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Fractional Excretion of Potassium

Aka: Fractional Excretion of Potassium, FEK

Indications
1. Hyperkalemia
Precautions
1. Results altered by Hyperkalemia Management
2. Obtain lab sample prior to intervention if possible
  1. Do not delay treatment in emergent Hyperkalemia
Labs
1. Serum Potassium and Serum Creatinine
2. Spot urine for Urine Potassium and Urine Creatinine
Formula
1. FEK = (Potassium Excretion x 100)/(total filtered load)
  1. Potassium (K+) Excretion = (Urine K+) / (Serum K+)
  2. Total Load = (Urine Creatinine) / (Serum Creatinine)
2. FEK = (uK x sCr x 100) / (sK x uCr)
Interpretation of Fractional Excretion of Potassium
1. FEK <10%: Renal cause of Hyperkalemia
2. FEK >10%: Extrarenal cause of Hyperkalemia
  1. May also be increased in Chronic Renal Failure

Family Practice Notebook

Patients should address specific medical concerns with their physicians.

Although access to this page is not restricted, the information found here is intended for use by medical providers.

This page was written by Scott Moses, MD, last revised on 10/21/2007 and last published on 6/18/2013.

This is one of 5909 pages in the Family Practice Notebook