Renal & Electrolytes

Fractional Excretion of Urea (FEUrea) Calculator

Urea-based fractional excretion that helps separate prerenal from intrinsic kidney injury when diuretics make FENa unreliable.

Reviewed by Alex G, BSN, RN, CEN, CCRN, CMC, NREMT-P · From the Reference tab of the app

Turn on JavaScript to use this calculator, or open it in the web app.

Formula

((Urine Urea * Serum Cr) / (Serum BUN * Urine Cr)) * 100

How it is used

• FEUrea is used to differentiate pre-renal vs intrinsic AKI, especially in patients receiving diuretics (where FENa is inaccurate).

• < 35%: Suggests pre-renal AKI (kidneys are holding onto urea and water).
• > 50%: Suggests intrinsic AKI (ATN - tubules are damaged and spilling urea).

Same formula as the app. Open it in the web app.

Related one-pagers

• Acute Kidney InjuryFEUrea (on diuretics) · <35% · >50%
• Electrolyte Imbalances
• ABG Interpretation in 6 Steps
• CRRT (Continuous Renal Replacement)

Related calculators

• Anion Gap
• BUN/Cr Ratio
• Corrected Calcium
• Corrected Sodium (Hyperglycemia)
• Creatinine Clearance (Cockcroft-Gault)
• CRRT Effluent Dose (mL/kg/h)
• Fractional Excretion of Sodium (FENa)
• Free Water Deficit

For education and exam preparation only. Follow your institution’s protocols. For education and exam preparation only. Verify results independently and follow your institution’s protocols. Not a substitute for clinical judgment.