Hyperglycemia osmotically draws water into the vascular space, decreasing serum sodium concentration. In 1973, Katz1 theorized that sodium concentration should decrease by 1.6 mmol/L for every 100-mg/dL increase in serum glucose concentration (to convert serum glucose to millimoles per liter, multiply by 0.0555). More recent calculations suggest coefficients ranging from 1.35 to 2.0.2,3 A study in adults found empirical values ranging from 2.4 to 4.0,4 contrasting with theoretical estimates. We empirically determined the sodium correction factor for hyperglycemia using data from children with diabetic ketoacidosis.
Oh G, Anderson S, Tancredi D, Kuppermann N, Glaser N. Hyponatremia in Pediatric Diabetic Ketoacidosis: Reevaluating the Correction Factor for Hyperglycemia. Arch Pediatr Adolesc Med. 2009;163(8):771-772. doi:10.1001/archpediatrics.2009.106