Glucose, Cerebrospinal Fluid (CSF)

Glucose in the CSF is about two thirds of the serum glucose measured during the preceding 2 " “4 hours in normal adults. This ratio decreases with increasing serum glucose levels. CSF glucose levels generally do not go above 300 mg/dL regardless of serum levels. Critical values are <30 mg/dL. Glucose in the CSF of neonates varies much more than that in adults, and the CSF-to-serum ratio is generally higher than in adults.

Normal range: 50 " “80 mg/dL.

Use

Diagnosis of tumors, infections, inflammation of the CNS, and other neurologic and medical conditions.

Interpretation

Increased In

Elevated levels of glucose in the blood

CNS syphilis

Decreased In

CNS infections (glucose levels are usually normal in viral infections)

Chemical meningitis

TB meningitis

Cryptococcal meningitis

Mumps

Primary and metastatic tumors of meninges

Sarcoidosis

Inflammatory conditions

Subarachnoid hemorrhage

Hypoglycemia

Limitations

Normal glucose levels do not rule out infection because up to 50% of patients who have bacterial meningitis have normal CSF glucose levels.