- Select the glucose unit that matches your lab report — mg/dL (Philippines standard) or mmol/L (SI, used in some hospitals). Switching units clears the glucose field.
- Enter the measured serum sodium from the same blood draw (in mEq/L, which equals mmol/L). This is the uncorrected value as printed on the lab report.
- Enter the plasma glucose from the same blood draw. If glucose is below 100 mg/dL (5.6 mmol/L) the correction is negligible and near zero.
- Results appear automatically: the Hillier-corrected sodium (preferred), the Katz-corrected sodium (classic reference), and a status badge (Pseudohyponatremia / True hyponatremia / Masked hypernatremia / Normal).
- Read the plain-language verdict and the recommended next step, then share with your physician for clinical decision-making.
All computation runs in your browser; no values are stored or transmitted.
When to Use
Use this tool whenever a patient has a simultaneously elevated blood glucose and a low or borderline serum sodium. Hyperglycemia draws intracellular water into the extracellular space, diluting sodium and producing a falsely low lab reading — a phenomenon called translocational or dilutional pseudohyponatremia. Without correcting for glucose, a low sodium may trigger an unnecessary hyponatremia workup or inappropriate sodium supplementation.
Appropriate population
Any patient with a concurrent hyperglycemia (blood glucose above 100 mg/dL / 5.6 mmol/L) and a measured serum sodium below or at the low-normal range. Most relevant in diabetic ketoacidosis (DKA), hyperosmolar hyperglycemic state (HHS), poorly controlled type 1 or type 2 diabetes, and post-operative patients on glucose-containing fluids. In CKD and dialysis patients, hyperglycemia is common, and the glucose effect on sodium can compound an already complex fluid and electrolyte picture.
When NOT to rely on correction alone
If the glucose-corrected sodium is still low (below 135 mEq/L), this is genuine hyponatremia that co-exists with the hyperglycemia — it will not resolve on its own when glucose is treated and needs its own evaluation (volume status, urine studies, medications, SIADH). This calculator does not replace clinical assessment of volume status, urine osmolality, or urine sodium. Never correct sodium rapidly (>8–10 mEq/L per 24 hours) without close physician supervision to avoid osmotic demyelination.
Pearls & Pitfalls
Use Hillier 2.4 as the primary estimate
The Hillier factor of 2.4 is more accurate than the classic Katz 1.6, especially when glucose is above 400 mg/dL (22.2 mmol/L). At extreme hyperglycemia (glucose 800–1200 mg/dL in HHS), using only 1.6 can underestimate the corrected sodium by 5–7 mEq/L — a clinically important error when deciding whether a patient has true hyponatremia or masked hypernatremia.
Watch the sodium rise as glucose is treated
In DKA and HHS, the measured sodium typically rises as insulin therapy lowers glucose. If the corrected sodium is already at the high-normal or above-normal range, a rapid fall in glucose may unmask significant hypernatremia — recheck sodium frequently (every 1–2 hours in ICU-level care) and replace free water (hypotonic fluids) appropriately. The target is a gradual sodium correction, not a rapid one.
Pitfalls
(1) Do not dismiss a low sodium as "just glucose" without applying the correction — true hyponatremia can co-exist with hyperglycemia (e.g., a patient who has been vomiting and drinking free water). (2) In CKD and dialysis patients, sodium derangements interact with fluid overload and ultrafiltration goals — always involve the nephrology team. (3) Lipemia or severe hyperproteinemia can cause pseudohyponatremia by a different mechanism (exclusion artifact), which this formula does not correct for — use direct-reading (ISE-undiluted) sodium methods when both hyperglycemia and extreme lipemia/protein are present.
Why Use It
Glucose is an osmotically active solute that does not freely cross cell membranes in most tissues. When plasma glucose rises, osmotic pressure draws water out of cells into the extracellular compartment — diluting the serum sodium by roughly 1.6 to 2.4 mEq/L for every 100 mg/dL (5.6 mmol/L) rise in glucose above normal. The original Katz correction factor of 1.6 (from a 1973 case series) has been widely used, but a prospective study by Hillier et al. (1999) found a mean correction factor of 2.4 — with the higher factor being more accurate especially when glucose exceeds 400 mg/dL. Using only the Katz factor can underestimate the true corrected sodium by several mEq/L at very high glucose levels, potentially masking hypernatremia or over-calling hyponatremia in DKA and HHS.
In CKD patients — who often have diabetes as the primary cause of kidney disease — hyperglycemia-induced pseudohyponatremia is a clinically important electrolyte mirage. Misinterpreting it as true hyponatremia can delay appropriate treatment (insulin and glucose-lowering) and lead to inappropriate fluid or sodium management that further strains the already-limited fluid tolerance of CKD kidneys.
Sodium Correction for Hyperglycemia — Is the Low Sodium Real?
Enter measured serum sodium and blood glucose (mg/dL or mmol/L). Both the Hillier 2.4 and Katz 1.6 corrected values are shown, with a plain-language interpretation.
⚕ Corrected Na = measured Na + factor × ((glucose − 100) ÷ 100). Katz factor = 1.6 (classic); Hillier factor = 2.4 (more accurate, especially when glucose >400 mg/dL). This estimate guides interpretation only — it does not replace clinical assessment. Sodium and glucose disturbances need physician evaluation; never correct sodium rapidly on your own.
Next Steps
Use the result to support — not replace — clinical judgment.
- Interpret the value against the targets shown in the calculator and the Evidence section below, in the context of the full clinical picture.
- Trend serial measurements rather than acting on a single result; confirm abnormal or unexpected values before changing management.
- Apply the relevant KDIGO / specialty-guideline threshold and document the indication.
- Escalate or refer to nephrology when results are out of range, rapidly changing, or discordant with the clinical picture — and discuss the implications with the patient.
Evidence & References
Formula & Equations
| Method | Correction Factor | Formula |
|---|---|---|
| Hillier (1999) — preferred | 2.4 mEq/L per 100 mg/dL glucose above normal | Corrected Na = Measured Na + 2.4 × ((Glucose − 100) ÷ 100) |
| Katz (1973) — classic | 1.6 mEq/L per 100 mg/dL glucose above normal | Corrected Na = Measured Na + 1.6 × ((Glucose − 100) ÷ 100) |
| SI conversion | 1 mmol/L glucose = 18 mg/dL | Multiply mmol/L × 18 before applying formula above |
Corrected sodium interpretation bands
| Corrected Na (Hillier) | Status | Clinical Implication |
|---|---|---|
| < 135 mEq/L | True hyponatremia | Low sodium persists after glucose correction — needs independent hyponatremia workup (volume status, urine Na, urine osmolality, medications) |
| 135–145 mEq/L, measured < 135 | Pseudohyponatremia | Low lab reading is driven by glucose; sodium will normalize as glucose falls with insulin treatment — no sodium-specific therapy usually needed |
| 135–145 mEq/L, measured normal | Normal | No sodium derangement is being masked; manage hyperglycemia as indicated |
| > 145 mEq/L | Masked hypernatremia | True free-water deficit hidden by glucose dilution; measured sodium will rise toward corrected value as glucose falls — treat the water deficit |
The Hillier value is used for status classification because it is more accurate at glucose levels above 400 mg/dL — the range most commonly seen in DKA and HHS — where the Katz factor consistently underestimates the correction.
Evidence & References
The Katz 1.6 correction factor was derived from a small physiological study of healthy subjects given hypertonic glucose infusions and has been the default teaching formula since 1973. Hillier et al. prospectively re-evaluated the correction factor in 2,173 patients with simultaneous glucose and sodium measurements across a broad glycemic range and found a mean factor of 2.4, which better reflects real-world clinical data — particularly at higher glucose concentrations. The 2.4 factor is now endorsed by major endocrinology and nephrology guidelines for DKA/HHS management.
- Hillier TA, Abbott RD, Barrett EJ. Hyponatremia: evaluating the correction factor for hyperglycemia. Am J Med. 1999;106(4):399–403.
- Katz MA. Hyperglycemia-induced hyponatremia — calculation of expected serum sodium depression. N Engl J Med. 1973;289(16):843–844.
- Kitabchi AE, Umpierrez GE, Miles JM, Fisher JN. Hyperglycemic crises in adult patients with diabetes. Diabetes Care. 2009;32(7):1335–1343.
- Weisberg LS. Pseudohyponatremia: a reappraisal. Am J Med. 1989;86(3):315–318.
