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BUN Creatinine Ratio Calculator

BUN creatinine ratio calculator determines the ratio of blood urea nitrogen to serum creatinine. Normal ratio is 10:1 to 20:1, with values above 20:1 suggesting prerenal azotemia and below 10:1 suggesting liver disease or malnutrition.

Enter Values

BUN (mg/dL)

Serum Creatinine (mg/dL)

Result

Enter values above and click Calculate to see your result.

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Formula

Core Formula

\text{Ratio} = \frac{\text{BUN}}{\text{Serum Creatinine}}

How it works: A high ratio (>20:1) suggests a pre-renal cause, while a lower ratio (<10:1) may suggest intrinsic renal damage.

Worked Example

BUN 40, Creatinine 1.0 -> Ratio 40.

Understanding the BUN to Creatinine Ratio

The BUN/Creatinine ratio helps clinicians determine the underlying cause of elevated kidney markers by comparing how BUN and creatinine change relative to each other in different conditions.

Normal ratio: 10:1 to 20:1 (BUN divided by serum creatinine)
Above 20:1 suggests prerenal causes such as dehydration, congestive heart failure, or GI bleeding
Below 10:1 suggests liver disease, malnutrition, or rhabdomyolysis
Normal BUN range: 7 to 20 mg/dL; normal creatinine: 0.7 to 1.3 mg/dL (men), 0.6 to 1.1 mg/dL (women)
Both values elevated with normal ratio suggests intrinsic renal disease or post-renal obstruction

This calculator is for educational purposes only. Clinical context, patient history, and additional laboratory tests are essential for accurate diagnosis of kidney injury.

You can also calculate changes using our eGFR Calculator (MDRD) or FeNa Calculator.

Frequently Asked Questions

What is a normal BUN/Creatinine ratio?

A normal ratio is typically between 10:1 and 20:1. Normal BUN is 7 to 20 mg/dL and normal creatinine is 0.7 to 1.3 mg/dL for men and 0.6 to 1.1 mg/dL for women.

What causes a ratio above 20:1?

A high ratio often indicates prerenal azotemia from dehydration, congestive heart failure, gastrointestinal bleeding, or a high-protein diet. BUN rises disproportionately because the kidneys reabsorb more urea when blood flow is reduced.

What does a ratio below 10:1 mean?

A low ratio may suggest liver disease (reduced urea production), malnutrition, or conditions that raise creatinine disproportionately, such as rhabdomyolysis.

What if both BUN and Creatinine are high?

When both values are elevated with a ratio in the normal 10:1 to 20:1 range, this usually indicates intrinsic kidney damage or post-renal obstruction.

Can medications affect the BUN/Creatinine ratio?

Yes. Steroids and tetracyclines can increase BUN without affecting creatinine, raising the ratio. Certain drugs like cimetidine can decrease creatinine secretion, also altering the ratio.

Is this calculator a substitute for medical advice?

No. This tool is for educational purposes only. Always consult a healthcare professional for proper evaluation of kidney function.

Is it possible to embed the BUN Creatinine Ratio Calculator on another website?

Yes, embedding the BUN Creatinine Ratio Calculator is free. Hit the "Embed" button on this page, adjust the width, height, and theme, then grab the iframe code. It works on WordPress, Wix, Squarespace, Shopify, and plain HTML pages. No registration needed. Full instructions at calculory.com/services/embed-calculators.

Medical Disclaimer

This calculator is provided for informational and educational purposes only. It is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making any decisions based on these results. Do not disregard or delay seeking medical advice because of information obtained from this tool.

AI Assistant

Ask about this calculator

I can help you understand the bun creatinine ratio calculator formula, interpret your results, and answer follow-up questions.

Try asking

Our AI assistant provides general estimates and advice only. Please consult a qualified healthcare professional before making any health-related decisions.

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eGFR Calculator (MDRD)FeNa Calculator

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