Biochemical tests for pleural effusion include acidity and alkalinity, protein characterization and quantification, glucose volume, and lactate quantification. 1. pH: low pH with decreased glucose level indicates inflammatory effusion. 2. Protein characterization and quantification: oozing fluid has a high protein content and leaking fluid has a low protein content. 3. Glucose quantity: the blood glucose of the leaking fluid is the same as the normal human blood glucose, if the exudate needs to consume glucose due to bacterial reproduction, so the blood glucose of the exudate will be lower than the normal value. 4. Lactic acid quantification: The measurement of lactic acid content in pleural effusion helps in the diagnosis of bacterial and non-bacterial infections. When lactate reaches 6 mmol per liter or more, it suggests a bacterial infection. Pleural fluid biochemical tests also include lipid assay, adenosine deaminase, and amylase. When you need pleural effusion examination to find the cause of pleural effusion, you should go to the regular hospital in time to improve the biochemical examination of pleural effusion, and the interpretation of the examination report by professional doctors.