For every 100 mg/dL increase in glucose, how many mmol/L of sodium decrease?

For every 100 mg/dL increase in glucose, how many mmol/L of sodium decrease?

• A. 0.5
• B. 1.0
• C. 1.6
• D. 2.0

Answer: (C)

When glucose is elevated, its osmotic effect pulls water from cells into the extracellular space, diluting the sodium in the serum. For sodium, which carries a single positive charge, the typical correction factor used clinically is that the measured sodium decreases by about 1.6 mmol/L for every 100 mg/dL increase in glucose above normal. So the answer 1.6 reflects that standard adjustment. You can apply it as Na+ decrease ≈ 1.6 × (glucose rise in mg/dL / 100). For example, a 200 mg/dL rise would lower sodium by about 3.2 mmol/L. While some sources use other factors in specific situations, 1.6 is the commonly accepted value for this correction.

When glucose is elevated, its osmotic effect pulls water from cells into the extracellular space, diluting the sodium in the serum. For sodium, which carries a single positive charge, the typical correction factor used clinically is that the measured sodium decreases by about 1.6 mmol/L for every 100 mg/dL increase in glucose above normal. So the answer 1.6 reflects that standard adjustment. You can apply it as Na+ decrease ≈ 1.6 × (glucose rise in mg/dL / 100). For example, a 200 mg/dL rise would lower sodium by about 3.2 mmol/L. While some sources use other factors in specific situations, 1.6 is the commonly accepted value for this correction.