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. 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) ...