Diabetes mellitus is a chronic metabolic disorder lasting for the lifetime of a person. Glucose and insulin are the main indicators in the monitoring and control of this disease. Most often, various laboratory tests are used in the diagnosis and control of diabetes. Among them, the estimation of blood glucose concentration is one of the main diagnostic criteria. Proper control of the blood glucose level can delay, and to a greater extent, prevent complications. Thus, blood glucose monitoring is a requisite tool in the management of diabetes mellitus. Insulin plays a major role in glucose metabolism and its determination is of great value in the diagnosis and control of diabetes. An uncountable number of biosensors have been developed based on various mechanisms which will make sure a continuous glucose as well as insulin monitoring. Biosensors became the most sophisticated tool for the detection of glucose and insulin and they are of different types. Enzymatic, non-enzymatic, electrochemical, optical, non-invasive, and continuous monitoring biosensors are discussed in this review. In recent years, there is progress towards the development of nanobiosensors using various nanomaterials. Here, we have reviewed the fabrication, modification, and recent approaches associated with insulin and glucose biosensors for the treatment of diabetes.