Results for electrolytes, sodium is low. All other electrolytes are normal. What to do?

Results for electrolytes, sodium is low. All other electrolytes are normal. What to do?

• A. Check for specimen glucose
• B. Measure sodium using indirect ISE
• C. Examine for hemolysis
• D. Report the result

Answer: (A)

When sodium appears low but other electrolytes are normal, consider a dilutional artifact caused by high glucose. Hyperglycemia raises plasma osmolality and pulls water into the extracellular space, diluting sodium and making it look deceptively low. The best immediate step is to measure the specimen glucose to see if it’s elevated; if glucose is high, the hyponatremia may be spuriously low due to this effect. If needed, you can apply a corrected sodium calculation (about 1.6 mEq/L added to the measured sodium for every 100 mg/dL of glucose above 100 mg/dL) and reassess. If glucose isn’t elevated, explore other causes, but the glucose check is the most appropriate first move. Hemolysis could affect other analytes more and wouldn’t explain isolated low sodium, and reporting without investigating the cause wouldn’t resolve the discrepancy.

When sodium appears low but other electrolytes are normal, consider a dilutional artifact caused by high glucose. Hyperglycemia raises plasma osmolality and pulls water into the extracellular space, diluting sodium and making it look deceptively low. The best immediate step is to measure the specimen glucose to see if it’s elevated; if glucose is high, the hyponatremia may be spuriously low due to this effect. If needed, you can apply a corrected sodium calculation (about 1.6 mEq/L added to the measured sodium for every 100 mg/dL of glucose above 100 mg/dL) and reassess. If glucose isn’t elevated, explore other causes, but the glucose check is the most appropriate first move. Hemolysis could affect other analytes more and wouldn’t explain isolated low sodium, and reporting without investigating the cause wouldn’t resolve the discrepancy.