Since there is increasing evidence that postprandial hyperglycemia is a risk factor for the development of macrovascular complications, it is important to predict postprandial hyperglycemia in the early stages of glucose intolerance, and routine medical checkups provide a good opportunity to do so. The aim of this study was to evaluate the usability of 1,5-anhydroglucitol (1,5-AG) in routine medical checkups. The subjects were 77 Japanese men who participated in a routine medical checkup. First, we performed 75 g oral glucose tolerance tests (OGTTs), and examined the changes in glucose and 1,5-AG levels measured at 0, 30, 60, 90, 120, and 180 minutes (min). 1,5-AG levels did not significantly change until 90 min after the glucose load. Second, a linear regression analysis showed an inverse correlation between the 2-hour post-challenge glucose (2h-PG) and baseline 1,5-AG levels during the OGTT (P = 0.001, r(2) = 0.13), and the correlation was still significant after adjustment for age (2h-PG = 170 + 0.83 × (age in years) - 3.23 × (1,5-AG), P = 0.002, adjusted r(2) = 0.12). Finally, to investigate the test characteristics of 1,5-AG levels as a predictor of a 2h-PG level ≥200 mg/dL, we plotted a receiver operating characteristic (ROC) curve. The area under the ROC curve was 0.78, and the maximal sum of sensitivity and specificity (78% and 72%, respectively) was obtained at a 1,5-AG cutoff level of <14.2µg/mL. We conclude that 1,5-AG values may provide an ancillary predictor of 2h-PG of 75 g OGTTs in routine medical checkups.