Corrected Sodium Concentration

\[\begin{aligned} Na_{corr,classic} &= Na+1.6\left(\frac{Glu-100}{100}\right) \\ Na_{corr,modern} &= Na+2.4\left(\frac{Glu-100}{100}\right) \end{aligned}\]

Variables

NaCorrClassic[Nacorr classic]corrected sodium concentration using the classic 1.6 correction factor (mEq/L)

NaCorrModern[Nacorr modern]corrected sodium concentration using the modern 2.4 correction factor (mEq/L)

Na[Na⁺]measured serum sodium concentration (mEq/L)

Gluserum glucose concentration (mg/dL)

Description

What is this formula?

The Corrected Sodium Concentration formula estimates the serum sodium concentration adjusted for hyperglycemia. Elevated glucose causes water to move from the intracellular space into the extracellular space, producing dilutional hyponatremia.

When to use it

Use this formula when evaluating hyperglycemia, diabetic ketoacidosis, hyperosmolar hyperglycemic state, or hyponatremia associated with elevated serum glucose.

Example

Data:

Na = 130 mEq/L

Glu = 500 mg/dL

Formula:

Nacorr classic = Na + 1.6 × ((Glu − 100) / 100)

Nacorr modern = Na + 2.4 × ((Glu − 100) / 100)

Substitution:

Nacorr classic = 130 + 1.6 × ((500 − 100) / 100)

Nacorr classic = 136.4 mEq/L

Nacorr modern = 130 + 2.4 × ((500 − 100) / 100)

Nacorr modern = 139.6 mEq/L

Result:

The corrected sodium concentration is 136.4 mEq/L using the classic correction factor and 139.6 mEq/L using the modern correction factor.

Applications

- Hyperglycemia assessment

- Diabetic ketoacidosis

- Hyperosmolar hyperglycemic state

- Electrolyte interpretation

- Emergency medicine

Note

This formula is a clinical approximation. The classic correction factor of 1.6 mEq/L per 100 mg/dL of glucose above 100 mg/dL is the historically most widely taught version. A modern correction factor of 2.4 mEq/L is also widely cited, especially in marked hyperglycemia. The result should be interpreted together with clinical status, measured osmolality, hydration, and the rate of glucose correction.