How the BUN Blood Test Helps Track Kidney Function

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BUN stands for blood urea nitrogen. This is a waste product that is produced during the digestion of protein by the human body. When blood travels to the kidneys to be filtered, it carries urea with it, and the kidneys filter the waste product out of the blood (University of Michigan Health System). When the kidneys are not functioning properly, they may not be able to filter urea out of the blood adequately. The BUN blood test allows doctors to assess how well a patient’s kidneys are functioning.

Purpose of BUN Blood Test

Healthy patients may have a BUN blood test performed along with routine blood tests during an annual physical or during an insurance exam. Patients with kidney function problems may have the BUN blood test performed on a regular outpatient basis or daily after they have been admitted to a hospital for medical care. The BUN blood test is often performed alongside a blood test that measures the amount of creatinine in the blood. The BUN blood test, along with a creatinine measurement, can help provide a picture of how well kidneys are working or how poorly they are functioning.

Another purpose of the BUN blood test is to measure kidney function before certain drugs are prescribed. Because some drugs are metabolized through the kidneys, they can put a strain on the kidneys if used for more than a short period of time. Your doctor may ask you to have a BUN blood test to determine how well your kidneys are functioning before such a drug is prescribed for your use (University of Michigan Health System).

BUN Blood Test Results

While normal BUN values differ slightly based on which laboratory is used to process the test, the normal range is usually between 7 and 20 mg/dL of BUN. Your BUN blood test results may be high for several reasons. These reasons include dehydration, eating a high protein diet, reduced kidney function, blockage of the urinary system, or a bleeding condition that causes you to bleed into the stomach. The BUN blood test results may also be low. Low levels of BUN in the blood can be caused by reduced liver function, low protein diets, excess fluid intake, and malnourishment. Some antibiotics and other drugs, such as diuretics, can also cause higher than normal BUN blood test results (University of Michigan).

BUN Blood Test Reference Materials

University of Michigan Health System. Health Topics A to Z. “BUN (Blood Urea Nitrogen) Test.” Retrieved: January 23, 2009. Available: University of Michigan Health System