Medical Laboratory Scientist (MLS) ASCP Practice Exam 2025 – Your Comprehensive All-in-One Guide to Exam Success!

The ranking of glucose levels among whole blood, serum, and cerebrospinal fluid (CSF) is significant because it reflects the physiology of glucose metabolism and transport in the body.

Serum glucose levels are typically higher than whole blood glucose levels. This is primarily because whole blood includes both the plasma and the cellular components (red blood cells, white blood cells, and platelets), and glucose is present in the plasma portion. When whole blood is separated into its components, the serum (which is the liquid part of blood after clotting and does not include cells) contains a higher concentration of glucose due to the absence of red blood cells which utilize some glucose for metabolism.

In comparison, CSF glucose levels are normally lower than both serum and whole blood. The glucose concentration in CSF is generally about two-thirds that of serum. This lower concentration is due to the selective permeability of the blood-brain barrier and the utilization of glucose by cells within the central nervous system. Therefore, the hierarchy of glucose concentrations in whole blood, serum, and CSF is accurately represented by ranking serum as having the highest levels, followed by whole blood, and then CSF with the lowest.

This physiological understanding substantiates the rankings, thus confirming that the order is