Visibly hemolyzed samples may give misleading results.
Bloody taps cause falsely increased glucose, since there is more glucose in blood.
Low CSF glucose may also occur in subarachnoid hemorrhage and neoplasia, uncommonly in herpes or mumps meningoencephalitis, including CNS leukemia. It has led to the diagnosis of insulinoma pesenting with CNS symptoms. Sarcoidosis and neurosyphilis are also reported causes of low CSF glucose. Lactic acid may be useful in the diagnosis of bacterial meningitis.