Health & Fitness
Corrected Sodium for Hyperglycemia (DKA / HHS): Katz & Hillier Formulas
Correct dilutional hyponatremia in Diabetic Ketoacidosis (DKA) and Hyperosmolar Hyperglycemic State (HHS) using Katz's +1.6 mEq/L and Hillier's +2.4 mEq/L per 100 mg/dL serum glucose above 100.
Unmask true hypernatremic dehydration hidden behind high blood sugar!
In Diabetic Ketoacidosis (DKA) and HHS, severe extracellular hyperglycemia acts as an osmotic magnet—pulling intracellular water out of cells into plasma and diluting measured serum sodium! A patient presenting with measured Na+ = 128 mEq/L and Glucose = 600 mg/dL is NOT truly hyponatremic—administering hypotonic fluids too rapidly risks cerebral edema!
Two landmark osmotic-shift formulas adjust measured Na+ for every 100 mg/dL of glucose above normal 100 mg/dL (using MAX(0, Glucose - 100) so normal/low glucose <= 100 is never downward-adjusted!): 1) Katz (NEJM, 1973) Classic Rule: Na_Katz = Na_measured + (1.6 * (MAX(0, Glucose - 100) / 100)) (128 + 8.0 = 136.0 mEq/L); and 2) Hillier et al. (Am J Med, 1999) Experimental Rule (preferred when Glucose > 400 mg/dL): Na_Hillier = Na_measured + (2.4 * (MAX(0, Glucose - 100) / 100)) (128 + 12.0 = 140.0 mEq/L)!
| Correction Method (Measured Na = 128 mEq/L) | Glucose = 600 mg/dL (+500 excess) | Glucose = 90 mg/dL (Euglycemic) | Clinical Selection |
|---|---|---|---|
| Katz (1973) +1.6 Factor | 128 + 1.6 * 5 = 136.0 mEq/L | 128.0 mEq/L (Unchanged) | Standard <= 400 mg/dL |
| Hillier (1999) +2.4 Factor | 128 + 2.4 * 5 = 140.0 mEq/L | 128.0 mEq/L (Unchanged) | Preferred in severe DKA/HHS > 400 |
| Auto-Switched ADA Hybrid | IF(Gluc > 400, Hillier, Katz) | 140.0 mEq/L at 600 | Applies 1.6 <=400, 2.4 >400 |
Katz Hyperglycemia-Corrected Serum Sodium (+1.6 per 100 mg/dL > 100)
Adds 0.016 * MAX(0, Glucose_mg_dL - 100) to measured serum sodium B2 (mEq/L).
=IF(OR(B2 <= 0, B3 <= 0), "Invalid Lab Input", ROUND(B2 + (1.6 * (MAX(0, B3 - 100) / 100)), 1))Hillier Severe-Hyperglycemia Sodium Correction (+2.4 per 100 mg/dL > 100)
Captures steeper osmotic water shift observed when serum glucose exceeds 400 mg/dL.
=ROUND(B2 + (2.4 * (MAX(0, B3 - 100) / 100)), 1)Try the example
Use the original values or change them to test your understanding.