Abstract: Objective To investigate the relationship between fasting plasma glucose (FPG) and age/sex, and to further analyze the appropriate cutoff age for detecting hyperglycemia, providing a reference for blood glucose screening and health management. Methods Using a cross-sectional design, a total of 50,607 examinees from the Physical Examination Center of Shanghai General Hospital in 2023 were included. The age and sex distributions of FPG levels and the abnormal detection rate (FPG ≥6.1 mmol·L^-1) were analyzed. A non-parametric method was used to plot the receiver operating characteristic (ROC) curve for age in predicting hyperglycemia. The area under the ROC curve (AUC) reflected the predictive value of age for abnormal FPG, and the appropriate cutoff age for hyperglycemia detection was determined by the maximum Youden index. Results The median FPG (P₂₅, P₇₅) of the study population was 5.00 (4.68, 5.41) mmol·L^-1, with levels systematically higher in males 5.06 (4.73, 5.53) mmol·L^-1 than in females 4.93 (4.64, 5.28) mmol·L^-1. Both FPG levels and the abnormal detection rate increased non-linearly with age, plateauing after approximately 80 years old. ROC curve analyses showed that age had good discriminatory value for hyperglycemia status (AUC=0.778 for the total population), with the appropriate predictive age threshold being 48 years old (48 years old for males, 49 years old for females). Conclusion These findings provide an important basis for developing targeted screening strategies for key age groups and implementing stratified health management interventions. Specifically, the 45~50 years old period should be set as an intensified phase for blood glucose screening, with particular emphasis on earlier intervention for males. Glycemic management targets for the elderly population require individualized consideration.