Diabetes mellitus (DM) is a chronic metabolic disease characterized by hyperglycemia that occurs as a result of impaired insulin secretion and/or insulin effect, or both of these factors. The fact that the disease has both individual and social dimensions makes it important to detect as early as possible and make the necessary lifestyle changes. For this purpose, it becomes necessary to develop fast, effortless, cheap, and reliable methods for diagnosis. We discussed which biochemical markers should enter routine use according to their sensitivity and specificity among the biochemical markers that have been used and are still being studied. In this chapter, we explored some methods that may be used as biomarkers and discussed advantages and pitfalls for each.