Clinical Laboratory Science Practice Test 2026: All-in-One Guide to Master Urinalysis and Body Fluids

Glucose gets from the blood into the CSF by diffusion across the blood-brain barrier, so the CSF glucose concentration tracks serum glucose but stays lower. In the normal state, CSF glucose is about 60% of serum glucose. So if serum glucose is around 100 mg/dL, CSF glucose is typically about 60 mg/dL. This ratio helps clinicians: a markedly lower CSF glucose relative to serum can indicate conditions like meningitis, whereas a normal or higher CSF glucose is less concerning.