Methods for identifying individuals who are not yet diabetic (pre-diabetic), but who are at significant risk of developing diabetes, such as type 2 diabetes, are disclosed herein. Methods are also provided for the identification of diabetic subjects. Also disclosed are methods for identifying individuals with diabetic complications. The methods include the identification of an overall glycosylation profile of proteins in a biological fluid, such as saliva, urine, or serum. In some examples, the methods include determining the amount of one or more protein in a biological fluid or determining the glycosylation pattern of one or more proteins in a biological fluid.