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Cerebrospinal Fluid

CSF is normally sterile, colorless, and clear. It contains most of the same constituents as blood, but generally in lower concentrations.

CSF clarity

Holding the test tube of CSF against a white, printed page, the CSF should be as clear as a similar test tube filled with water.

  • Yellow (+1 to +4) color indicates possible:
    • Previous subarachnoid bleeding
    • Severe jaundice
    • Large amounts of protein (>150 mg/dL)
  • Bloody or blood-tinged indicates possible:
    • Bloody tap
    • Subarachnoid or cerebral hemorrhage
    • At least 400 RBC/µL must be present before the CSF is visibly bloody
  • Turbid CSF usually indicates the presence of:
    • WBC,
    • RBCs
    • Bacteria, or
    • Other microorganisms

Spinal fluid glucose

Spinal fluid glucose is decreased in many cases of:

  • Bacterial meningitis
  • Mumps meningitis
  • Meningococcal meningitis
  • Tuberculosis meningitis
  • Herpes meningitis
  • Neurosyphilis
  • Sarcoidosis
  • Cancer
  • Subarachnoid hemorrhage

Spinal fluid glucose may be elevated:

  • 24 hours after hyperglycemia

White blood cell count

Normal CSF has very few WBCs (08/mm3). In the presence of an inflammatory response, WBCs increase. Inflammatory response situations include:

  • Meningitis of all types
  • Cerebral abscess
  • CNS hemorrhage
  • Foreign body reaction
  • CNS metastatic tumors
  • CNS infarction

A predominence of monocytes (rather than neutrophils) suggests a non-bacterial source of inflammation, such as:

  • Hemorrhage
  • Viral infection
  • Syphilis
  • Tuberculosis
  • Multiples

Red blood cell count

Normally, there are no RBCs or nearly none (<1 RBC/mm3). While a traumatic lumbar puncture ("bloody tap") can result in RBCs being present in the CSF, the blood will progressively clear with each tube of CSF withdrawn. By the third tube, the CSF should be nearly clear, even with a bloody tap.

Blood that is evenly distributed throughout the three tubes reflects CNS bleeding, such as:

  • Subarachnoid hemorrhage
  • Cerebral hemorrhage
  • Spinal cord bleeding

CSF culture

CSF is normally sterile.

In the presence of bacterial meningitis:

  • CSF is cloudy (purulent)
  • CSF glucose is decreased in half the cases
  • WBCs are increased
  • WBCs are primarily PMNs

In the presence of non-bacterial meningitis (viral, tubercular, fungal, protozoal, etc.):

  • CSF is clear
  • CSF glucose is normal or decreased
  • WBC monocyte count is decreased

Normal Values*

CSF clarity Clear  
CSF glucose  60–70% of blood glucose  
CSF glucose (adult) 4070 mg/dL 2.23.9 mmol/L
CSF glucose (child) 6080 mg/dL 3.34.4 mmol/L
CSF WBC count 08 leukocytes/mm3  
CSF RBC count <1 RBC/mm3  
CSF protein 1545 mg/dL 150450 mg/L
CSF culture Sterile  

*These are general values taken from a variety of sources. The actual normal values may vary from lab to lab and from one type of testing protocol to another.

Source: Operational Medicine 2001, Health Care in Military Settings, NAVMED P-5139, May 1, 2001, Bureau of Medicine and Surgery, Department of the Navy, 2300 E Street NW, Washington DC, 20372-5300, USA