Nonenzymatic glycosylation refers to the chemical process whereby glucose attaches to proteins without the aid of enzymes. The degree of glycosylation is proportionate to the level of blood glucose. Many proteins, including hemoglobin, undergo nonenzymatic glycosylation. Because RBCs have a life span of about 120 days, the amount of glycosylated hemoglobin is a function of the blood glucose level over the previous 120-day period. The level of glycosylated hemoglobin is not appreciably affected by short-term changes in plasma glucose levels. Random glucose testing is an immediate way of monitoring short-term adjustments with diet and medications such as insulin and oral agents. Fasting glucose testing affords a better way to diagnose diabetes mellitus initially. Measurements of cholesterol and fructosamine have no value in managing diabetes mellitus. Microalbuminuria may presage the development of the diabetic renal disease. The "incretin effect" is diminished in patients with type 2 diabetes, and the use of GLP-1 receptor agonists can help to restore incretin function and lead to improved glycemic control and loss of weight via increased satiety.