Which of the following CSF glucose ranges is considered normal?

Which of the following CSF glucose ranges is considered normal?

• A. 60-90 mg/dL
• B. 70-100 mg/dL
• C. 50-80 mg/dL
• D. 40-60 mg/dL

Answer: (C)

CSF glucose comes from the blood and moves into the CSF, so its level tracks serum glucose rather than being produced in the CSF. In a healthy state, CSF glucose is about two-thirds of the plasma glucose, which places the normal CSF glucose range roughly in the 50–80 mg/dL area. That’s why the range around 50–80 mg/dL is considered normal—it accommodates the typical variation you’d see with normal plasma glucose levels and translation into CSF. Values significantly below this range can indicate infection or inflammation (hypoglycorrhachia), while much higher values are less consistent with normal physiology. The other options fall outside the common normal window or align more with pathological states.

CSF glucose comes from the blood and moves into the CSF, so its level tracks serum glucose rather than being produced in the CSF. In a healthy state, CSF glucose is about two-thirds of the plasma glucose, which places the normal CSF glucose range roughly in the 50–80 mg/dL area. That’s why the range around 50–80 mg/dL is considered normal—it accommodates the typical variation you’d see with normal plasma glucose levels and translation into CSF. Values significantly below this range can indicate infection or inflammation (hypoglycorrhachia), while much higher values are less consistent with normal physiology. The other options fall outside the common normal window or align more with pathological states.