Objective To explore the relationship between serum glucose critical value and the clinical practice. Methods The critical value detected in our clinical laboratory from January 2012 to January 2014 were recorded, and the serum glucose critical value characteristics and distribution rule were analyzed. Results 3349 cases of critical value were reported. The serum glucose accounted for 216 cases (6.45%). Among them, the critical value of hypoglycaemia was 71 cases (33%), and high blood sugar critical value was 145 cases (67%). The critical value cases were mainly found in the digestive system diseases and diabetes. Conclusion The limit scope of our serum sugar critical value is too narrow, and the critical value range could be set up scientifically based on the actual situation.