This review discusses the field of biosensors, highlighting their importance in various applications such as medicine, food, environmental monitoring, and security. The biosensors industry is now worth billions of dollars, with a significant portion of the market driven by medical diagnostics, particularly glucose sensors for diabetes patients. The review outlines the two main categories of biosensors: sophisticated, high-throughput laboratory machines and easy-to-use, portable devices for non-specialists. Electrochemical biosensors dominate the field, while bioaffinity monitoring is primarily done using optical techniques. Emerging technologies such as semi-synthetic and synthetic receptors, along with nanomaterials, are improving the sensitivity and versatility of biosensors. The review also discusses the development of biosensors for diabetes, highlighting the success of mediated amperometric glucose sensors. These sensors have been developed by various companies, including MediSense and Abbott, and have become a major part of the market. The review also covers the development of implantable biosensors and non-invasive monitoring techniques, which are still in early stages of development. The review emphasizes the importance of biosensors in healthcare, particularly in the context of diabetes management and the potential for future advancements in biosensor technology. The review concludes by discussing emerging technologies such as molecularly imprinted polymers and electropolymerisation, which are showing promise in the development of more sensitive and specific biosensors.This review discusses the field of biosensors, highlighting their importance in various applications such as medicine, food, environmental monitoring, and security. The biosensors industry is now worth billions of dollars, with a significant portion of the market driven by medical diagnostics, particularly glucose sensors for diabetes patients. The review outlines the two main categories of biosensors: sophisticated, high-throughput laboratory machines and easy-to-use, portable devices for non-specialists. Electrochemical biosensors dominate the field, while bioaffinity monitoring is primarily done using optical techniques. Emerging technologies such as semi-synthetic and synthetic receptors, along with nanomaterials, are improving the sensitivity and versatility of biosensors. The review also discusses the development of biosensors for diabetes, highlighting the success of mediated amperometric glucose sensors. These sensors have been developed by various companies, including MediSense and Abbott, and have become a major part of the market. The review also covers the development of implantable biosensors and non-invasive monitoring techniques, which are still in early stages of development. The review emphasizes the importance of biosensors in healthcare, particularly in the context of diabetes management and the potential for future advancements in biosensor technology. The review concludes by discussing emerging technologies such as molecularly imprinted polymers and electropolymerisation, which are showing promise in the development of more sensitive and specific biosensors.