Glycated albumin (GA) reflects shorter term glycemic control state than HbA1c. This study evaluated whether GA is useful for early detection of deterioration of glycemic control state after discharge from educational admission. Among the patients with educational admission, this study included 21 diabetic patients who were followed for at least 10 weeks after discharge from educational admission. Deterioration was defined that GA after discharge increased by ≥0.6% compared to the previous GA. Thirteen patients without deterioration up to 10 weeks after discharge were used as controls. In 8 patients with deterioration within 10 weeks after discharge, their HbA1c and GA at the time of admission and the decrease in HbA1c and GA during hospitalization were not significantly different from the control patients. At the time of deterioration, GA in the patients with deterioration increased significantly from 18.7 ± 2.7% to 21.0 ± 2.5%, whereas HbA1c decreased significantly from 9.1 ± 0.7% to 8.3 ± 0.6%. Subsequently, HbA1c increased significantly to 9.0 ± 0.8% together with GA. Thus, GA is useful for early detection of deterioration of glycemic control state after discharge from educational admission.