If serum glucose is elevated, which other lab value may be falsely decreased?

When serum glucose levels are elevated, it can lead to a phenomenon known as pseudohyponatremia, wherein the measured serum sodium concentration appears lower than it actually is due to the dilution effect that high glucose levels have on the serum. Hyperglycemia causes water to move out of cells and into the serum, thus diluting other components, such as sodium, in the blood.

This connection between increased serum glucose and falsely decreased serum sodium is well-documented in clinical practice. When glucose rises significantly, especially in uncontrolled diabetes, this dilutional effect can substantially impact sodium readings, causing them to be misleadingly low.

While elevated serum glucose can also have implications for serum potassium and BUN levels, the primary laboratory value that is characteristically known to be falsely decreased due to hyperglycemia is serum sodium. Therefore, this makes serum sodium the primary answer to the question regarding which laboratory value may be falsely decreased when glucose levels are elevated.