Fractional sodium excretion compares urine and serum sodium while accounting for urine concentration through creatinine.
Fractional Excretion of Sodium
Form
Results
FENa
0 %
Status
Table of Contents
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What is Fractional Excretion of Sodium?
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How to Use This Calculator
- Enter or select Serum sodium, Serum creatinine, Urine sodium, Urine creatinine.
- Check the unit beside each measurement. For a percentage or rate, use the scale and time period stated in the form.
- Choose Calculate, then compare the output with the formula and example below. If you change a value or option, calculate again to update the result.
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Formula Used
FENa (%) = urine sodium × serum creatinine/(serum sodium × urine creatinine) × 100
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Variables Explained
| Input | What it means |
|---|---|
| Serum sodium | Sodium concentration, normally in mmol/L or mEq/L; follow the form’s unit label. |
| Serum creatinine | The laboratory creatinine concentration; mg/dL and µmol/L need different numeric values. |
| Urine sodium | Sodium concentration, normally in mmol/L or mEq/L; follow the form’s unit label. |
| Urine creatinine | The laboratory creatinine concentration; mg/dL and µmol/L need different numeric values. |
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Worked Example
Urine sodium 20, serum creatinine 1, serum sodium 140 and urine creatinine 100 give FENa≈0.14%.
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Why Use This Calculator?
Use the calculation to make the method and its inputs easier to check with a healthcare professional. Its meaning depends on the clinical setting and on whether the underlying method is appropriate for that person.
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Common Mistakes
- Diuretics and several kidney conditions affect interpretation; the result cannot establish a cause on its own.
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Frequently Asked Questions
Is this result a diagnosis or treatment instruction?
No. It describes a calculation or score from the supplied information. A qualified clinician must check the measurements, the method’s applicability and the wider clinical picture.
Can I enter the units from any lab report?
Use the units specified in the form and select a conversion only where the page provides one. Different substances need different conversion factors; a mismatch can produce a plausible but incorrect result.
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Sources & References
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