Looking for more details? Read our comprehensive Corrected Sodium guide
Why Calculate Corrected Sodium?
Hyperglycemia increases the osmolarity of the extracellular fluid (ECF). This causes water to shift from the intracellular space to the extracellular space, diluting the serum sodium concentration and leading to a factitious hyponatremia. Calculating the corrected sodium helps determine if there is an underlying true sodium derangement.
Formula (Katz)
Note: This is the traditional Katz formula, which adds 1.6 mEq/L to the sodium for every 100 mg/dL increase in glucose above 100 mg/dL.
Interpretation
- Corrected Na⁺ < 135: True Hyponatremia. Reflects a relative excess of water.
- Corrected Na⁺ 135-145: Normal Sodium balance. The measured hyponatremia is entirely factitious due to hyperglycemia.
- Corrected Na⁺ > 145: True Hypernatremia. Indicates a significant free water deficit, commonly seen in HHS or DKA.
How to Use
Enter the measured serum sodium and the serum glucose level. The tool applies the correction factor (commonly 1.6 or 2.4 mEq/L for every 100 mg/dL glucose over 100) to find the true sodium.
Case Example
Patient: Patient with DKA. Na: 130 mEq/L, Glucose: 600 mg/dL.
Calculation: Using Katz formula: Corrected Na = 130 + 1.6 * ((600 - 100) / 100) = 138 mEq/L.
Interpretation: The corrected sodium is normal (138 mEq/L), indicating that the hyponatremia is dilutional due to hyperglycemia.
Frequently Asked Questions
The traditional Katz formula uses 1.6 mEq/L. However, studies (e.g., Hillier et al.) suggest a factor of 2.4 is more accurate when glucose exceeds 400 mg/dL.
High blood glucose acts as an osmole, pulling water from the intracellular space into the extracellular space, which dilutes the serum sodium concentration.