This chapter discusses the commonly performed tests for the interpretation of abnormalities of the parameters involved in various diseases. It gives brief overviews of various tests required to detect the abnormalities related to different diseases, including liver function tests, renal function tests, cardiac markers, pulmonary function tests, arterial blood gas checkers, tests for electrolyte disorders, serum protein electrophoresis, urinalysis, cerebrospinal fluid, coagulogram and complete hemogram. The chapter also provided charts showing the reference ranges of different parameters associated with different tests that are done on patients to reach correct diagnosis of a disease. Tests such as Forced vital capacity (FVC) is a measure of lung volume and is usually reduced in diseases that cause the lungs to be smaller which are termed as restrictive disorders of the lung parenchyma, such as pulmonary fibrosis, or of the bellows, including kypho scoliosis, neuromuscular disease, and pleural effusion. Urinalysis reveals diseases that have gone unnoticed as they do not produce striking signs or symptoms. These diseases include diabetes mellitus, various forms of glomerulonephritis, and chronic urinary tract infections.