Fractional Excretion of Sodium Calculator

You must use the same unit for plasma and urine sodium, and the same unit for plasma and urine creatinine.


Fraction excreted: %

Fractional Excretion of Sodium

The sodium level in urine and blood makes it possible to diagnose the nephrotic syndrome, kidney disease, kidney damage, etc.

Fractional sodium excretion is therefore calculated taking into account sodium and creatinine in urine and plasma.

To obtain these values, it is, therefore, necessary to do:

blood test,

and urine test.

Sodium Excretion Fraction Interpretation

If the sodium excretion fraction is less than 1%, it may be prerenal insufficiency.

This dysfunction of the kidneys is due to insufficient blood flow.

How is the Fractional Excretion of Sodium calculated?


The amount of sodium excreted is calculated by multiplying the sodium concentration in urine by the urine output. This is the numerator in the equation. The denominator is the total amount of sodium filtered by the kidneys. This is calculated by multiplying the plasma sodium concentration by the glomerular filtration rate calculated using creatinine filtration. This formula is represented mathematically by:

[( Urinary sodium × Urinary output ) ÷ (( Plasma sodium ) × (( Urinary creatinine × Urinary output ) ÷ ( Plasma creatinine )))] × 100