Fractional Excretion of Sodium

FENa = (UrineNa / SerumNa) / (UrineCr / SerumCr) * 100

Urine Na  
Serum Na  
Urine Cr  
Serum Cr  

Decimal Precision  
  • In this calculator, mcg is the abbreviation for micrograms.
  • The FENa helps differentiate acute tubular necrosis from a prerenal state.
  • FENa >2 % usually indicates ATN.
  • FENa <1% usually indicates a prerenal state such as dehydration or other forms of prerenal azotemia.
  • FENa's between 1% and 2% may be seen with either ATN or prerenal state.

  1. Stein JH, ed. Internal Medicine. 4th edition. Mosby-Year Book. 1994. NLMN ID: 9309759 NCBI Logo


Legal Notices and Disclaimer

All information contained in and produced by the EBMcalc system is provided for educational purposes only. This information should not be used for the diagnosis or treatment of any health problem or disease. THIS INFORMATION IS NOT INTENDED TO REPLACE CLINICAL JUDGMENT OR GUIDE INDIVIDUAL PATIENT CARE IN ANY MANNER. Click here for full notice and disclaimer.
EBMcalc is Copyright © 1998-2018 Foundation Internet Services    [Build 255633 v18.3]