FENa Calculator (Fractional Excretion of Sodium)
Calculate fractional excretion of sodium with creatinine unit conversion.
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FENa
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Converted urine creatinine
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Converted serum creatinine
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About
Fractional excretion of sodium (FENa) compares urinary sodium excretion with filtered sodium using paired urine and serum sodium and creatinine measurements. Creatinine values are normalized before calculation, including mixed conventional and SI units. FENa is contextual laboratory arithmetic, not a stand-alone diagnosis of an acute kidney injury cause.
Formula
Interpretation
Units: Sodium must use the same numeric mmol/L or mEq/L system in serum and urine. Urine and serum creatinine may use different supported units because both are converted first.
Worked example: Urine sodium 20, serum sodium 140, urine creatinine 100 mg/dL, and serum creatinine 2 mg/dL gives FENa 0.286%.
Limitations: Diuretics, CKD, obstruction, glomerular disease, contrast exposure, and other settings can change interpretation. Use contemporaneous samples and clinical context; this page does not label results as prerenal or intrinsic AKI.
FAQ
Disclaimer
Educational and informational reference only. Not intended to replace professional medical advice, diagnosis, treatment, or independent verification.