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Fractional Excretion Of Sodium Calculator

Work out fractional excretion of sodium instantly with clear inputs, formula shown and shareable results.

About Fractional Excretion Of Sodium Calculator

Compares sodium clearance with creatinine clearance to judge whether the kidney is conserving sodium, the classic pre-renal versus intrinsic discriminator.

Formula

Fractional excretion of sodium

FENa (%) = (urine Na x plasma creatinine) / (plasma Na x urine creatinine) x 100

Worked example

With the default values below, Fractional Excretion Of Sodium Calculator returns Fractional excretion of sodium of 0.476%. Change any input above and every figure here is recalculated in your browser.

Inputs used

Urine sodiumaccepts 1–300 mmol/L
20 mmol/L
Plasma sodiumaccepts 100–180 mmol/L
140 mmol/L
Urine creatinineaccepts 5–400 mg/dL
60 mg/dL
Plasma creatinineaccepts 0.2–15 mg/dL
2 mg/dL

Results

Fractional excretion of sodium
0.476%
Interpretation
Below 1% — pattern of pre-renal azotaemia
Urine to plasma creatinine ratio
30.00

Step by step

  1. 1Values used
  2. 2Fractional excretion of sodium
  3. 3Fractional excretion of sodium= 0.476
  4. 4Interpretation= Below 1% — pattern of pre-renal azotaemia
  5. 5Urine to plasma creatinine ratio= 30.00

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.
  • This is an estimate for general information and not professional medical advice. See the full disclaimer for the limits that apply to this kind of calculator.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.

Frequently Asked Questions

When is FENa unreliable?

After diuretics, and in contrast nephropathy, glomerulonephritis or cirrhosis, where fractional excretion of urea is preferred.

What about FEUrea?

Fractional excretion of urea below 35% suggests a pre-renal state and is less affected by loop diuretics.

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