Work out fractional excretion of sodium instantly with clear inputs, formula shown and shareable results.
Compares sodium clearance with creatinine clearance to judge whether the kidney is conserving sodium, the classic pre-renal versus intrinsic discriminator.
Fractional excretion of sodium
FENa (%) = (urine Na x plasma creatinine) / (plasma Na x urine creatinine) x 100
Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.
After diuretics, and in contrast nephropathy, glomerulonephritis or cirrhosis, where fractional excretion of urea is preferred.
Fractional excretion of urea below 35% suggests a pre-renal state and is less affected by loop diuretics.