Analyte Q1 mass (Da) precursor Q3 product Dwell Time, ms. Collision Energy, V 25-OH d6D2 419.3 355.3 50 7 25-OH D2 413.3 355.3 50 7 25-OH d6D3 407.3 371.3 50 9 25-OH D3 401.3 365.3 50 8

Table 1: Quantification MRM precursor/product ion transitions selected for measurement of 25-OH D.