Used in clinical laboratories for the calibration and control of assays measuring 25-hydroxyvitamin D levels in human serum. It serves as a reference standard in diagnostic testing to assess vitamin D status, which is critical for evaluating bone health, calcium metabolism, and immune function. Commonly employed in liquid chromatography-tandem mass spectrometry (LC-MS/MS) and immunoassay platforms to ensure accuracy and consistency in patient test results. Also utilized in research settings to study vitamin D deficiency, supplementation efficacy, and related metabolic disorders.