Fractional Excretion of Sodium (FENa) Calculator
Calculate the fractional excretion of sodium to differentiate prerenal from intrinsic renal causes of acute kidney injury.
Medical Disclaimer
This calculator is for informational and educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making decisions about your health. Never disregard professional medical advice or delay seeking it because of results from this tool.
Inputs
FENa <1% (urine Na typically <20): prerenal azotemia; FENa >2% (urine Na >40): ATN/intrinsic renal disease
Normal Na: 136–145 mEq/L; hyponatremia <136; hypernatremia >145; critical <120 or >160 mEq/L
Results
FENa
0.21%
Classification
1(1=Prerenal, 2=Indeterminate, 3=Intrinsic)
How to Use This Calculator
- Enter urine sodium, plasma sodium, urine creatinine, and plasma creatinine (all in mEq/L or mg/dL).
- Review FENa (%) — < 1% suggests pre-renal azotemia; > 2% suggests intrinsic renal or post-renal cause.
- FENa is unreliable in patients on diuretics — use FEUrea in that setting.
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