Corrected Sodium

Glucose is an effective osmole. When serum glucose rises, it increases extracellular tonicity, creating an osmotic gradient that draws water from the intracellular to the extracellular space. This influx of water dilutes the serum sodium concentration.

Corrected Na = Measured Na + [1.6 × (Glucose - 100) / 100]

The corrected sodium provides a better correlate for the patient’s mental status. If a patient is comatose with a measured sodium of 128 but a corrected sodium of 142, the altered mental status is likely due to hyperosmolarity or acidosis rather than hyponatremic encephalopathy.

A nephrologist and professor of medicine whose 1973 letter to the NEJM remains one of the most cited clinical rules in electrolyte management. His work simplified the bedside approach to "pseudohyponatremia" (a term now largely replaced by translational hyponatremia in this context).