Definition

A CSF glucose test measures the amount of sugar (glucose) in the cerebrospinal fluid (CSF). CSF is a clear fluid that flows in the space surrounding the spinal cord and brain.

Alternative Names

Glucose test - CSF; Cerebrospinal fluid glucose test

How the Test is Performed

A sample of CSF is needed. A lumbar puncture, also called a spinal tap, is the most common way to collect this sample.

Other methods for collecting CSF are rarely used, but may be recommended in some cases. They include:

• Cisternal puncture
• Ventricular puncture
• Removal of CSF from a tube that is already in the CSF, such as a shunt or ventricular drain

The sample is sent to a laboratory for testing.

Why the Test is Performed

This test may be done to diagnose:

• Tumors
• Infections
• Inflammation of the central nervous system
• Delirium
• Other neurological and medical conditions

Normal Results

The glucose level in the CSF should be 50 to 80 mg/100 mL or 2.77 to 4.44 mmol/L (or greater than 2/3 of the blood sugar level).

Note: Normal value ranges may vary slightly among different laboratories. Talk to your health care provider about the meaning of your specific test results. Results can also be affected by your serum glucose level, especially if levels are extreme.

The examples above show the common measurements for results for these tests. Some laboratories use different measurements or may test different specimens.

What Abnormal Results Mean

Abnormal results include higher and lower glucose levels. Abnormal results may be due to:

• High blood sugar (hyperglycemia)
• Infection (bacterial or fungus)
• Inflammation of the central nervous system
• Tumor

References

Deluca GC, Griggs RC. Approach to the patient with neurologic disease. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 368.

Euerle BD. Spinal puncture and cerebrospinal fluid examination. In: Roberts JR, Custalow CB, Thomsen TW, eds. Roberts and Hedges' Clinical Procedures in Emergency Medicine and Acute Care. 7th ed. Philadelphia, PA: Elsevier; 2019:chap 60.

Rosenberg GA. Brain edema and disorders of cerebrospinal fluid circulation. In: Jankovic J, Mazziotta JC, Pomeroy SL, Newman NJ, eds. Bradley and Daroff's Neurology in Clinical Practice. 8th ed. Philadelphia, PA: Elsevier; 2022:chap 88.