II. Physiology: Sodium homeostasis
III. Interpretation: General
- Normal: 135-145 mEq/L
- Abnormal
- Hypernatremia
- Serum Sodium over 145
- Hyponatremia
- Serum Sodium under 135
- Hypernatremia
IV. Interpretation: Corrected Serum Sodium for Glucose
-
Glucose draws water into the intravascular space via osmotic pressure, and dilutes Serum Sodium
- Measured Serum Sodium in hyperglycermia is a true Hyponatremia
- However the Serum Sodium corrects with normalization of Glucose
- Katz Formula
- Adjust measured Serum Sodium (sNa) upwards by 1.6 meq/L per 100 mg/dl increase in plasma Glucose
- Corrected Serum Sodium = sNa + 0.016 * (Serum Glucose - 100)
- Katz (1973) N Engl J Med 289(16): 843-4 [PubMed]
- Hillier Formula
- Alternative equation suggests correction should be 2.4 meq/L per 100 mg/dl increase in plasma Glucose
- Corrected Serum Sodium = sNa + 0.024 * (Serum Glucose - 100)
- Although Hillier equation is thought more accurate, Katz equation is used most commonly
- Hillier (1999) Am J Med 106(4): 399-403 [PubMed]
V. Resources
- MDCalc Corrected Serum Sodium