Corrected Sodium Calculator – Sodium Correction for Glucose
Estimates corrected serum sodium in hyperglycemia using the Katz (1.6 mEq/L per 100 mg/dL) and Hillier (2.4 mEq/L) correction factors. Enter measured sodium and serum glucose to see both results.
Hyperglycemia Sodium Correction
Corrected Sodium Formula (Katz and Hillier)
Where:
- \(\text{Na}_{\text{measured}}\) — serum sodium from the laboratory report (mEq/L)
- \(\text{Glucose}\) — serum glucose in mg/dL (if measured in mmol/L, multiply by 18.0182 first)
- \(1.6\) — correction factor of Katz (1973), in mEq/L of sodium per 100 mg/dL of glucose above 100
- \(2.4\) — correction factor of Hillier (1999), in mEq/L per 100 mg/dL above 100
The first equation is the classic Katz correction; the second is the Hillier correction, which accounts for the stronger sodium–glucose relationship observed at very high glucose concentrations. Both express the same idea: for every 100 mg/dL that glucose rises above 100 mg/dL, serum sodium falls by a predictable amount because water is drawn out of cells into the extracellular space.
Corrected Sodium – Calculation Example
Example: a patient with diabetic ketoacidosis has a measured serum sodium of 130 mEq/L and a serum glucose of 600 mg/dL.
\[ \text{Katz:} \quad 130 + 1.6 \times \frac{600 - 100}{100} = 130 + 1.6 \times 5 = 138 \text{ mEq/L} \]
\[ \text{Hillier:} \quad 130 + 2.4 \times \frac{600 - 100}{100} = 130 + 2.4 \times 5 = 142 \text{ mEq/L} \]
Result: the corrected sodium is 138 mEq/L by the Katz method and 142 mEq/L by the Hillier method. Despite a measured sodium of 130 mEq/L suggesting hyponatremia, the corrected values show the true sodium status is normal or even elevated, which changes both diagnosis and fluid management.
How to use the calculator
- Enter the Measured sodium value from the patient's chemistry panel in mEq/L.
- Enter the Serum glucose value from the same or a recent blood draw.
- Select the correct Glucose unit — mg/dL or mmol/L. The calculator converts mmol/L to mg/dL automatically (multiply by 18.0182).
- Read both results: Corrected sodium (Katz, 1973) and Corrected sodium (Hillier, 1999), each in mEq/L.
- If the two values differ substantially, note that the gap widens at higher glucose levels and interpret both together with the clinical picture.
What is corrected sodium and why does it matter?
Corrected sodium estimates what the serum sodium would be if the elevated glucose were brought down to a normal level of about 100 mg/dL. High blood glucose creates an osmotic gradient that pulls water from the intracellular space into the blood vessels, diluting the sodium concentration in serum. This is called translocational hyponatremia: the measured sodium is low, but no sodium has actually been lost from the body.
The consequence is practical. In a hyperglycemic patient with a measured sodium of 130 mEq/L, the corrected value may be entirely normal. Treating such a patient with aggressive hypertonic saline would be a mistake; the correct treatment is insulin and fluids to lower glucose, after which the sodium will rise on its own — typically by about 1.6–2.4 mEq/L for every 100 mg/dL that glucose falls. Corrected sodium therefore prevents both over-treatment of
Frequently Asked Questions
Which correction factor should I use — Katz (1.6) or Hillier (2.4)?
The Katz factor of 1.6 mEq/L per 100 mg/dL is the classic standard and works well for most glucose levels. The Hillier factor of 2.4 mEq/L reflects a stronger correction observed at very high glucose, especially above 400 mg/dL, as seen in DKA or HHS. Many clinicians use Katz for moderate hyperglycemia and Hillier when glucose is very high. If unsure, calculate both and interpret them together with the clinical picture.
How do I convert glucose from mmol/L to mg/dL for the formula?
Multiply the glucose value in mmol/L by 18.0182 to get mg/dL. For example, a glucose of 25 mmol/L equals about 450 mg/dL. Sodium in mEq/L needs no conversion because mEq/L and mmol/L are numerically identical for sodium. The calculator performs the mmol/L to mg/dL conversion automatically, so you can simply select your glucose unit before entering the value.
What is a normal corrected sodium value?
A typical normal serum sodium range is roughly 135–145 mEq/L. After correction, a hyperglycemic patient's sodium should ideally fall within this range. A corrected value below 135 mEq/L suggests true hyponatremia with actual sodium deficit, while a value above 145 mEq/L suggests a free-water deficit, which is common in hyperosmolar hyperglycemic state. The corrected value, not the measured one, guides this interpretation.
Does the correction work in reverse — can I estimate sodium as glucose falls during treatment?
Yes. As insulin therapy lowers glucose, the osmotic gradient reverses and water moves back into cells, so measured sodium rises. For every 100 mg/dL that glucose falls, expect sodium to climb by roughly 1.6–2.4 mEq/L. This predicted rise can mask or reveal a true sodium deficit, so clinicians often track corrected sodium serially during treatment rather than relying on a single value.
Does the formula apply when glucose is below 100 mg/dL?
The formula is designed for hyperglycemia. If glucose is below 100 mg/dL, the term \((\text{Glucose} - 100)\) becomes negative and the calculator would subtract from sodium, which has no validated clinical meaning. Hypoglycemia does not cause translocational hyponatremia, so the correction should only be applied when glucose is genuinely elevated, typically above 200 mg/dL.
Can I use corrected sodium for other causes of hyponatremia, like heart failure or SIADH?
No. The Katz and Hillier corrections address only hyperglycemia-induced translocational hyponatremia, where water shifts dilute serum sodium. Hyponatremia from SIADH, heart failure, cirrhosis, diuretics, or adrenal insufficiency involves different mechanisms and requires its own workup. If a patient has low sodium with normal glucose, this calculator does not apply — consult clinical guidelines for those conditions.
Why does high glucose lower measured sodium if no sodium is lost?
Elevated glucose increases the osmolality of extracellular fluid, pulling water out of cells into the bloodstream. The extra water dilutes the plasma, so the sodium concentration reads low even though total body sodium is unchanged. This is called translocational or dilutional hyponatremia. Corrected sodium reverses this dilution mathematically, revealing the sodium status that will appear once glucose is normalized with treatment.