BUN Creatinine Ratio Calculator

This is an online BUN creatinine ratio calculator that helps you calculate the BUN to Creatinine Ratio (BUN:Cr). Carry on reading to find out how to calculate the BUN creatinine ratio and what does it mean if the BUN creatinine ratio is high or low.

What is BUN to creatinine ratio?

The BUN to creatinine ratio is the ratio of the blood urea nitrogen (BUN) (mg/dL) and serum creatinine (Cr) (mg/dL). The ratio can be used to determine the cause of acute kidney injury.

The formula for calculating BUN to creatinine ratio

The BUN to creatinine ratio calculation formula is as follows:

BUN to Creatinine Ratio = Blood urea nitrogen / Serum creatinine

Interpreting BUN creatinine ratio

You may wonder what does it mean if someone’s BUN creatinine ratio is too high or low. Here is a classification:

  • BUN/creatinine ratio >20 suggests a prerenal cause
  • BUN/creatinine ratio <10 suggests an intrinsic renal cause

What causes BUN to creatinine ratio too high or too low? we’ve summarized the possible causes below.

BUN/creatinine greater than 20 BUN/creatinine below 10
  • Advanced age
  • Congestive heart failure
  • Corticosteroids administration or Cushing’s syndrome
  • Dehydration
  • Gastrointestinal bleeding
  • Hypovolemia
  • Shock, heart attack, severe burns
  • Very high protein intake
  • Acute tubular necrosis
  • Liver disease
  • Malnutrition
  • Pregnancy
  • Rhabdomyolysis
  • SIADH (syndrome of inappropriate antidiuretic hormone)
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