BUN Creatinine Ratio Chart: Ranges, Causes and Next Steps

A typical adult BUN creatinine ratio is approximately 10:1 to 20:1, but the result cannot diagnose dehydration, kidney disease, or internal bleeding by itself. A BUN creatinine ratio chart can help you understand whether your result is below, within, or above the commonly used range, but the individual BUN and creatinine values are usually more important than the ratio alone.

Your healthcare professional may also review your estimated glomerular filtration rate, or eGFR, urine albumin, symptoms, medicines, fluid intake, diet, and previous laboratory results. Always use the reference range printed on your own report because ranges and testing methods can differ among laboratories.

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BUN Creatinine Ratio Chart

The following chart provides general adult reference points. It should be used for education rather than self-diagnosis.

BUN Creatinine Ratio	General Interpretation	Possible Explanations
Below 10:1	Lower than the commonly cited range	Low protein intake, malnutrition, overhydration, reduced urea production from significant liver disease, intense exercise, muscle injury, or creatinine rising more than BUN
10:1 to 20:1	Commonly cited adult range	Often considered an expected ratio, although BUN or creatinine may still be abnormal individually
Above 20:1	Higher than the commonly cited range	Dehydration, vomiting, diarrhea, reduced kidney blood flow, gastrointestinal bleeding, high protein intake, certain medicines, increased protein breakdown, urinary obstruction, or low muscle mass
Above 30:1	Markedly elevated	May occur with significant dehydration or upper gastrointestinal bleeding, but the ratio cannot confirm either condition

The University of Rochester Medical Center lists approximately 10:1 to 20:1 as a commonly used BUN-to-creatinine ratio range.

A number outside this interval does not automatically mean that something serious is wrong. It is a clue that should be interpreted alongside the rest of the blood test and your overall health.

What Is the BUN Creatinine Ratio?

The BUN creatinine ratio compares the amount of blood urea nitrogen with the amount of creatinine in your blood.

What Is BUN?

BUN stands for blood urea nitrogen. Urea is a waste product formed when the body breaks down protein.

The liver produces urea, which travels through the bloodstream to the kidneys. The kidneys normally filter it from the blood and remove it through urine.

BUN can be affected by:

Kidney filtration
Fluid intake and dehydration
Dietary protein
Gastrointestinal bleeding
Liver function
Infection, fever, burns, or trauma
Certain medicines

Because many factors influence BUN, an abnormal result does not always indicate a kidney problem.

What Is Creatinine?

Creatinine is a waste product produced during normal muscle metabolism. Healthy kidneys filter most creatinine from the blood.

Creatinine levels can be influenced by:

Kidney function
Muscle mass
Age
Body size
Physical activity
Recent intense exercise
Meat consumption
Some medicines and supplements

A muscular person may naturally have a higher creatinine level than someone with less muscle mass. Older adults or people with low muscle mass may have relatively low creatinine even when kidney function is reduced.

How to Calculate the BUN Creatinine Ratio

When both values are reported in milligrams per deciliter, or mg/dL, the calculation is:

BUN creatinine ratio = BUN ÷ creatinine

Example

Suppose your results are:

BUN: 18 mg/dL
Creatinine: 0.9 mg/dL

Calculation:

18 ÷ 0.9 = 20

The BUN creatinine ratio is therefore 20:1.

Important Note About Measurement Units

The 10:1 to 20:1 reference range is generally used when both BUN and creatinine are reported in mg/dL.

Some countries report:

Urea in mmol/L
Creatinine in µmol/L

You should not directly divide values reported in different units and compare the answer with the US ratio range. Use the ratio calculated by the laboratory or ask a healthcare professional to interpret the values.

What Is a Normal BUN Creatinine Ratio?

A ratio between approximately 10:1 and 20:1 is commonly considered within the expected adult range.

However, a normal ratio does not necessarily mean that both blood test values are normal.

For example:

BUN	Creatinine	Ratio	Interpretation
16 mg/dL	0.8 mg/dL	20:1	Ratio and individual values may be within range
40 mg/dL	2.0 mg/dL	20:1	Ratio is within the common range, but both values are elevated
8 mg/dL	0.8 mg/dL	10:1	Ratio may be normal, but the BUN is near the lower end
24 mg/dL	0.8 mg/dL	30:1	High ratio caused mainly by increased BUN

This is why the BUN creatinine ratio should never be interpreted without checking the individual results.

Typical BUN and Creatinine Reference Ranges

Reference ranges differ by laboratory, age, sex, muscle mass, pregnancy status, and testing method.

Examples published by the Cleveland Clinic include:

Blood Test	Example Adult Reference Range
BUN for females	6–21 mg/dL
BUN for males	8–24 mg/dL
Creatinine for women	Approximately 0.5–0.95 mg/dL
Creatinine for men	Approximately 0.7–1.3 mg/dL

These are general examples, not universal cutoffs. Use the reference range shown beside your result.

What Does a High BUN Creatinine Ratio Mean?

A BUN creatinine ratio above approximately 20:1 means that BUN is relatively high compared with creatinine.

This can happen because:

BUN has increased
Creatinine has decreased
Both changes are occurring at the same time

Dehydration or Fluid Loss

Dehydration is one of the most commonly discussed causes of a high ratio.

Possible reasons include:

Not drinking enough fluid
Heavy sweating
Vomiting
Diarrhea
Fever
Diuretic medicines
Significant blood loss

When blood volume decreases, the kidneys may reabsorb more urea, causing BUN to rise more than creatinine.

However, a high ratio does not confirm dehydration. Your symptoms, blood pressure, urine output, sodium level, and physical examination may also need to be considered.

Reduced Blood Flow to the Kidneys

Conditions that reduce kidney blood flow may increase BUN more than creatinine.

Possible examples include:

Heart failure
Severe dehydration
Major blood loss
Shock
Serious infection
Reduced circulating blood volume

These situations can range from mild to urgent, depending on the cause and accompanying symptoms.

Gastrointestinal Bleeding

Bleeding in the stomach or upper small intestine may increase BUN because digested blood acts as an additional protein source.

Possible warning signs include:

Black, sticky, tar-like stool
Vomiting blood
Vomit that resembles coffee grounds
Dizziness
Weakness
Fainting
Rapid heartbeat

A ratio above 30:1 may occur with upper gastrointestinal bleeding, but it is not specific enough to diagnose bleeding. The Mayo Clin i c advises seeking immediate medical care for significant gastrointestinal bleeding symptoms.

High Protein Intake

A high-protein meal or consistently high protein intake may increase urea production and raise BUN.

This effect may be more noticeable in people who:

Eat large amounts of meat
Use high-protein meal plans
Have reduced kidney function
Are dehydrated at the time of testing

A single result should be interpreted in context rather than used to make major dietary changes.

Increased Protein Breakdown

Illness or physical stress can increase the breakdown of body proteins.

Possible situations include:

Fever
Severe infection
Burns
Major surgery
Trauma
Prolonged corticosteroid use

This may raise BUN without causing an equivalent increase in creatinine.

Low Creatinine From Low Muscle Mass

A high ratio is not always caused by high BUN. It can also occur when creatinine is unusually low.

Low creatinine may be associated with:

Older age
Low muscle mass
Frailty
Prolonged illness
Malnutrition
Limb loss
Certain muscle conditions

For example, a BUN of 18 mg/dL and creatinine of 0.6 mg/dL produces a ratio of 30:1, even though the BUN itself may not be high.

Urinary Tract Obstruction

A blockage that interferes with urine flow may affect BUN, creatinine, or both.

Possible causes include:

Kidney stones
Enlarged prostate
Urinary tract narrowing
Blood clots
Bladder retention
Tumors pressing on the urinary tract

A person with sudden inability to urinate, severe pain, or sharply reduced urine output needs prompt medical evaluation.

What Does a Low BUN Creatinine Ratio Mean?

A ratio below approximately 10:1 means BUN is relatively low compared with creatinine.

The cause may be related to low BUN, increased creatinine, or both.

Low Protein Intake

Because urea is produced from protein breakdown, a low-protein diet may reduce BUN.

This may occur in people who:

Follow a highly restricted diet
Have difficulty eating
Have swallowing problems
Experience prolonged nausea
Have poor access to adequate nutrition

A low result alone does not prove protein deficiency.

Malnutrition

Inadequate calorie and protein intake may lower urea production. Malnutrition may also reduce muscle mass, making interpretation more complicated.

Possible accompanying signs include:

Unintentional weight loss
Weakness
Fatigue
Muscle loss
Poor appetite

Overhydration

Drinking a very large amount of fluid or retaining excess water may dilute BUN.

Overhydration may occur because of:

Excessive fluid intake
Intravenous fluids
Certain hormonal conditions
Heart, liver, or kidney problems that affect fluid balance

People with kidney disease, heart failure, or liver disease should not increase fluid intake solely to change a laboratory result unless advised by a healthcare professional.

Reduced Urea Production From Liver Disease

The liver converts waste nitrogen into urea. Significant liver dysfunction may therefore lower BUN.

A low ratio alone cannot diagnose liver disease. Other information may include:

Liver enzyme results
Bilirubin
Albumin
Blood-clotting tests
Imaging
Symptoms such as jaundice or abdominal swelling

Increased Creatinine

The ratio may decrease when creatinine rises more than BUN.

Possible reasons include:

Acute kidney injury
Some forms of intrinsic kidney damage
Muscle injury
Rhabdomyolysis
Intense exercise
Recent cooked meat intake
Certain medicines

Traditional medical teaching sometimes links a low ratio with intrinsic kidney injury. However, the ratio is not reliable enough to determine the type of kidney injury on its own.

Does a High Ratio Always Mean Kidney Disease?

No. A high BUN creatinine ratio does not automatically mean kidney disease.

BUN can increase because of dehydration, gastrointestinal bleeding, protein intake, illness, or medicines. Creatinine can remain normal or become low because of limited muscle mass.

Likewise, a person can have kidney disease while the ratio remains between 10:1 and 20:1.

Kidney function is usually evaluated using more informative measurements, including:

Serum creatinine
eGFR
Urine albumin-to-creatinine ratio
Urinalysis
Changes over time
Blood pressure
Medical history

The National Institute of Diabetes and Digestive and Kidney Diseases identifies eGFR and urine albumin testing as important tools for detecting and monitoring chronic kidney disease.

BUN Creatinine Ratio vs. Urine Albumin Creatinine Ratio

These tests sound similar but measure different things.

Test	Sample	What It Measures	Main Use
BUN creatinine ratio	Blood	BUN compared with creatinine	Provides general context about the relationship between two waste products
Urine albumin-to-creatinine ratio, or UACR	Urine	Albumin compared with urine creatinine	Helps detect kidney damage and abnormal protein leakage
eGFR	Calculated from blood creatinine and other information	Estimated kidney filtration	Helps assess overall kidney filtering function

The BUN creatinine ratio should not be used as a substitute for eGFR or urine albumin testing.

Factors That Can Affect Your Test Results

Before interpreting an unusual ratio, consider what happened during the hours or days before the blood draw.

Diet

Possible influences include:

A large meat meal
High protein intake
Very low protein intake
Poor food intake
Fasting

Fluid Balance

Results may change with:

Dehydration
Vomiting
Diarrhea
Heavy exercise
Excessive fluid intake
Diuretic use

Exercise

Intense exercise may temporarily increase creatinine. Severe muscle injury may cause a much larger increase and requires medical evaluation.

Medicines and Supplements

Medicines that may affect BUN, creatinine, kidney blood flow, or kidney function include:

Diuretics
Corticosteroids
Some antibiotics
Nonsteroidal anti-inflammatory drugs
Certain blood pressure medicines
Creatine supplements
Some chemotherapy medicines

Do not stop a prescription medicine because of a laboratory result without speaking with the prescriber.

Age and Muscle Mass

Creatinine may be lower in older adults and people with low muscle mass. This can make the ratio appear high even when BUN is not significantly elevated.

Pregnancy

Pregnancy can change kidney filtration and fluid balance. Pregnant patients should use pregnancy-specific medical interpretation rather than relying only on a general adult ratio chart.

What to Do After an Abnormal BUN Creatinine Ratio

An isolated abnormal ratio is not usually enough to identify the cause. The following steps can help you discuss the result with a healthcare professional.

1. Check the Actual BUN and Creatinine Values

Determine whether:

Only BUN is abnormal
Only creatinine is abnormal
Both are abnormal
Both are technically within range

The same ratio can result from very different combinations.

2. Confirm the Units and Laboratory Range

Check whether the values are reported in mg/dL or SI units.

Use the reference intervals printed on the report rather than relying only on a general online chart.

3. Review Your eGFR

eGFR estimates how well the kidneys are filtering blood.

A single low eGFR does not always confirm chronic kidney disease. According to the 2024 KDIGO chronic kidney disease guideline, unexpected abnormalities may need repeat testing and evaluation for chronicity.

4. Review Urine Testing

A clinician may recommend:

Urinalysis
Urine albumin-to-creatinine ratio
Urine protein testing
Urine microscopy

These tests can identify blood, protein, infection, or other clues that a blood ratio cannot show.

5. Compare With Previous Results

A stable ratio that has remained similar for years may mean something different from a sudden change.

Bring previous laboratory reports to your appointment when possible.

6. Consider Recent Symptoms and Activities

Tell your healthcare professional about:

Vomiting or diarrhea
Fever
Reduced fluid intake
Heavy exercise
High-protein meals
New medicines
Supplements
Urinary changes
Black or bloody stool
Unintentional weight loss

7. Follow Recommendations for Repeat Testing

A clinician may repeat the test after correcting a temporary factor such as dehydration or after reviewing medicines.

Do not try to force the result into the normal range by rapidly drinking large amounts of water or severely restricting protein.

When to Seek Urgent Medical Care

The ratio alone rarely determines whether emergency care is needed. Symptoms are more important.

Seek urgent medical evaluation for:

Black, sticky, tar-like stool
Vomiting blood
Coffee-ground-like vomit
Heavy rectal bleeding
Fainting or severe dizziness
Rapid heartbeat with weakness
Little or no urine
Sudden inability to urinate
Severe shortness of breath
New confusion
Severe abdominal, back, or side pain
Rapidly worsening swelling
Signs of severe dehydration

Call emergency services for severe bleeding, loss of consciousness, breathing difficulty, or signs of shock.

Frequently Asked Questions

Is a BUN creatinine ratio of 25 high?

A ratio of 25:1 is above the commonly cited adult range of 10:1 to 20:1. It may occur with dehydration, gastrointestinal bleeding, increased protein breakdown, high protein intake, or low creatinine caused by low muscle mass.

The individual BUN and creatinine values are needed to interpret it correctly.

Is a BUN creatinine ratio of 30 dangerous?

A ratio of 30:1 is elevated, but the number alone does not show how serious the situation is.

For example, it may result from mild dehydration or a low creatinine level. It may also occur with more serious problems such as significant fluid loss or gastrointestinal bleeding.

Urgency depends on symptoms, the individual blood values, eGFR, medical history, and the cause.

Can dehydration cause a high BUN creatinine ratio?

Yes. Dehydration can reduce circulating blood volume and increase urea reabsorption, causing BUN to rise more than creatinine.

However, the ratio cannot confirm dehydration without additional information.

Can the ratio be normal when kidney function is abnormal?

Yes. BUN and creatinine can rise together while maintaining a ratio between 10:1 and 20:1.

A normal ratio therefore does not rule out acute kidney injury or chronic kidney disease.

What foods can raise the BUN creatinine ratio?

A large amount of protein, particularly meat, may temporarily increase BUN. Gastrointestinal bleeding can also raise BUN because digested blood functions as a protein source.

Diet is only one possible influence and should not be assumed to be the cause without reviewing the complete result.

Does a low BUN creatinine ratio mean liver disease?

Not necessarily. Significant liver dysfunction can reduce urea production and lower BUN, but other causes include low protein intake, overhydration, malnutrition, exercise, muscle injury, or elevated creatinine.

Additional liver tests and clinical evaluation would be needed.

Should I drink more water if my ratio is high?

Not automatically. Drinking normal amounts may be reasonable when mild dehydration is likely and you do not have a fluid restriction.

However, excessive water intake can be harmful. People with kidney disease, heart failure, liver disease, low sodium, or prescribed fluid limits should speak with a healthcare professional before changing fluid intake.

Conclusion

A BUN creatinine ratio chart can help place your result into a general range, but it cannot identify the cause by itself. Approximately 10:1 to 20:1 is commonly used as an adult reference, while values above or below that interval require interpretation of the separate BUN and creatinine levels.

Review the laboratory range, eGFR, urine tests, symptoms, medicines, hydration status, diet, and previous results. Contact a healthcare professional if the result is unexplained, repeatedly abnormal, or accompanied by urinary changes, weakness, swelling, vomiting, diarrhea, or possible bleeding.

This content is for informational purposes only and not medical advice.