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Sodium Correction Calculator

Calculate corrected serum sodium in the setting of hyperglycemia using the Hillier or Katz formula, with classification of hypo- and hypernatremia.

The Hillier formula (2018) is today's standard. Katz (1973) is legacy and underestimates correction.

Reference ranges (corrected sodium)

Hyponatremia

True hyponatremia after correction

< 135 mEq/L
Normal

Eunatremia

135 – 145 mEq/L
Hypernatremia

Free-water deficit, hypertonic dehydration

> 145 mEq/L

Note: this calculator is an educational tool and is not a substitute for medical advice. For healthcare professional reference only.

Frequently Asked Questions

When do I need to correct sodium for hyperglycemia?+
Whenever serum glucose exceeds 200 mg/dL (11.1 mmol/L) and sodium is abnormal. High glucose draws water into the extracellular space and dilutes sodium by roughly 2.4 mEq/L for every 100 mg/dL above 100 mg/dL (Hillier formula).
Hillier vs Katz — which formula is more accurate?+
The Hillier formula (2018) is based on hypertonic glucose-infusion experiments and uses a factor of 2.4. The older Katz formula (1973) uses 1.6 and underestimates the correction; it is largely abandoned today.
What is pseudohyponatremia?+
Apparent hyponatremia caused by hyperglycemia, hyperlipidemia, or hyperproteinemia. Once corrected, sodium is normal — there is no true sodium deficit. Classic in diabetic ketoacidosis (DKA).
How do I convert glucose from mmol/L to mg/dL?+
1 mmol/L glucose = 18.0182 mg/dL. Example: 22.2 mmol/L × 18 ≈ 400 mg/dL. The calculator accepts both units.
What sodium values define hyponatremia?+
Serum sodium < 135 mEq/L. Severity: mild 130–134, moderate 125–129, severe < 125 mEq/L. Levels below 120 mEq/L are a medical emergency.
Does this calculator replace clinical assessment?+
No. Sodium correction is a tool for the differential diagnosis of hyponatremia and must be interpreted alongside volume status, serum osmolality, urine sodium, and clinical exam.

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Sodium Correction Calculator — Hyperglycemia and Pseudohyponatremia

8 min