This book provides an exploration of clinical biochemistry, serving as both a foundational text and a guide to its modern applications in medicine. It begins with an introduction to clinical biochemistry, highlighting its evolution as a discipline that connects the core principles of biochemistry with the practical requirements of medical diagnostics. The fundamentals of clinical biochemistry are presented in a way that builds a clear conceptual framework, covering the essential biochemical processes and their relevance to health and disease. This section provides readers with the necessary background in metabolism, molecular interactions, and biochemical regulation, equipping them with the knowledge to appreciate the more advanced diagnostic techniques explored in later chapters. Following this, the book delves into the organization of clinical laboratories and the importance of quality control. Emphasis is placed on accuracy, reliability, and standardization, underscoring how rigorous laboratory practices are indispensable for producing trustworthy diagnostic results. The discussion of analytical techniques in clinical biochemistry introduces readers to the diverse tools and methods that underpin diagnostic testing. From spectrophotometry to chromatography and electrophoresis, the text explains how these analytical approaches are used to measure and analyze biochemical substances in clinical samples. Building upon these traditional methods, the book also addresses molecular diagnostic techniques, reflecting the rapid advancements in technology that have transformed clinical practice. Topics such as polymerase chain reaction, sequencing, and microarray analysis are presented as vital innovations that expand diagnostic capabilities and enable the detection of genetic and molecular markers of disease. The clinical applications of biochemistry form the core of the book, where theory and technique are connected to practical medicine. Blood chemistry is explored as a central diagnostic field, offering insights into the measurement of glucose, lipids, electrolytes, and metabolites that provide critical information about patient health. Hormones and endocrinology are discussed in relation to their biochemical basis and diagnostic evaluation, emphasizing how hormonal assays aid in identifying disorders of the thyroid, adrenal glands, and other endocrine systems. The section on enzymology highlights the diagnostic significance of enzymes as markers of tissue damage and disease progression, particularly in conditions affecting the liver, heart, and muscles. Proteins and immunochemistry are also examined, showcasing how the measurement of plasma proteins, immunoglobulins, and antigen-antibody interactions play an important role in the diagnosis and monitoring of immune-related and systemic diseases.