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Sodium Correction Calculator for Hyperglycemia

Estimate corrected serum sodium when glucose is elevated. Enter measured sodium (mEq/L) and plasma glucose (mg/dL). Both the Katz 1973 and Hillier 1999 correction factors are shown.

Inputs

Katz 1973 formula: corrected Na = measured Na + 0.016 x (glucose - 100). Hillier 1999 variant uses 0.024. Both are shown below.

Result

Corrected Na (Katz, 0.016)--
Corrected Na (Hillier, 0.024)--
Glucose above 100--

Normal sodium reference range is 135 to 145 mEq/L. This calculator applies the correction for hyperglycemia only. It does not diagnose or treat any condition.

Katz 1973 / Hillier 1999 factorsNEJM & American Journal of MedicineCalculates client side
Naomi Foster
By Naomi Foster, health writer. Last updated .

What This Correction Means

High plasma glucose draws water out of cells and into the bloodstream, diluting serum sodium. The sodium measured by the lab in that setting is lower than the patient's true sodium at normal glucose. The correction formula estimates what sodium would be if glucose were at a normal baseline of 100 mg/dL.

Katz 1973 formula. Corrected sodium (mEq/L) = measured sodium + 0.016 x (glucose - 100). For every 100 mg/dL rise in glucose above 100, sodium is adjusted upward by approximately 1.6 mEq/L.
Hillier 1999 variant. Corrected sodium (mEq/L) = measured sodium + 0.024 x (glucose - 100). This coefficient (0.024) was derived from a more recent study and may give a better estimate at very high glucose values, particularly above 400 mg/dL.

For example: measured sodium 130 mEq/L, glucose 400 mg/dL. Katz: 130 + 0.016 x (400 - 100) = 130 + 4.8 = 134.8 mEq/L. Hillier: 130 + 0.024 x 300 = 130 + 7.2 = 137.2 mEq/L. The difference can be clinically meaningful at high glucose levels.

Which formula to use

The 0.016 factor (Katz 1973) appears in many textbooks and is the most widely cited. The 0.024 factor (Hillier 1999) is supported by a laboratory study that measured the actual change in sodium at multiple glucose concentrations. Several references note that the Katz formula underestimates the correction at severe hyperglycemia. This calculator shows both values. The choice is a clinical judgment.

Source

Original formula: Katz MA. "Hyperglycemia-Induced Hyponatremia: Calculation of Expected Serum Sodium Depression." New England Journal of Medicine, 1973;289(16):843-844. Revised coefficient: Hillier TA, Abbott RD, Barrett EJ. "Hyponatremia: evaluating the correction factor for hyperglycemia." American Journal of Medicine, 1999;106(4):399-403. See the MDCalc sodium correction reference for further context.

Related Calculators for Electrolyte and Kidney Values

Hyperglycemia and sodium disorders frequently coexist with kidney disease. See the CKD-EPI kidney function estimator for one piece of that picture, and the albumin-adjusted calcium tool for another electrolyte correction used in the same setting.

One thing this cannot do. Neither correction factor shown here replaces bloodwork read by a clinician who knows the rest of your chart.
What people ask about sodium correction

Sodium FAQs

What is the formula for corrected sodium in hyperglycemia?

The Katz 1973 formula is: corrected sodium (mEq/L) = measured sodium + 0.016 x (glucose - 100). A variant published by Hillier and colleagues in 1999 uses a coefficient of 0.024 instead of 0.016. The Hillier factor may give a closer estimate at very high glucose levels.

Why does high blood glucose lower sodium?

High glucose draws water from cells into the extracellular space by osmosis. This additional water dilutes plasma sodium, making the measured sodium appear lower than it would be at normal glucose. When glucose returns to normal, sodium rises back toward its corrected value.

Which sodium correction formula should I use?

The 0.016 factor (Katz 1973) is historically the most widely cited. The 0.024 factor (Hillier 1999) was derived from a study showing the Katz factor may underestimate the correction at very high glucose levels. This calculator shows both. Which to apply is a clinical decision.

What is a normal serum sodium level?

Normal serum sodium is generally 135 to 145 mEq/L. Values below 135 are hyponatremia and above 145 are hypernatremia. In hyperglycemia, measured sodium may be artificially low, so the corrected value helps assess whether true hyponatremia exists.