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Fractional Excretion of Sodium (FENa) Calculator

Distinguish prerenal vs intrinsic AKI.

Compute the fractional excretion of sodium (FENa) from urine and plasma sodium and creatinine. < 1% suggests prerenal AKI; > 2% suggests intrinsic (acute tubular necrosis).

Priya Venkatesan By Priya Venkatesan
Reviewed by Dr. Helena Ortiz
Published Last reviewed 1 min read

Inputs

mEq/L
mEq/L
mg/dL
mg/dL

Results

Enter values and click Calculate to see results.
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How to use this calculator

  1. Fill in the inputs above using the units you already have.
  2. Values update automatically as you type — no submit button needed.
  3. Hover any result row for the underlying formula and intermediate values.

Formula

FENa (%) = (U_Na · P_Cr) / (P_Na · U_Cr) × 100

In depth

Compute the fractional excretion of sodium (FENa) from urine and plasma sodium and creatinine. < 1% suggests prerenal AKI; > 2% suggests intrinsic (acute tubular necrosis).