The normal value of glucose in the blood is 2.5-4.4 mmol/L. If the glucose in the cerebrospinal fluid is less than 2.25 mmol/L, this indicates a decrease in sugar. If the sugar is markedly reduced, it is seen in purulent meningitis. A mild to moderate decrease is seen in tuberculous meningitis or fungal meningitis, especially cryptococcal meningitis. Also, cerebrospinal fluid sugar reduction may occur with meningeal carcinomatosis. Increased sugar levels in cerebrospinal fluid are seen clinically in diabetic patients, and glucose in cerebrospinal fluid may be normal or slightly increased in viral encephalitis. The amount of sugar in the cerebrospinal fluid also depends on the patient’s blood glucose level, with glucose in the cerebrospinal fluid being about 50-70% of blood glucose.