BUN Creatinine Ratio Calculator

What Is the BUN Creatinine Ratio?

The blood urea nitrogen (BUN) to creatinine ratio compares two kidney-related lab values. BUN reflects urea nitrogen from protein metabolism; creatinine reflects muscle breakdown filtered by the kidneys. Together they help distinguish prerenal from intrinsic renal causes of azotemia. For broader kidney assessment, use the GFR Calculator and BUN to Creatinine Ratio Calculator.

Formula

$$Ratio = \frac{BUN\ (mg/dL)}{Creatinine\ (mg/dL)}$$

Convert mmol/L creatinine to mg/dL by multiplying by 11.312. Convert BUN mmol/L to mg/dL by multiplying by 2.8.

Interpretation

Greater than 20:1 suggests prerenal azotemia (dehydration, heart failure, GI bleeding)
10 to 20:1: generally normal
Less than 10:1: may indicate intrinsic renal disease, liver disease, or malnutrition

Frequently Asked Questions

What is a normal BUN creatinine ratio?

Most references cite 10:1 to 20:1 as normal when both values are in mg/dL.

What does a ratio above 20 mean?

It often points to prerenal causes where BUN rises disproportionately to creatinine, such as dehydration or reduced kidney perfusion.

What does a ratio below 10 mean?

Low ratios may occur with intrinsic renal injury, advanced liver disease, low protein intake, or pregnancy.

Can I use mmol/L for creatinine?

Yes. Select mmol/L in the calculator and values are converted to mg/dL before the ratio is computed.

Does this replace GFR testing?

No. The ratio is one clue in acute settings. Estimated GFR provides a separate measure of chronic kidney function.

Report

BUN Creatinine Ratio Calculator

What Is the BUN Creatinine Ratio?

Formula

Interpretation

Frequently Asked Questions

Related Tools

Recent Visits