Nephrology

Fractional Excretion of Sodium (FENa)

Distinguishes pre-renal from intrinsic AKI.

Education and reference only. Not a substitute for clinical judgement, local policy or product labelling. Always verify before clinical use. Values are calculated in your browser and never stored.

When to use

Use in acute kidney injury (in oliguria, before diuretics) to help distinguish pre-renal from intrinsic (e.g. ATN) causes.

Why use

It helps localise the cause of AKI when the picture is unclear.

Critical actions

Use consistent creatinine units (they cancel). Unreliable after diuretics or in CKD; FEUrea may be preferred if on diuretics.

Evidence & references

  1. Espinel CH. The FENa test. JAMA. 1976.

Related calculators

Creatinine Clearance (Cockcroft-Gault)Estimated creatinine clearance for drug dosing.eGFR (CKD-EPI 2021)Estimated GFR, race-free creatinine equation.

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