Fractional Excretion of Sodium (FENa) is a acute kidney injury tool commonly applied in Nephrology. FENa (%) = (urine Na × serum Cr) / (serum Na × urine Cr) × 100 using mEq/L for sodium and mg/dL for creatinine. Helps distinguish prerenal vs intrinsic AKI; confounded by diuretics, CKD, contrast, and other settings. Use the interactive calculator for inputs, limitations, and primary references.

Not a substitute for clinical judgment. Verify critical values with primary literature, local protocols, and specialist input when appropriate.