Metabolic disease is defined as a disease due to abnormal biochemistry, usually as a result of an absent or deficient enzyme. Metabolic diseases also are known as inborn errors of metabolism. This is indeed a vast topic from Practice of Medicine and important because metabolism forms the very basis of sustenance of life. There are a huge number of metabolic processes in human body running simultaneously in order to maintain the body in a state of health. But equally large is the number of metabolic diseases which come up as a consequence of a fault in any of these metabolic processes.

The subject of Metabolic Diseases is vast and complex. Attempt has been made to cover metabolic diseases in a systematic and simplified manner. The disorders have been classified into disorders of homeostasis, acid base imbalance, metabolism of biomolecules and porphyrias. A detailed module on Diabetes Mellitus has been added with an aim to cover this disorder of carbohydrate metabolism in depth because it is also a lifestyle disorder and an extremely common ailment in today’s medical practice.