BUN Creatinine Ratio Calculator

Counts the ratio of blood urea nitrogen to creatinine to differentiate between causes of acute renal failure.

Refer to the text below the tool for more information about the parameters involved and the interpretation of the ratio.

The BUN Creatinine Ratio is one of the kidney function indicators most often determined, especially if needed to determine the exact cause of renal malfunction.

Urea is a waste product of protein metabolization, formed in the liver and serves to measure state of nutrition, as well as liver and kidney function. Creatinine is a product of creatinine phosphate breakdown in muscles and usually depends on muscular mass, hence why men tend to have higher Cr values than women.

Both a high and low BUN Creatinine Ratio may be indicative of an impaired glomerular filtration rate, whether due to small flow or other issues with filtration.

BUN Creatinine Ratio = BUN / Creatinine

Interpretation:

>20: indicates pre-renal cause of ARF;
10-20: is a normal value or indicates post-renal cause;
<10: indicates renal cause of ARF.

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Steps on how to print your input & results:

1. Fill in the calculator/tool with your values and/or your answer choices and press Calculate.

2. Then you can click on the Print button to open a PDF in a separate window with the inputs and results. You can further save the PDF or print it.

Please note that once you have closed the PDF you need to click on the Calculate button before you try opening it again, otherwise the input and/or results may not appear in the pdf.

BUN Creatinine Ratio Explained

The BUN Creatinine Ratio is one of the kidney function indicators most often determined, especially if needed to determine the exact cause of renal malfunction.

Blood urea nitrogen and creatinine are two metabolites constantly produced by the body but whilst the BUN is filtered in the nephrons, in the kidney, then reabsorbed in the blood, creatinine is filtered then secreted in the lumen. Therefore, a healthy person naturally has more BUN in the blood than creatinine. If significant liver damage or disease inhibits the formation of urea, then BUN levels may fall.

BUN Creatinine Ratio = BUN / Creatinine

BUN and creatinine are measured in serum, usually in mg/dL. Reference range for the two parameters is summarized below:

Parameter	US units	SI units
Blood Urea Nitrogen (BUN)	7 – 30 mg/dL	2.5 – 10.7 mmol/L
Creatinine	0.7 – 1.2 mg/dL	62 – 106 µmol/L

Both a high and low BUN Creatinine Ratio may be indicative of an impaired glomerular filtration rate, whether due to small flow or other issues with filtration.

BUN Creatinine ratio interpretation

>20: indicates pre-renal cause of ARF;
10-20: is a normal value or indicates post-renal cause;
<10: indicates renal cause of ARF.

Potential causes of high and low BUN Creatinine ratios

BUN/Creatinine >20	BUN/Creatinine <10
Dehydration	Malnutrition
Hypovolemia	Pregnancy
High protein intake	Acute tubular necrosis
Shock	Liver disease
Congestive heart failure	SIADH (syndrome of inappropriate antidiuretic hormone)
Heart attack	Rhabdomyolysis
Gastrointestinal bleeding	-

References

Morgan DB, Carver ME, Payne RB. Plasma creatinine and urea: creatinine ratio in patients with raised plasma urea. Br Med J. 1977; 2(6092):929-32.

Witting MD, Magder L, Heins AE, Mattu A, Granja CA, Baumgarten M. ED predictors of upper gastrointestinal tract bleeding in patients without hematemesis. Am J Emerg Med. 2006; 24(3):280-5.

Feinfeld DA, Bargouthi H, Niaz Q, Carvounis CP. Massive and disproportionate elevation of blood urea nitrogen in acute azotemia. Int Urol Nephrol. 2002; 34(1):143-5.

Specialty: Nephrology

System: Urinary

Article By: Denise Nedea

Published On: June 16, 2020 · 12:00 AM

Last Checked: June 16, 2020

Next Review: June 16, 2025