This textbook introduces the clinical applications of biomolecules in disease diagnosis, covering a range of topics in biochemistry. The book discusses carbohydrate and protein metabolism abnormalities, lipid digestion and absorption defects, disorders of purine and pyrimidine metabolism, and the chemistry and biological roles of water- and fat-soluble vitamins. It also covers the roles of different macroelements and essential trace elements in physiological processes and the prevention of chronic diseases. The final chapter focuses on recent developments in our understanding of the role of enzymes in disease development and diagnosis. The book chapter also explores the causes and effects of free radicals in the body, including oxidative stress and diseases such as cardiovascular and neurodegenerative diseases. Finally, the chapter discusses cancer development, causes, diagnosis methods, biomarkers, and current treatments such as targeted drug therapy, chemotherapy, and radiation therapy. This book is a useful resource for undergraduate and postgraduate students, researchers and practitioners in biochemistry, medicine, and health sciences.