This sodium correction calculator adjusts measured sodium for hyperglycemia — high glucose pulls water into the blood and dilutes sodium, printing a falsely low number called translocational hyponatremia.
Corrected Na = Measured Na + Factor × (Glucose − 100) ÷ 100
Glucose joins sodium in the tonicity arithmetic of our Serum Osmolality Calculator — the two pages read the same physiology from different ends. Part of our Health Calculators collection.
Worked Example (Verified)
- Na 128, glucose 500 (defaults): excess glucose = 4 units → Katz: 128 + 6.4 = 134.4; Hillier: 128 + 9.6 = 137.6 — the “severe hyponatremia” is largely dilution; the true tonicity problem is the glucose
- At glucose 200 the correction shrinks to +1.6/+2.4 — it scales with the sugar, as it should
- Clinical use in DKA/HHS: as insulin lowers glucose, measured Na should rise toward the corrected figure; failure to rise signals true sodium/water imbalance needing its own management
- Correction-rate guardrails for true hyponatremia (≤ 8–10 mEq/L per 24 h to avoid osmotic demyelination) apply to the corrected interpretation, not the raw printout
Not All Low Sodium Is Dilution
- Pseudohyponatremia: severe hypertriglyceridemia/paraproteinemia fools indirect electrode assays — a lab artifact, not water shift; direct ISE resolves it.
- True hypotonic hyponatremia (SIADH, thiazides, adrenal issues) is a different diagnosis with a normal glucose — this correction doesn’t apply.
- Other effective osmoles (mannitol) cause the same translocation trick as glucose.
- Track the trend through treatment, not a single corrected snapshot.
Related Tools
- Serum Osmolality Calculator — tonicity and the osmolal gap
- Anion Gap Calculator — the DKA companion number
- Health Calculators — the full collection
Frequently Asked Questions
How do you correct sodium for glucose?
Add 1.6 mEq/L (Katz) — or 2.4 (Hillier) — to the measured sodium for every 100 mg/dL of glucose above 100. Na 128 at glucose 500 corrects to 134.4 (Katz) or 137.6 (Hillier). This calculator reports both conventions.
Why does high glucose lower measured sodium?
Glucose is an effective osmole: it holds water in the extracellular space, pulling water out of cells until tonicity equalizes. The extra water dilutes sodium concentration — total body sodium may be normal while the printed value is low (translocational hyponatremia).
Katz 1.6 or Hillier 2.4 — which should I use?
Katz’s 1.6 (1973) is the traditional textbook factor; Hillier’s 2.4 (1999) matched measured changes better, especially above glucose ~400 mg/dL. Reporting both, as here, brackets the plausible corrected range; clinical protocols usually name their chosen factor explicitly.
What does the corrected sodium predict?
The sodium value expected once glucose returns to ~100 mg/dL, assuming water and sodium balances otherwise hold. In DKA/HHS management it separates “sodium that will fix itself with insulin” from true sodium disorders riding alongside.
How fast can hyponatremia be corrected safely?
For true chronic hyponatremia, generally no faster than ~8–10 mEq/L in 24 hours (4–6 in high-risk patients) to avoid osmotic demyelination. Glucose-driven dilution resolves as glucose falls — one reason the corrected figure, not the raw one, anchors the plan.
Is this sodium correction calculator free?
Yes — free, instant, no sign-up. An educational/clinical aid; treatment decisions belong to the treating team.