CSF glucose test
Glucose test - CSF; Cerebrospinal fluid glucose test
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.
A lumbar puncture, or spinal tap, is a procedure to collect cerebrospinal fluid to check for the presence of disease or injury. A spinal needle is inserted, usually between the third and fourth lumbar vertebrae in the lower spine. Once the needle is properly positioned in the subarachnoid space (the space between the spinal cord and its covering, the meninges), pressures can be measured and fluid can be collected for testing.
How the Test is Performed
A sample of CSF is needed [1 to 5 milliliters (ml)]. A lumbar puncture (spinal tap), is the most common way to collect this sample. Rarely, other methods are used for collecting CSF such as:
- Cisternal puncture
- Ventricular puncture
- Removal of CSF from a tube that is already in the CSF, such as a shunt or ventricular drain
After the sample is taken, it is sent to a lab for evaluation.
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).
Normal value ranges may vary slightly among different labs. 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 labs 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
De Luca GC, Griggs RC, Johnston SC. Approach to the patient with neurologic disease. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 366.
Karcher DS, McPherson RA. Cerebrospinal, synovial, serous body fluids, and alternative specimens. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Philadelphia, PA: Elsevier; 2022:chap 30.
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.
Schnapp BH, Jewell C. Central nervous system infections. In: Walls RM, ed. Rosen's Emergency Medicine: Concepts and Clinical Practice. 10th ed. Philadelphia, PA: Elsevier; 2023:chap 95.
Version Info
Last reviewed on: 4/16/2025
Reviewed by: Joseph V. Campellone, MD, Department of Neurology, Cooper Medical School at Rowan University, Camden, NJ. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
