Description General description 3-epi-25-Hydroxyvitamin D3 [3-epi-25(OH)D3] or (C3-epimer) is a metabolite of vitamin D3. It is an epimer of 25-hydroxyvitamin D3 which differs only at the C-3 position wherein -OH group at C-3 carbon is in the α orientation rather than in the β orientation. 3-epi-25-Hydroxyvitamin D3 (6,19,19-d3) is a deuterated vitamin D3 wherein C-6 and C-19 protons are replaced by deuterium. Application 3-epi-25-Hydroxyvitamin D3 (6,19,19-d3) can be used as an analytical standard for the quantitative analysis of 3-epi-25-hydroxyvitamin D3 content in biological fluids via LC-MS/MS. Packaging 1 mL in ampule