Corrected Sodium & Effective Serum Osmolality Calculator
Corrected sodium (Katz & Hillier) and effective osmolality using measured sodium and glucose
Result
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Overview of Effective Osmoles
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Definition: Effective osmoles are solutes that do not freely cross cell membranes and therefore exert osmotic pressure, pulling water out of the cells.
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The Role of Glucose: Because insulin is deficient in DKA, glucose cannot effectively enter cells and acts as an osmotically active solute, causing intracellular dehydration.
Formula
Glucose in mg/dL
Katz: Corrected Na = Na + 0.016 × (glucose − 100)
Hillier: Corrected Na = Na + 0.024 × (glucose − 100)
Effective serum osmolality = 2 × Na + (glucose / 18)
Glucose in mmol/L
Katz: Corrected Na = Na + 1.6 × ((glucose − 5.5) / 5.5)
Hillier: Corrected Na = Na + 2.4 × ((glucose − 5.5) / 5.5)
Effective serum osmolality = 2 × Na + glucose
References
1) Katz MA. Hyperglycemia-induced hyponatremia—calculation of expected serum sodium depression. N Engl J Med. 1973;289(16):843–844. PMID: 4763428
2) Hillier TA, Abbott RD, Barrett EJ. Hyponatremia: evaluating the correction factor for hyperglycemia. Am J Med. 1999;106(4):399–403. PMID: 10225241
3) Kitabchi AE, et al. Management of hyperglycemic crises in patients with diabetes. Diabetes Care. 2001;24(1):131–153. doi:10.2337/diacare.24.1.131. PMID: 11194218
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