Sodium Corrected by Glucose

Sodium Correction for Hyperglycemia

When blood glucose runs very high, water gets pulled out of the cells into the extracellular space. That dilutes plasma sodium and leaves you with translocational (dilutional) hyponatremia. The reading on the panel then undershoots the patient's true tonicity. The Hillier formula (Hillier et al., 1999, a prospective hypertonic clamp study) estimates the “true” sodium you would see once glucose came back to normal: Na_corr = Na_measured + 2.4 × (glucose − 100) / 100, with glucose in mg/dL.

The older Katz factor of 1.6 (1973) tends to undershoot the correction, which is why it has mostly fallen out of use. The American Diabetes Association (ADA) 2024 standards and most endocrinology references back the Hillier coefficient of 2.4. One caveat before you change therapy: rule out pseudo-hyponatremia from severe hyperlipidemia or hyperproteinemia first.

Applications

Think diabetic ketoacidosis (DKA), hyperosmolar hyperglycemic state (HHS), uncontrolled type 2 diabetes turning up in the emergency department, perioperative hyperglycemia, and pediatric DKA, where rapid swings in sodium raise the risk of cerebral edema. The corrected value helps you pick the fluid (0.9% vs 0.45% saline) and decide how fast to bring glucose down.

FAQ

When should I apply the correction? Technically any time serum glucose climbs past 100 mg/dL, though it only starts to matter clinically above roughly 200 mg/dL. Under that, the adjustment disappears into ordinary laboratory noise.

Why is Hillier preferred over Katz? Katz worked from a linear theoretical model. Hillier went and measured what actually happened in healthy volunteers given hypertonic dextrose, and the in vivo factor came out nearer 2.4 mEq/L for every 100 mg/dL rise in glucose.

Is this a substitute for medical judgement? No. It is an educational calculator, not a stand-in for clinical evaluation, laboratory confirmation, or your institution's protocols. Read the result alongside osmolality, anion gap, and the patient's fluid status.