The measure of glycated hemoglobin (HbA1c) concentration is the gold standard of glycemic control index in diabetes management and is well known as a marker for diabetes complications. However, HbA1c level neither accurately reflect glucose fluctuations, nor does it provide a clear indication of glycemic control in recent days or weeks. HbA1c concentration measurement can be confounded in patients with anemia, hemoglobinopathy, liver disease, or renal impairment. 1,5-Anhydroglucitol (1,5-AG) structurally resembles glucose. It can be influenced by diet or medication, gender and race, especially severe renal disease and various pathological conditions. Most notably, 1,5-AG level is reflective of short-term glucose status, postprandial hyperglycemia, and glycemic variability which are not captured by HbA1c assay. 1,5-AG may suggest an alternative index of subtypes of diabetes and a warning sign of diabetes complications. This review provides an overview of our current understanding of the role of 1,5-AG marker in diabetes. However, further investigations on the associations between this glycemic marker and diabetes complications are needed.