Cerebrospinal fluid glucose is typically approximately what percentage of plasma glucose?

Cerebrospinal fluid glucose is typically approximately what percentage of plasma glucose?

• A. 30%
• B. 60%
• C. 90%
• D. 120%

Answer: (B)

CSF glucose reflects plasma glucose because glucose crosses into the CSF by facilitated diffusion across the blood-brain barrier, mainly via GLUT1 transporters, and brain tissue consumes some of the glucose as well. In healthy individuals, the CSF glucose level is typically about 60% of the plasma level. For example, if plasma glucose is 5.0 mmol/L, CSF glucose is usually around 3.0 mmol/L. The ~60% relationship arises from diffusion-limited transport and ongoing cerebral utilization. Values around 30% would imply unusually low transport or high consumption, while 90% or more would not align with how glucose moves into CSF.

CSF glucose reflects plasma glucose because glucose crosses into the CSF by facilitated diffusion across the blood-brain barrier, mainly via GLUT1 transporters, and brain tissue consumes some of the glucose as well. In healthy individuals, the CSF glucose level is typically about 60% of the plasma level. For example, if plasma glucose is 5.0 mmol/L, CSF glucose is usually around 3.0 mmol/L. The ~60% relationship arises from diffusion-limited transport and ongoing cerebral utilization. Values around 30% would imply unusually low transport or high consumption, while 90% or more would not align with how glucose moves into CSF.