BUN/Creatinine Ratio Calculator

Author: Henrick Yau
- 10 October 2026
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Calculators

The BUN to Creatinine ratio is an important diagnostic tool that helps assess kidney function and identify various medical conditions. This calculator determines your BUN to Creatinine ratio and provides information about what your results might indicate.

Test Results

Normal range: 7-20 mg/dL or 2.5-7.1 mmol/L
Normal range: 0.7-1.3 mg/dL or 62-115 µmol/L

Patient Information

Additional Factors

Understanding the BUN to Creatinine Ratio

The BUN to Creatinine ratio compares two important kidney function markers: Blood Urea Nitrogen (BUN) and Creatinine. This ratio can help healthcare providers distinguish between different causes of kidney dysfunction and other medical conditions.

What the Ratio Indicates
  • Normal ratio (10-20:1): Typically indicates normal kidney function
  • Elevated ratio (>20:1): May suggest pre-renal causes (dehydration, heart failure, gastrointestinal bleeding)
  • Low ratio (<10:1): May indicate intrinsic renal disease, malnutrition, or low protein intake
Factors Affecting BUN Levels
  • Increased BUN: Dehydration, high protein diet, gastrointestinal bleeding, certain medications, heart failure, urinary tract obstruction
  • Decreased BUN: Overhydration, malnutrition, severe liver disease, low protein diet
Factors Affecting Creatinine Levels
  • Increased Creatinine: Kidney disease or damage, certain medications, muscle breakdown, dehydration
  • Decreased Creatinine: Muscle wasting, advanced age, liver disease
Important Considerations
  • The ratio should always be interpreted alongside absolute BUN and creatinine values
  • Age, sex, muscle mass, and diet can all affect normal values
  • This ratio is one of many tools used to assess kidney function and should not be used in isolation
  • Always consult with a healthcare provider for proper interpretation of lab results

Disclaimer: This calculator provides estimates based on general guidelines and is for educational purposes only. It is not intended to replace professional medical advice, diagnosis, or treatment. Always consult with a qualified healthcare provider regarding your specific medical condition and before making any healthcare decisions.

BUN:Creatinine Ratio Formula:
\( \text{Ratio} = \frac{\text{BUN (mg/dL)}}{\text{Creatinine (mg/dL)}} \)

What Is the BUN:Creatinine Ratio Calculator?

The BUN:Creatinine Ratio Calculator is a straightforward, interactive tool designed to estimate the ratio between two key blood markers: Blood Urea Nitrogen (BUN) and Creatinine. This ratio can offer valuable insight into kidney function and overall hydration status.

Whether you're reviewing your lab results or managing a medical condition, this calculator helps you determine if your ratio falls within the expected range or if it points to a potential health concern.

Why the BUN-to-creatinine ratio matters

BUN and Creatinine are waste products that your kidneys filter out. By comparing their levels, healthcare professionals can gain a clearer picture of what's happening in your body. This ratio is particularly useful for distinguishing between:

  • Dehydration and kidney disease
  • Pre-renal and renal causes of dysfunction
  • Normal kidney function versus possible malnutrition or liver issues

Entering your BUN and creatinine values

For the most accurate results, follow these steps:

  • Enter your BUN value and select the correct unit (mg/dL or mmol/L).
  • Input your Creatinine value and select the unit (mg/dL or µmol/L).
  • Fill in patient details such as age, sex, hydration status, and any relevant medications.
  • Optional: Check any additional health factors that may influence the result, like recent illness or diet.
  • Click “Calculate BUN:Creatinine Ratio” to see your results and interpretation.

What Your Results Mean

The tool categorises the ratio into one of four ranges—Low, Normal, High, or Very High—each offering insight into possible causes and next steps.

  • 10–20:1 (Normal): Typically reflects healthy kidney function.
  • Greater than 20:1 (High): May suggest dehydration, heart issues, or gastrointestinal bleeding.
  • Less than 10:1 (Low): Might point to intrinsic kidney problems, malnutrition, or liver conditions.

You'll also receive a breakdown of contributing factors and practical recommendations, such as hydration tips or when to seek further medical advice.

Who should monitor this ratio

This calculator is useful for anyone monitoring their kidney function, whether due to chronic conditions or recent lab tests. It is especially relevant for:

  • Patients managing kidney disease or diabetes
  • Individuals experiencing dehydration or fluid imbalance
  • Those on medications affecting kidney function (e.g., NSAIDs, diuretics)

Questions about the BUN:creatinine ratio

Is this calculator a replacement for medical advice?

No. The tool is for informational purposes only. Always consult your healthcare provider for diagnosis and treatment.

Do I need to convert my units?

No. The calculator accepts both U.S. and international units for BUN and Creatinine. It automatically converts values for accurate results.

How accurate is the interpretation?

The calculator uses recognised clinical ranges and conditions. While it offers reliable estimates, medical interpretation should include other lab results and symptoms.

Can hydration or diet affect the results?

Yes. Factors like high protein intake, recent illness, or dehydration can impact BUN and Creatinine levels. The calculator accounts for these through additional input fields.

Additional Tools You Might Find Useful

If you're using this calculator, you may also be interested in:

  • GFR Calculator: For a deeper look at kidney filtering function (eGFR calculation).
  • Corrected Calcium Calculator: To assess serum calcium adjustments in various conditions.
  • BAC Estimator: To track blood alcohol levels and manage alcohol consumption responsibly.
  • Body Type Assessment: Understand your body shape and physical characteristics.
  • Oxfam Care Planning Tool: For those considering philanthropy and social care contributions.

Using the ratio to understand kidney health

The BUN:Creatinine Ratio Calculator is a practical, easy-to-use tool for understanding an important aspect of your kidney health. It simplifies a key medical calculation and provides clear, actionable insights to guide your next steps. If you have concerns about your results, speak with a healthcare provider for personalised evaluation.