BUN Creatinine Ratio Calculator - BCR

BUN Creatinine Ratio Calculator - BCR

BUN Creatinine Ratio Calculator

BUN (Blood Urea Nitrogen) (mg/dL)
Serum Creatinine (mg/dL)

BUN Creatinine Ratio Calculator - Blood Urea Nitrogen

  • BUN Creatinine Ratio Calculator will count the ratio of a patient's blood urea nitrogen to their creatinine levels.
  • 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 and 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.


Steps To Calculate BUN/Creatinine Ratio

  1. Enter Blood Urea Nitrogen (BUN) Value
  2. Enter Serum Creatinine Value
  3. Check BUN Creatinine Ratio


BUN/Creatinine Ratio Calculator Formulas

  • BUN creatinine ratio = blood urea nitrogen (mg/dL) / serum creatinine (mg/dL)


  • BUN Creatinine Ratio = BUN / Creatinine


Reference Range for BUN/Creatinine Ratio

BUN and creatinine are measured in serum, usually in mg/dL.

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


Calculate BUN Creatinine

  • The blood urea nitrogen (BUN) test is valuable for determining if there is a problem with your kidneys or your nutrition.
  • But to deepen the diagnosis and try to find the exact cause of the renal malfunction, we perform a test called the BUN creatinine ratio.
  • It uses two values, both measured in serum – blood urea nitrogen and creatinine.
  • BUN and creatinine levels depend on kidney function but are bound together to give you a clue about the localization of the damage - whether it's an intrinsic renal or prerenal problem.
  • If you don’t know how to calculate the BUN creatinine ratio, you can use our BUN creatinine ratio.


BUN Creatinine Ratio Outcomes

The below table shows the list of possible causes for both outcomes – all should be considered:

BUN/creatinine >20 BUN/creatinine <10
Dehydration Acute tubular necrosis
Hypovolemia Liver disease
Shock, heart attack, severe burns Malnutrition
Congestive heart failure Pregnancy
Very high protein intake SIADH (syndrome of inappropriate antidiuretic hormone)
Gastrointestinal bleeding Rhabdomyolysis


BUN Creatinine Ratio Normal Range Table


BUN/Creatinine Ratio Low

A low BUN/Creatinine ratio usually indicates an underlying disease or disorder, often accompanied by specific symptoms related to that condition.

The following factors are commonly associated with a low BUN/creatinine ratio:

  • Low protein intake: Malnutrition or starvation can lead to decreased protein intake, resulting in lower BUN production and a reduced BUN/creatinine ratio.
  • Advanced liver disease: When the liver is unable to produce enough urea, typically seen in advanced liver disease, it can cause lower BUN levels and a decreased BUN/creatinine ratio.
  • Sickle cell anemia: In sickle cell anemia, the kidneys reabsorb less urea, leading to increased urinary loss and lower BUN levels, resulting in a reduced BUN/creatinine ratio.
  • Hypothyroidism: Insufficient production of thyroid hormones in hypothyroidism can increase creatinine levels, contributing to a lower BUN/creatinine ratio.
  • Rhabdomyolysis: Rhabdomyolysis occurs when damaged muscles break down rapidly, leading to elevated creatinine levels and a lower BUN/creatinine ratio.
  • Kidney damage and kidney failure: Impaired kidney function, regardless of the underlying cause, can result in increased creatinine levels, leading to a reduced BUN/creatinine ratio.
  • Medications: Certain medications, such as acetazolamide (a diuretic used for various conditions), can affect BUN and creatinine levels, potentially causing a lower BUN/creatinine ratio.

Low BUN/Creatinine ratio: Causes may include low protein intake, liver disease, sickle cell anemia, hypothyroidism, rhabdomyolysis, kidney damage, or certain medications. Consult a healthcare professional for accurate diagnosis.


BUN/Creatinine Ratio High

A high BUN/Creatinine ratio usually indicates an underlying disease or disorder, often accompanied by specific symptoms related to that condition.

The following factors are commonly associated with a high BUN/creatinine ratio:

  • Dehydration: When the body lacks sufficient fluids, both BUN and creatinine levels can increase. However, BUN levels tend to rise more significantly than creatinine levels in cases of dehydration.
  • Gastrointestinal bleeding: Blood loss in the gastrointestinal tract can lead to higher protein and BUN levels, consequently increasing the BUN/creatinine ratio.
  • Hyperthyroidism: An overactive thyroid gland (hyperthyroidism) can cause an elevation in BUN levels and a decrease in creatinine levels, resulting in a high BUN/creatinine ratio.
  • Congestive heart failure: Heart failure can affect kidney function, leading to increased reabsorption of urea and elevated BUN levels, thereby raising the BUN/creatinine ratio.
  • Kidney disease: Various kidney diseases or disorders can raise both BUN and creatinine levels, resulting in a high BUN/creatinine ratio.
  • Medications: Certain medications, such as tetracycline (an antibiotic) or corticosteroids (used for inflammation), can influence BUN and creatinine levels, potentially leading to an elevated BUN/creatinine ratio.

High BUN/Creatinine ratio: Dehydration, gut bleeding, hyperthyroidism, heart failure, kidney disease, or certain medications may be involved. Consult a healthcare professional for accurate diagnosis.


Blood Urea

  • A BUN, or blood urea nitrogen test, can provide important information about your kidney function.
  • The main job of your kidneys is to remove waste and extra fluid from your body.
  • If you have kidney disease, this waste material can build up in your blood.
  • Over time, this may lead to serious health problems, including high blood pressure, anemia, and heart disease.
  • The BUN test measures the amount of urea nitrogen in your blood.
  • Urea nitrogen is a waste product that your kidneys remove from your blood.
  • Higher than normal BUN levels may be a sign that your kidneys aren't working well.


Urea Nitrogen

  • The normal range of blood urea nitrogen is 8-20 mg/dL (2.9-7.1 mmol/L).
  • High values (>20 mg/dL) can be caused by: a diet rich in high protein foods (e.g., high meat intake), kidney malfunction, congestive heart failure, gastrointestinal hemorrhage, or states of increased catabolism (massive burns or cancer).
  • Low values (<8 mg/dL) can be caused by: malnutrition, liver disease, and SIADH (syndrome of inappropriate antidiuretic hormone).
  • Urea is a waste product of protein metabolization, formed in the liver, and serves to measure the state of nutrition, as well as liver and kidney function.



  • Creatinine is a chemical compound left over from energy-producing processes in your muscles.
  • Healthy kidneys filter creatinine out of the blood.
  • Creatinine exits your body as a waste product in urine.
  • Your doctor may also order a creatinine test, which is another blood test that also checks your kidney health.
  • This is because the BUN level by itself doesn’t always reveal much.
  • When your BUN levels are compared with your creatinine levels, it gives a fuller picture of what’s happening with your kidneys.
  • This is known as the BUN/Creatinine ratio.
  • Creatinine is a waste product from your muscles that is also filtered by your kidneys.
  • Like BUN, high levels of creatinine could mean there is a lot of waste product that hasn’t been removed by the kidneys.
  • 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.


Creatinine Range

  • The normal range of serum creatinine levels is 0.7-1.3 mg/dL (62-115 µmol/L)
  • High values (>1.3 mg/dL) can be caused by: kidney disease or high contribution of muscle mass to total body weight.
  • Low values (<0.7 mg/dL) can be caused by: malnourishment, muscle atrophy, or severe liver disease.


Sign of Kidney Problems to Check BUN Creatinine Ratio

  • A change in how much you urinate
  • Pee that is foamy, bloody, discolored, or brown
  • Pain while you pee
  • Swelling in your arms, hands, legs, ankles, around your eyes, face, or abdomen
  • Restless legs during sleep
  • Pain in the mid-back where kidneys are located
  • You’re tired all the time


Risk of BUN Creatinine Ratio

  • Unless you’re seeking care for an emergency medical condition, you can typically return to your normal activities after taking a BUN Creatinine Ratio test.
  • Tell your doctor if you have a bleeding disorder or you’re taking certain medications such as blood thinners.
  • This may cause you to bleed more than expected during the test.


Side effects associated with a BUN Creatinine Ratio test include:

  • Bleeding at the puncture site
  • Bruising at the puncture site
  • Accumulation of blood under the skin
  • Infection at the puncture site



Overall, BUN Creatinine Ratio helps to find out patient's blood urea nitrogen to their creatinine levels . Notify your doctor if you experience any unexpected or prolonged side effects after the test. Check more medical calculators like this to solve your daily problems on Drlogy Calculator to get exact solution.



  • Blood urea nitrogen by Wikipedia [1].
  • Urea-to-creatinine ratio by Wikipedia [2].


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BUN Creatinine Ratio Calculator FAQ

What is a normal BUN creatinine ratio?

  • The ideal ratio of BUN to creatinine falls between 10-to-1 and 20-to-1.
  • Having a ratio above this range could mean you may not be getting enough blood flow to your kidneys, and could have conditions such as congestive heart failure, dehydration, or gastrointestinal bleeding.

How to calculate BUN Creatinine Ratio?

You can calculate BUN Creatinine Ratio by this formula.

BUN Creatinine Ratio = BUN / Creatinine

How do I calculate the BUN-to-creatinine ratio?

To calculate the bun creatinine ratio:

  • Determine the patient's blood urea nitrogen (BUN) and serum creatinine levels.
  • Make sure the units are the same – usually mg/dL.
  • Divide BUN by serum creatinine to obtain the BUN creatinine ratio.

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