Keywords: 24,25-dihydroxyvitamin D3; 25-hydroxyvitamin D; infantile idiopathic hypercalcemia; LC-MS/MS; reference values The ratio 25(OH)D/24,25(OH) SB 2 sb D was calculated using 25(OH)D SB 3 sb and 24,25(OH) SB 2 sb D SB 3 sb . To the best of our knowledge, this is the first time reference values for 24,25(OH) SB 2 sb D SB 3 sb and the 25(OH)D/24,25(OH) SB 2 sb D ratio have been established with a method standardized using the NIST SRM 972a reference material. In conclusion, using a newly developed and standardized LC-MS/MS assay, we have established reference values for the 25(OH)D/24,25(OH) SB 2 sb D ratio in both men and women, aged 20-71 years. [Extracted from the article]