From the Research
For a glucose level of 266 mg/dL, the expected degree of factitious hyponatremia would be approximately 2.4 mEq/L, as the most recent and highest quality study suggests a correction factor of 2.4 meq/L decrease in serum sodium concentration for every 100 mg/dL increase in glucose concentration 1. This means that the measured serum sodium concentration would be about 2.4 mEq/L lower than the true sodium concentration. To correct for this effect, you can use the formula that for every 100 mg/dL increase in glucose above normal (approximately 100 mg/dL), serum sodium decreases by 2.4 mEq/L. In this case, with glucose at 266 mg/dL, there is an increase of 166 mg/dL above normal, resulting in the calculated sodium depression. This phenomenon occurs because hyperglycemia creates an osmotic gradient that draws water from the intracellular to the extracellular space, diluting the sodium concentration in the serum without changing the total body sodium content. When treating patients with hyperglycemia and hyponatremia, it's essential to calculate this corrected sodium value to avoid misdiagnosis of the severity of hyponatremia and to guide appropriate fluid management, as supported by a study that found corrected sodium levels to be a better predictor of clinical outcomes than measured sodium levels in patients with extreme hyperglycemia 2. Key points to consider include:
- The correction factor for hyperglycemia-induced hyponatremia is 2.4 meq/L decrease in serum sodium concentration for every 100 mg/dL increase in glucose concentration 1
- The corrected sodium level is a better indicator of clinical outcomes compared to measured sodium levels in patients with severe hyperglycemia 2
- Hyperglycemia creates an osmotic gradient that draws water from the intracellular to the extracellular space, diluting the sodium concentration in the serum without changing the total body sodium content 3