Accurate sodium correction in hyperglycemia is critical to avoid misdiagnosing pseudohyponatremia, a condition where high blood glucose artificially lowers serum sodium levels. This guide provides healthcare professionals and medical students with actionable formulas (Katz and Hillier), step-by-step calculations, and clinical examples to determine true sodium levels in patients with diabetic ketoacidosis (DKA), hyperosmolar hyperglycemic state (HHS), or severe hyperglycemia. Patients can also understand why sodium levels may appear abnormal during glucose spikes and the importance of timely medical intervention. Learn how to adjust for glucose’s osmotic effect, interpret corrected values, and apply this knowledge to improve fluid management and treatment outcomes.
What is Sodium Correction in Hyperglycemia?
High blood glucose (hyperglycemia) draws water into the bloodstream, diluting sodium levels and causing pseudohyponatremia (falsely low sodium). Correction formulas adjust for this osmotic shift to reveal the true sodium concentration, ensuring accurate diagnosis and treatment in conditions like diabetic ketoacidosis (DKA) or hyperosmolar hyperglycemic state (HHS).
When to Correct Sodium
- Glucose > 200 mg/dL (11.1 mmol/L).
- Suspected DKA or HHS.
- Unexplained hyponatremia with elevated glucose.
Correction Formulas
Two evidence-based methods:
| Formula | Equation | Glucose Units | Adjustment per 100 mg/dL Glucose ↑ |
|---|---|---|---|
| Katz | Corrected Na⁺ = Na⁺ + 0.024 × (Glucose − 100) | mg/dL | +2.4 mEq/L |
| Hillier | Corrected Na⁺ = Na⁺ + 0.016 × (Glucose − 100) | mg/dL | +1.6 mEq/L |
For SI Units (mmol/L):
- Katz: Replace
0.024with 1.4. - Hillier: Replace
0.016with 0.92.
🧮 Sodium Correction for Hyperglycemia
📐 Correction Formulas Used:
- 🧮 Katz (mg/dL): Na⁺ + 0.024 × (Glucose - 100)
- 🧮 Hillier (mg/dL): Na⁺ + 0.016 × (Glucose - 100)
- 🧪 Katz (mmol/L): Na⁺ + 1.4 × (Glucose - 5.5)
- 🧪 Hillier (mmol/L): Na⁺ + 0.92 × (Glucose - 5.5)
🖊️ Enter Your Values:
Step-by-Step Calculation
- Obtain Labs: Serum Na⁺ and glucose (mg/dL or mmol/L).
- Apply Formula:
- Example (Katz, mg/dL):
- Na⁺ = 130 mEq/L, Glucose = 500 mg/dL.
- Corrected Na⁺ = 130 + 0.024 × (500 − 100) = 139.6 mEq/L (normal).
- Interpret:
- Normal Range: 135–145 mEq/L.
- <135 mEq/L post-correction: True hyponatremia (investigate further).
Clinical Guidelines for Providers
- DKA/HHS Management:
- Use corrected sodium to guide fluid resuscitation (e.g., 0.9% saline vs. balanced solutions).
- Monitor sodium closely during insulin therapy to avoid rapid shifts (risk of cerebral edema).
- Formula Selection:
- Katz: Preferred for severe hyperglycemia (e.g., glucose > 400 mg/dL).
- Hillier: Conservative estimate for mild-moderate cases.
Patient-Friendly Explanation
- Why Sodium Appears Low: High glucose pulls water into blood, diluting sodium.
- What Corrected Sodium Means: Reflects true sodium levels after accounting for glucose’s effect.
- Action Steps: Follow your care team’s advice on insulin, fluids, and repeat blood tests.
Quick Reference Table
| Glucose (mg/dL) | Katz Adjustment | Hillier Adjustment |
|---|---|---|
| 200 | +2.4 | +1.6 |
| 300 | +4.8 | +3.2 |
| 400 | +7.2 | +4.8 |
| 500 | +9.6 | +6.4 |
Limitations & Pitfalls
- Extreme Hyperglycemia (>1000 mg/dL): Formulas may underestimate correction.
- Other Osmoles: Mannitol, glycine, or ethanol require separate adjustments.
- Pseudonormonatremia: Normal corrected Na⁺ may mask underlying electrolyte disorders.
Key Takeaways
✅ Providers: Always correct sodium in hyperglycemia to avoid fluid mismanagement.
✅ Students: Memorize Katz formula (0.024 × glucose) for exams and clinical rotations.
✅ Patients: High glucose skews sodium results—regular monitoring is critical.
