Medical diagnostics plays a significant role in clinical decisions. The first medical laboratory test to be developed was urine analysis, in which urine properties were analyzed for diagnosis. Urine analysis has been long used as a routine laboratory test that was improved with the development of sampling and test methods. As the field of hematology progressed with the invention of the microscope, blood tests were developed. Demands for tests based on clinical chemistry have existed since the 17th century, and research using patient blood began in the 18th century. In the 20th century, with the development of the spectrophotometer, chemical analyses were performed for diagnostic purposes. With the appearance of cholera outbreaks, the identification of microorganisms was necessary for patient diagnosis, and the development of specific test methods contributed to microorganism detection in the laboratory. Blood transfusion, which started with blood collection in the 15th century, is currently used as a therapeutic method in medicine. Moreover, once the hypothesis of acquired immunity was proven in the 18th century, various methods for measuring immunity were developed. Molecular diagnosis, which was established during the 20th century after the presentation of Mendel's Genetic Laws in the 19th century, developed rapidly and became the predominant field in medical laboratory diagnostics. Thus, medical laboratory technology became an academic field, with foundations based on basic sciences. Modern medicine will further progress thanks to medical advancements, leading to an extension of average human lifespan up to 100 years. Laboratory medicine will provide significant support for this development.