Sodium Correction for Hyperglycemia: Adjusts measured sodium for the osmotic effect of glucose. Critical for IV fluid management in DKA/HHS.
Guidelines & Evidence
Clinical Details
Section 1
When to Use
When to Use
Evaluation of hyponatremia in patients with significant hyperglycemia (e.g., DKA, HHS).
Calculation of the "true" tonicity to guide fluid selection (0.45% vs 0.9% NaCl).
Assessment of total body water deficit in dehydrated diabetic patients.
The "Translational" Rule
This calculation identifies "translational hyponatremia"—a predictable drop in sodium caused by osmotic shifts rather than a true sodium deficiency.
Section 2
Formula & Logic
Physiological Rationale
Glucose is an effective osmole. When serum glucose rises, it increases extracellular tonicity, creating an osmotic gradient that draws water from the intracellular to the extracellular space. This influx of water dilutes the serum sodium concentration.
Standard Formula (Katz)
Corrected Na = Measured Na + [0.016 × (Glucose - 100)]
Alternative Notation
Corrected Na = Measured Na + [1.6 × (Glucose - 100) / 100]
Section 3
Pearls/Pitfalls
1.6 vs. 2.4 — Which Factor?
1.6 Factor (Katz): The traditional standard; highly reliable for glucose < 400 mg/dL.
2.4 Factor (Hillier): Evidence suggests that for severe hyperglycemia (> 400 mg/dL), a 2.4 correction factor better predicts the actual sodium change.
Severe HHS Caveat
If the corrected sodium is high (> 145 mEq/L) in a patient with HHS, it indicates severe total body water depletion and a high risk of cardiovascular collapse if not hydrated carefully.
Neurological Relevance
The corrected sodium provides a better correlate for the patient’s mental status. If a patient is comatose with a measured sodium of 128 but a corrected sodium of 142, the altered mental status is likely due to hyperosmolarity or acidosis rather than hyponatremic encephalopathy.
Section 4
Next Steps
Management Decisions
01
If Corrected Na < 135: Continue 0.9% NaCl if the patient is hypovolemic.
02
If Corrected Na is normal or high: Consider switching to 0.45% NaCl to address the water deficit.
03
Monitor: As glucose falls with insulin therapy, measured sodium should rise. If measured sodium stays flat while glucose drops, the patient is losing water or gaining sodium too rapidly.
Complementary Calculators
Free Water Deficit
Serum Osmolality
Anion Gap
Section 5
Evidence Appraisal
Foundational Reference
Hyperglycemia-induced hyponatremia—calculation of expected serum sodium depression.
Katz MA. • New England Journal of Medicine.. 1973;289(16):843-4. The original description of the 1.6 factor.
Modern Revision
Hyponatremia and hyperglucosemia: a reevaluation of the correction factor.
Hillier TA et al. • Diabetes Care.. 1999;Demonstrated that the 2.4 factor is more accurate at extreme glucose levels (> 400 mg/dL).
Section 6
Literature
Dr. Murray A. Katz
A nephrologist and professor of medicine whose 1973 letter to the NEJM remains one of the most cited clinical rules in electrolyte management. His work simplified the bedside approach to "pseudohyponatremia" (a term now largely replaced by translational hyponatremia in this context).
