Lab Values

Enter serum and urine sodium and creatinine values

For educational and clinical reference only. Not a substitute for professional medical judgment. Always correlate with clinical context. FENa is unreliable in patients on diuretics — use FEUrea instead.

Serum Values

Serum Sodium (mEq/L)

Normal: 136–145 mEq/L

Serum Creatinine (mg/dL)

Normal: 0.6–1.2 mg/dL (men)

Urine Values

Urine Sodium (mEq/L)

Pre-renal: <20; Intrinsic: >40

Urine Creatinine (mg/dL)

Typically 40–300 mg/dL

FEUrea (for diuretic patients) — Optional

Serum BUN (mg/dL)

Urine Urea (mg/dL)

Clinical Context

Diuretic Use?

AKI Stage (optional)

FENa Reference Values

Pre-renal AKI

FENa < 1%

Intrinsic AKI (ATN)

FENa > 2%

Gray zone

FENa 1–2%

FEUrea pre-renal

< 35%

FEUrea intrinsic

> 50%

Use FEUrea when

On diuretics

FENa Result

--%

fractional excretion of Na⁺

Interpretation

—

FEUrea

—

if urea values entered

Urine Na / Cr Ratio

—

spot urine sodium index

Limitations of FENa

Unreliable on diureticsUse FEUrea

Contrast nephropathyCan be <1%

MyoglobinuriaCan be <1%

CKD baselineAlters threshold

FENa Calculator

Lab Values

Calculation Breakdown

Clinical Interpretation

FENa Reference Values