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Fractional excretion of sodium (FENa) and urea (FEUrea)

Renal

Separates prerenal AKI from tubular injury. FEUrea is the one to use when the patient has had diuretics.

What you enter

  • Urine sodium (mmol/L)
  • Plasma sodium (mmol/L)
  • Urine creatinine (mg/dL or mmol/L or µmol/L)
  • Plasma creatinine (mg/dL or µmol/L)
  • Urine urea (optional) (mmol/L or mg/dL BUN)
  • Plasma urea (optional) (mmol/L or mg/dL BUN)
FORMULAFENa = (UNa × PCr) ÷ (PNa × UCr) × 100; FEUrea = (UUrea × PCr) ÷ (PUrea × UCr) × 100
SourceCarvounis CP et al. Significance of the fractional excretion of urea in the differential diagnosis of acute renal failure. Kidney Int 2002;62:2223-9ReviewedFormula and thresholds checked against the source on 2026-08-22. If the source updates, this line will say so.