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FEUrea Calculation: Understanding and Interpreting the Ratio

The Fractional Excretion of Urea (FEUrea) shows the ratio of urea in blood to urea in urine. An imbalance indicates two forms of Acute Renal Failure. A low ratio (less than 35 percent) indicates prerenal azotemia, while a high ratio (greater than 50 percent) indicates acute tubular necrosis (ATN).

Things You'll Need

  • Blood work analysis
  • Urinalysis
  • A calculator or a FEUrea app for smart phone
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Instructions

  1. Calculating FEUrea

    • 1

      Get a lab to do blood analysis and urinalysis on blood and urine samples.

    • 2

      Get the following data from the blood work and urinalysis: blood urea, urine urea, blood creatinine and urine creatinine.

    • 3

      Enter the data into the following formula (or enter into an online calculator or smart phone app): (urine urea / blood urea) / (urine creatinine/blood creatinine) * 100

    • 4

      If the resulting percentage is less than 35 percent, this indicates prerenal azotemia. If it is greater than 50 percent, this indicates acute tubular necrosis (ATN).

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