Adjust sodium for hyperglycemia.
Hyperglycemia causes dilutional hyponatremia. Katz formula: add 1.6 mEq/L Na per 100 mg/dL glucose above 100. Hillier formula: add 2.4 mEq/L (more accurate at glucose > 400). If corrected Na is high, the patient is actually hypernatremic despite low measured Na.