This calculator is deliberately not a medical device
The corrected sodium result is an educational estimate based on published formulas. It must not be used as a standalone diagnosis, treatment order, admission decision, discharge decision, fluid selection rule, insulin protocol, or substitute for a qualified clinician. In hyperosmolar hyperglycemic state, diabetic ketoacidosis, severe hyponatremia, hypernatremia, seizures, coma, shock, renal failure, or pregnancy, interpretation requires urgent clinical assessment and local regulated protocols.
Corrected sodium calculation at a glance
Katz formula: corrected Na = measured Na + 0.016 x (glucose mg/dL - 100).
Hillier modified approach: when glucose is above 400 mg/dL, use 0.024 x (glucose mg/dL - 100).
SI glucose: glucose mmol/L is converted to mg/dL before applying the published correction factor.
Sodium units: mEq/L and mmol/L are numerically equivalent for sodium.
# Why hyperglycemia lowers measured sodium
Marked hyperglycemia increases extracellular tonicity. Water moves from the intracellular compartment into the extracellular compartment, expanding extracellular water and diluting measured serum sodium. The sodium concentration may look low even when the total body sodium deficit, water deficit, and effective osmolality tell a more complex story. This is often described as translocational or hypertonic hyponatremia rather than true hypotonic hyponatremia.Correcting sodium for glucose is therefore a way to ask a narrow question: what sodium concentration would be expected if the glucose-related osmotic water shift were removed from the measurement? The answer can change the clinical framing. A measured sodium of 128 mEq/L with glucose 600 mg/dL may correct into the normal range, which points away from treating the number as isolated hypotonic hyponatremia.- Measured sodium
- The sodium concentration reported by the laboratory at the current glucose level.
- Corrected sodium
- An estimated sodium concentration adjusted for glucose-related dilution.
- Effective osmolality
- Osmoles that sustain water movement across cell membranes, mainly sodium salts and glucose.
- Katz factor
- Classic 1.6 mEq/L sodium correction for every 100 mg/dL glucose above 100 mg/dL.
- Hillier factor
- A larger correction factor, often simplified as 2.4 mEq/L per 100 mg/dL, especially in marked hyperglycemia.
| Input | Accepted units | How it is used | Common pitfall |
|---|---|---|---|
| Serum sodium | mEq/L or mmol/L | Starting value for correction | Treating corrected sodium as a fluid order |
| Glucose | mg/dL or mmol/L | Converted to mg/dL for Katz or Hillier formula | Mixing mmol/L with mg/dL formula |
| Correction factor | 1.6 or 2.4 per 100 mg/dL | Determines sodium added above glucose 100 mg/dL | Using 2.4 automatically at all glucose values |
# Katz versus Hillier correction factors
Katz described an expected fall in serum sodium of about 1.6 mEq/L for every 100 mg/dL rise in glucose above 100 mg/dL. This factor became widely taught because it is simple and clinically memorable. The formula is often written as corrected sodium equals measured sodium plus 0.016 times glucose minus 100, with glucose in mg/dL.Hillier and colleagues later evaluated the relationship experimentally and found that the average change was larger, about 2.4 mEq/L per 100 mg/dL, with particular relevance at higher glucose levels. Many clinical summaries use the classic factor for modest hyperglycemia and the larger factor when glucose exceeds 400 mg/dL. This calculator mirrors that practical split in its Hillier modified option.Katz classic
Uses 1.6 mEq/L per 100 mg/dL above 100 mg/dL at all glucose levels.
- Simple bedside arithmetic
- Conservative correction in extreme hyperglycemia
- Still widely cited in teaching material
Hillier modified
Uses 1.6 until glucose is above 400 mg/dL, then applies 2.4 mEq/L per 100 mg/dL.
- Better reflects marked hyperglycemia in the source study
- Often changes classification when glucose is very high
- Requires careful communication in notes and handoffs
100 mg/dL baseline glucose in the formula
1.6 Katz mEq/L per 100 mg/dL
2.4 Hillier mEq/L per 100 mg/dL
400 mg/dL threshold for modified factor here
# How to read a corrected sodium result
A corrected sodium below 135 mEq/L suggests that hyponatremia may persist even after accounting for hyperglycemia. A corrected sodium between 135 and 145 mEq/L suggests the apparent low sodium may be largely explained by glucose-driven water movement. A corrected sodium above 145 mEq/L suggests a hypernatremic tendency after correction, often pointing toward a significant free water deficit in severe hyperglycemic illness. These are descriptive categories, not treatment instructions.Do not correct sodium too quickly because a calculator number changed the label
Osmotic demyelination risk, cerebral edema risk, potassium shifts, insulin effects, renal replacement therapy, and ongoing urinary water losses all matter. Corrected sodium helps interpretation, but serial measured sodium, glucose fall rate, effective osmolality, neurologic status, and local DKA/HHS protocols govern bedside decisions.
- Compare measured and corrected sodium: the gap between them reflects the glucose-related adjustment.
- Look at effective osmolality: sodium and glucose together better describe tonicity than sodium alone.
- Track direction over time: corrected sodium rising during treatment may suggest water deficit or inadequate free water replacement.
- Check potassium before insulin decisions: hyperglycemic crisis protocols often prioritize potassium safety.
- Document the factor: Katz and Hillier can produce meaningfully different values at high glucose.
Example calculation
If measured sodium is 128 mEq/L and glucose is 600 mg/dL, Katz adds 0.016 x 500 = 8.0 mEq/L, giving corrected sodium 136.0 mEq/L. Hillier modified adds 0.024 x 500 = 12.0 mEq/L because glucose is above 400 mg/dL, giving corrected sodium 140.0 mEq/L. The difference is clinically noticeable, so the chosen factor should be explicit.
# Unit conversion details
The original formulas are commonly expressed with glucose in mg/dL. When glucose is entered in mmol/L, this calculator converts it to mg/dL using the glucose molecular weight conversion. A glucose of 10 mmol/L is about 180 mg/dL, so the correction applies only to the increment above the formula baseline of 100 mg/dL.| Glucose | Approximate mg/dL | Increment above 100 | Katz correction |
|---|---|---|---|
| 10 mmol/L | 180 mg/dL | 80 mg/dL | +1.3 mEq/L |
| 20 mmol/L | 360 mg/dL | 260 mg/dL | +4.2 mEq/L |
| 30 mmol/L | 541 mg/dL | 441 mg/dL | +7.1 mEq/L |
| 40 mmol/L | 721 mg/dL | 621 mg/dL | +9.9 mEq/L |
Use the same glucose sample time as the sodium sample
Glucose can change quickly after insulin, fluids, or dextrose. A sodium from one time point and glucose from another can produce a corrected sodium that never represented the patient at a single moment.# Regulatory and clinical boundaries
Clinical calculators that return individualized outputs from patient data can be regulated as software as a medical device depending on jurisdiction, intended use, claims, integration, and risk. This page is written and labeled as an educational arithmetic demonstrator. It intentionally avoids diagnosis, treatment recommendations, patient-specific instructions, or claims of safety or effectiveness.Strengths and limitations
Advantages
- Makes the sodium-glucose relationship visible and easy to teach.
- Allows explicit comparison of Katz and Hillier factors.
- Supports mg/dL and mmol/L glucose entry.
- Highlights that apparent hyponatremia can be dilutional in hyperglycemia.
Disadvantages
- Does not assess volume status, symptoms, renal function, or treatment risk.
- Different institutions may standardize a different factor or protocol.
- Cannot verify laboratory timing, sample quality, or transcription errors.
- Does not replace measured osmolality or full electrolyte interpretation.
Clinical bottom line
Corrected sodium is a context tool, not a decision engine. It helps clinicians understand sodium in the presence of hyperglycemia, but safe care depends on the complete patient picture, serial labs, effective osmolality, treatment protocols, and accountable clinical judgment.