Corrected Sodium Calculation in Diabetic Ketoacidosis
The Formula
The corrected sodium is calculated by adding 1.6 mEq/L to the measured sodium for every 100 mg/dL of glucose above 100 mg/dL. 1, 2
The formula is: Corrected [Na+] = Measured [Na+] + 1.6 × ([Glucose in mg/dL - 100]/100) 2
This correction accounts for the dilutional effect of hyperglycemia on measured sodium, as glucose draws water from the intracellular to the extracellular space, artificially lowering the measured sodium concentration. 3
Clinical Examples
Example 1: Typical DKA with Normal Measured Sodium
- Measured sodium: 135 mEq/L
- Glucose: 600 mg/dL
- Calculation: 135 + 1.6 × [(600 - 100)/100] = 135 + 1.6 × 5 = 135 + 8 = 143 mEq/L
- Interpretation: Normal corrected sodium → use 0.45% NaCl at 4-14 ml/kg/h after initial resuscitation 1, 2
Example 2: DKA with Low Measured Sodium
- Measured sodium: 128 mEq/L
- Glucose: 800 mg/dL
- Calculation: 128 + 1.6 × [(800 - 100)/100] = 128 + 1.6 × 7 = 128 + 11.2 = 139.2 mEq/L
- Interpretation: Low-normal corrected sodium → continue 0.9% NaCl at 4-14 ml/kg/h after initial resuscitation 1, 2
Example 3: HHS with Severe Hyperglycemia
- Measured sodium: 145 mEq/L
- Glucose: 900 mg/dL
- Calculation: 145 + 1.6 × [(900 - 100)/100] = 145 + 1.6 × 8 = 145 + 12.8 = 157.8 mEq/L
- Interpretation: Elevated corrected sodium indicating significant free water deficit → use 0.45% NaCl at 4-14 ml/kg/h after initial resuscitation 2
Example 4: Extreme Hyperglycemia with Hypernatremia (from Case Report)
- Measured sodium: 144 mEq/L
- Glucose: 979 mg/dL
- Calculation: 144 + 1.6 × [(979 - 100)/100] = 144 + 1.6 × 8.79 = 144 + 14.1 = 158.1 mEq/L
- Interpretation: Severe hypernatremia requiring half-normal saline (0.45% NaCl) for correction 4
Example 5: Severe HHS (from Research Data)
- Measured sodium: 148 mEq/L
- Glucose: 1000 mg/dL
- Calculation: 148 + 1.6 × [(1000 - 100)/100] = 148 + 1.6 × 9 = 148 + 14.4 = 162.4 mEq/L
- Interpretation: Severe hypernatremia typical of HHS, where mean corrected sodium reaches 160.8 mEq/L 3
Critical Clinical Application
The corrected sodium—not the measured sodium—determines fluid choice after the initial hour of isotonic saline resuscitation. 1, 2
- If corrected sodium is low: Continue 0.9% NaCl at 4-14 ml/kg/h 1, 2
- If corrected sodium is normal or elevated: Switch to 0.45% NaCl at 4-14 ml/kg/h 1, 2
Important Caveats
Never use measured sodium alone to guide fluid therapy—this is a critical error that can lead to inappropriate fluid selection. 2, 5
The corrected sodium may change during treatment due to ongoing osmotic diuresis and fluid losses, requiring recalculation every 2-4 hours during active management. 2, 3
In patients with stage 5 chronic kidney disease and hyperglycemia, the mean corrected sodium is typically 139.0 mEq/L (eunatremic range), whereas in HHS with preserved renal function, it averages 160.8 mEq/L (severe hypernatremia range). 3
The rate of osmolality reduction must not exceed 3 mOsm/kg/h to prevent cerebral edema, which carries significant mortality risk, particularly in pediatric patients. 1, 2
Note that effective serum osmolality for monitoring treatment severity uses the measured (uncorrected) sodium: 2[measured Na] + glucose/18, not the corrected sodium. 2