Application of Mass Spectrometry includes the ion and weights separation. The samples are usually introduced through a heated batch inlet, heated direct insertion probe, or a gas chromatograph. Ionization mass spectrometry (ESI-MS) which has become an increasingly important technique in the clinical laboratory for structural study or quantitative measurement of metabolites in a complex biological sample. Mass spectrometry is an analytical methods with high specificity and a growing presence in laboratory medicine. Various types of mass spectrometers are being used in an increasing number of clinical laboratories around the world, and, as a result, significant improvements in assay performance are occurring rapidly in areas such as toxicology, endocrinology, and biochemical markers. This review serves as a basic introduction to mass spectrometry, its uses, and associated challenges in the clinical laboratory and ends with a brief discussion of newer methods with the greatest potential for Clinical and Diagnostic Research.