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Blood Urea Nitrogen BUN-Creatinine Ratio

Also Known As: Blood Urea Nitrogen, BUN, Urea Nitrogen, BUN to Creatinine Ratio

What is A BUN Blood Test?

BUN Blood test or Blood Urea Nitrogen test measures the amount of nitrogen in a blood sample. Urea is a waste product produced by the body during the normal breakdown of proteins. It's also known as urea nitrogen, and the kidneys filter it out of the blood. As your liver produces urea daily, some urea in the blood is natural, but too much of it can indicate a problem in your kidney.

What Is A Creatinine Blood Test?

Another chemical produced from muscle metabolism is creatinine. Creatinine, like urea, is carried through the bloodstream to the kidneys, where it is filtered and expelled in the urine. An individual's muscle mass determines the rate at which creatinine is formed.

Creatinine levels are usually stable throughout the day because muscle mass remains relatively constant. When a creatinine test reveals high levels, it may indicate impaired kidney function penal or kidney disease.

What Is BUN Creatinine Ratio in Blood Test?

Doctors can calculate the BUN creatinine ratio by combining the results of both the BUN and the Creatinine blood tests. The BUN creatinine ratio tests are good techniques for independently checking liver and kidney function. But when they are combined, clinicians gain a far better knowledge of your kidney health and can provide a more accurate diagnosis of kidney-related problems and treat them in time.

The BUN/Creatinine Ratio Test measures BUN and creatinine levels to evaluate how well the kidneys function. Your doctor usually orders this test with a full renal or electrolyte panel. While blood urea nitrogen is the metabolic result of the liver and creatinine is the product of muscle activity, the blood eliminates both combined. The ratio between them can explain many malfunctions.

What Is BUN Creatinine Ratio in Blood Test Used For?

A BUN Creatinine Ratio test may be recommended as part of a routine visit by your doctor. If you have a kidney issue, the test will determine your BUN levels before you begin treatment or medication. The BUN/Creatinine Ratio test may be ordered if your doctor fears developing kidney problems.

The purpose of a BUN/Creatinine Ratio test is to assess the health of your kidneys, detect kidney disease, and track the effectiveness of therapies for kidney disease or damage. The BUN/creatinine ratio test findings have shown to be one of the most effective techniques to diagnose acute or chronic renal illness, gastrointestinal bleeding, and urinary tract obstructions. Furthermore, there is virtually no risk associated with this test.

Why and when do you need to get tested?

If you have kidney disease symptoms, a panel of tests, including a BUN measurement, will be recommended to you by your doctor after careful evaluation. Additionally, whether you have nonspecific symptoms or are being assessed in an emergency hospital or urgent care setting, a test panel with BUN may be used to aid in diagnosis.

Suppose you have risk factors for kidney disease, such as a family history of kidney disease, diabetes, or cardiovascular disorders like high blood pressure. In that case, your doctor may offer screening tests, including a BUN measurement.

You should get tested if:

  • You have some kidney damage or disease.
  • You experience a burning sensation while urinating.
  • High blood pressure
  • You notice a change in the color of your urine.
  • Excessive fatigue
  • Swelling in feet and ankles
  • Loss of appetite
  • Puffy and red eyes

What kind of sample is required for the Bun Blood test?

Trained healthcare providers collect samples. The samples, after collection, are then sent to the lab for analysis. BUN Blood test can be conducted on two types of samples:

  • Urine
  • Blood


Your doctor may ask you to collect all of your urine within 24 hours. You will be given a container to collect your urine. You will be provided instructions on collecting and keeping your samples by your healthcare physician or a laboratory specialist.


A tiny needle will be used to collect a blood sample from a vein in your arm by a health care provider. Only a small amount of blood will be collected into a test tube by a professional once the needle is inserted. The procedure is not painful; it may sting a little when the injection is inserted. It usually takes less than five minutes to complete this task.

Do you need to prepare for the BUN Blood test?

Tell your doctor about any medications you're taking before the BUN blood test. Your doctor may ask you to stop taking any of them for a time if any of them could affect the test results.

You can eat and drink if you're only getting a BUN/Creatinine Ratio. However, if you have additional blood tests, your doctor may give you instructions, including fasting before the test. Avoid eating cooked meat 24 hours before the test, as it can cause high creatinine levels. 

Are there any risks to this Bun Blood test?

There is no need to get worried about any side effects or risks; there are absolutely no risks in getting a BUN blood test or a urine test. After the sample is collected, you can resume your daily activities almost immediately. 

What does the test result mean?

The formula is simple: Divide the BUN count by the creatinine count to get a BUN/Creatinine ratio. The bun-to-creatinine ratio should usually be between 10-1 and 20-1. This is a rough estimate that varies depending on age and gender. 

A higher ratio could mean you're becoming older and have relatively less muscle mass. Ratios outside normal ranges can be problematic if caused by high BUN levels rather than low creatinine levels. Liver disease can cause a lower BUN level. Moreover, a low BUN level is common in the second or third trimester of pregnancy.

Congestive heart failure, gastrointestinal bleeding, or severe dehydration can all be revealed by an unusually high ratio. A BUN/Creatinine ratio lower than the recommended range may indicate liver illness or malnutrition.

Related Tests: Renal Panel test, Basic Metabolic Panel (BMP blood test), Comprehensive Metabolic Panel (CMP blood test), Creatinine serum, Creatinine urine test, creatinine clearance, Estimated Glomerular Filtration Rate (eGFR)

Our clinical experts continually monitor the health and medical content posted on CURA4U, and we update our blogs and articles when new information becomes available. Last reviewed by Dr.Saad Zia on December 19th, 2023. 


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