Background & Aims: Serum 25-hydroxyvitamin D (25(OH)D) comprises 25(OH)D3 and 25(OH)D2. Although sex differences in 25(OH)D levels have been reported, it remains unclear whether the difference lies profiles of 25(OH)D. We determined serum 25(OH)D3, 25(OH)D2, 3-epi-25-hydroxyvitamin D3 (3-epi-25(OH)D3), (24R)-24,25-dihydroxyvitamin (24,25(OH)2D3) measured by LC-MS/MS healthy adults not consuming...