FENa Calculator
Fractional Excretion of Sodium
Fractional Analyst
Enter paired plasma and urine chemistries to determine renal etiology.
Verified
Last Review: 2026-07-17
| < 1% | Prerenal Azotemia |
| 1% – 2% | Indeterminate / Mixed Etiology |
| > 2% | Acute Tubular Necrosis (ATN) |
Espinel CH. • JAMA. 1976;236(5):579-81. Established the 1% threshold as a discriminator between prerenal and intrinsic states.
Carvounis CP et al. • Kidney Int.. 2002;62(6):2223-9. Demonstrated the superiority of FEUrea over FENa in the setting of diuretics.
Last Comprehensive Review: 2026-07-17
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