mass spectrometry, plasmaThe authors affirm that they have no conflicts of interest.