This article provides a systematic interpretation of two pivotal studies on the standardization of serum C-peptide measurement published in China in 2023. Addressing the significant variability in C-peptide test results across domestic laboratories, the research established an isotope-dilution liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS) reference method. This method demonstrated excellent performance, with precision ≤2.2% and accuracy (recovery rate) of 99.6%~101.0%, enabling traceability to SI units. Method comparison revealed substantial biases (32.2%~81.7%) in routine immunoassays, which were significantly reduced (to -6.0%~1.2%) after recalibration using frozen human serum pools (FHSP) assigned by the reference method. Furthermore, the studies identified FHSPs as candidate reference materials with satisfactory commutability and stability, offering a solution for the commutability issues prevalent in external quality assessment (EQA) programs. Together, these two studies construct a complete "reference method - reference material - standardization application" system, providing crucial technical support for improving the consistency of C-peptide measurement in China and holding significant importance for advancing precise diagnosis and treatment of diabetes.