blood urea nitrogen (bun) Test


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clinical definition of blood urea nitrogen

Urea is made when protein is broken down in your body. Urea is made in the liver and passed out of your body in the urine. The blood urea nitrogen level rises if the kidneys are unable to remove urea from the blood normally. Heart failure, dehydration, or a diet high in protein can also increase the BUN level. Reduction of the blood urea nitrogen level may occur in case of liver disease or damage. A blood creatinine test may be done along with a BUN test since the level of creatinine in the blood also indicates the working of the kidneys.

what is a bun test?

The blood urea nitrogen test or commonly referred to as the bun test is a diagnostic tool used to measure the amount of nitrogen in your bloodstream. The test is recommended to see how well the kidneys and liver are functioning in the body. When there are abnormalities in the kidney and the liver function the bun level tends to increase. The bun blood test can help diagnose kidney problems at an early stage enhancing the chances of treatment.

why do i need bun test?

A BUN test is generally prescribed by a medical practitioner or a doctor to check if there is an anomaly in the functioning of the kidney and liver. The test is carried out to gain conclusive evidence if the patient is suffering from any of the below conditions.

• Dehydration

• Swelling in your arms, legs, or feet

• Recurring fatigue

• Needing to go the bathroom (urinate) frequently or infrequently

• Malnutrition

• Urinary Tract Obstruction

• Gastrointestinal Bleeding

• Congestive Heart Failure

Sometimes the BUN tests are also prescribed as a part of the health checks or also to gauge the effectiveness of existing dialysis treatment.

what other tests might i have along with bun test?

Sometimes along with the BUN test, the doctor may also order for creatinine test. It is nothing but waste from the muscles that filtered by the kidney. The BUN test is not a conclusive diagnostic test hence when coupled with the creatinine test it gives a clear picture of the kidney health. Ideally, the creatinine and BUN ratio should be between 10:1 to 20:1.

what do my test results mean?

Apart from understanding what is urea nitrogen in blood test, it is equally important to understand the results of the test. A typical bun test result will reveal low or high BUN levels if the kidneys are not functioning optimally. If the BUN levels are on the higher side, it implies problems in the kidney caused by high blood pressure, diabetes etc. Low bun levels are caused by conditions like malnutrition or a diet low in proteins etc. Any deviations from the normal bun levels should be immediately reported to the doctor.

how is bun test done?

The BUN test is a simple blood test. The technician wraps an elastic band on your upper arm to make the vein visible. The puncture site is cleaned with alcohol and the needle inserted to draw the blood sample. Once done the technician puts a gauze band or a cotton ball on the puncture site.

does bun test pose any risk?

The test does not pose any major risk. Sometimes all the patient might experience is slight pain or accumulation of blood on the puncture site. These side effects are tentative and tend to go away with time.

what might affect my test results?

Sometimes the patients requiring to undergo the test are already on medications. It is essential to tell your doctor about them as they can alter the test results. Some of the commonly prescribed medications that have a direct impact on the test results are methyldopa, Rifadin, Sumycin, vancomycin, cephalosporins and amphotericin B etc.

how do i prepare for bun test?

The test does not require any special preparation, and also you are not required to come empty stomach. But before the test, it is important to inform your doctor if you are on any kind of medication.

how do you understand the result?

The results of the test could be interpreted by using the blood urea nitrogen normal range as the reference. The following table will help you understand the results better as they provide detailed information on the bun normal range in adults and children.

what are the causes of blood urea nitrogen in blood and how to reduce it?

The causes of bun abnormalities are either due to problems and improper functioning of the kidney or restricted blood flow to the kidney. Either case the filtration task of the kidney will be hampered causing an increase of urea in the blood. Now the question arises how to reduce blood urea? Dietary changes increased intake of water, and restricted protein diet could be used as bun treatment. But if the problem persists consult your doctor for a further course of action.

Understanding results ofBlood Urea Nitrogen (BUN)

Reference RangeInterpretation
9 - 21 mg/dl"(13 - 18) yrs Child Age"
6 - 17 mg/dl(5Days - 2Yrs) Child Age
07 to 18 mg/dLMale/Female
3 - 19 mg/dl(0 - 4)days Child Age
8 - 18 mg/dl"(3 - 12) yrs Child Age"

‘*A Reference range is a set of values which helps the healthcare professional to interpret a medical test. It may vary with age, gender, and other factors. Reference ranges may also vary between labs, in value & units depending on instruments used and method of establishment of reference ranges’



The test can be carried out at any reputed hospital or a diagnostic centre. Depending upon where the tests are carried out there could be a variation in the bun test cost. One can also look for the bun test price in a particular centre or hospital online.

The BUN test is commonly used to find any deviations from the normal kidney functions quickly. It is also important to note that sometimes a deviation in the blood urea normal range might not indicate any kind of abnormality. Report to your doctor immediately so that they could order additional tests to reach a conclusive diagnosis.