Corrected Sodium Calculation for Hyperglycemia
For a patient with sodium of 136 mEq/L and glucose of 253 mg/dL, the corrected sodium is approximately 140 mEq/L, calculated by adding 1.6 mEq/L for every 100 mg/dL glucose above 100 mg/dL.
Calculation Method
The standard correction formula accounts for the dilutional effect of hyperglycemia on measured sodium 1, 2:
- Measured sodium: 136 mEq/L
- Glucose elevation: 253 - 100 = 153 mg/dL above baseline
- Correction factor: Add 1.6 mEq/L for each 100 mg/dL glucose elevation 1
- Calculation: 136 + (153/100 × 1.6) = 136 + 2.4 = 138.4 mEq/L (approximately 138-140 mEq/L)
The American Diabetes Association guidelines specifically state: "Serum Na should be corrected for hyperglycemia (for each 100 mg/dl glucose >100 mg/dl, add 1.6 mEq to sodium value for corrected serum value)" 1.
Clinical Interpretation
This corrected sodium of approximately 140 mEq/L indicates eunatremia, meaning the patient does not have true hyponatremia despite the measured value of 136 mEq/L 2. The low measured sodium is artifactual, caused by the osmotic shift of water from the intracellular to extracellular space due to hyperglycemia 2.
Key Clinical Implications:
No hypertonic saline needed: The corrected sodium is normal, so isotonic (0.9%) saline is appropriate for initial fluid resuscitation if the patient requires treatment for hyperglycemia 1
Expected sodium rise with treatment: As glucose normalizes with insulin therapy, the measured sodium will rise toward the corrected value without additional sodium administration 2
Monitor for true hypernatremia: In hyperglycemic crises, particularly hyperosmolar hyperglycemic state (HHS), the corrected sodium can reveal significant hypernatremia requiring hypotonic fluid replacement 1, 2
Treatment Considerations Based on Glucose Level
With a glucose of 253 mg/dL and normal corrected sodium, management depends on clinical context 1:
For hospitalized non-critically ill patients: Target glucose 140-180 mg/dL; insulin therapy should be initiated if glucose persistently >180 mg/dL 1
For outpatients with new diagnosis: This glucose level warrants evaluation for diabetes, with HbA1c confirmation and consideration of oral agents like metformin if appropriate 3
Not a hyperglycemic crisis: This glucose level (253 mg/dL) is well below the threshold for diabetic ketoacidosis (>250 mg/dL with ketosis) or HHS (>600 mg/dL) 1, 4
Monitoring During Treatment
The corrected sodium should be recalculated as glucose falls to guide ongoing fluid management 2. A rising measured sodium during treatment is expected and appropriate as hyperglycemia resolves, provided the corrected sodium remains in normal range 1, 2.