Cloudy cerebrospinal fluid represents an increase in the clarity of the cerebrospinal fluid. Among the laboratory tests of cerebrospinal fluid, transparency is one of the items in the cerebrospinal fluid routine, which is usually expressed as clear, slightly mixed, or cloudy. Normal cerebrospinal fluid is colorless and clear, while cloudy is abnormal and slightly cloudy is also abnormal. When the cerebrospinal fluid is cloudy, it is usually seen in diseases of the central nervous system such as hemorrhage, inflammation, or tumors. A large increase in the number of cells or bacteria in the cerebrospinal fluid leads to an increase in clarity, which can appear as either slightly mixed or cloudy, such as in septic meningitis, where the number of cells increases significantly and the appearance of the cerebrospinal fluid becomes cloudy. In tuberculous meningitis, there is a moderate increase in the number of cells and the appearance may appear cloudy in a gross glass-like manner. In viral meningitis, the increase in cell count is not significant and the appearance can be clear or slightly cloudy.