BUN Blood Test – Normal, High and Low Levels (Interpretation)

BUN or Blood Urea Nitrogen test is used to reveal vital information about the kidneys and liver. It determines how well your kidneys and liver are working. It does so by measuring the level of urea nitrogen in the blood level.

Urea Nitrogen is a waste that gets created inside the liver at the time the body breaks protein. Later kidneys filter the waste in the body and it is eliminated through the process of urine.

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The BUN level goes higher in case the kidneys or the livers get damaged. In case of too much urea nitrogen in the blood, it is advisable to consult a doctor as it is a sign of having damaged kidneys.


How Does Body Clears Out Urea Nitrogen?

Liver produces ammonia once it breaks down protein which is used by the body cells. The ammonia contains nitrogen which is combined with other elements like carbon, hydrogen or oxygen to create urea.

This waste product then travels from the liver to kidneys. If the kidneys are healthy, the urea gets filtered and eventually leaves the body through urine.

Why is BUN Important?

BUN is a simple test which does not take much time. This is done to determine the function of the kidney. Often this test is done along with other tests to perform a proper diagnosis.

BUN helps in diagnose a lot of health conditions. Liver damage is one of the major condition that BUN helps in determining. It can be performed to diagnose malnutrition as well. Poor blood circulation is another health condition which BUN diagnoses. Dehydration can be a serious health condition which BUN can diagnose. Sometimes BUN is performed to determine urinary tract obstruction too.


How to Prepare for the Test?

The BUN test is a simple test which does not need any special preparation. However, if you are under any kind of medication, you will have to tell your doctor about that. Some medications can affect the result of BUN. In such cases doctor might ask you to stop taking the medication or reschedule the date of the test.

The doctor might ask you not to eat a lot of meat before the test. However, if it is only your blood sample which gets tested, you might enjoy regular meal. In case the blood sample will be used for any other test, you might have to fast the previous day. However, your doctor is the ideal person to provide you the right information.


How is the BUN Test performed?

The test involves taking a small quantity of blood sample. Before getting the blood sample, the doctor or a technician clears an area on the arm. This is the spot from where the blood gets drawn. To make the procedure easy and painless, the technician will tie an elastic band around the arm. This will help the veins of the arm to swell out. The technician then inserts the needle to get the blood out. This is painless, however, you might feel slight pain around your arm.

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Once the blood sample is taken out, the technicians will send it to the laboratory for further testing.


Is There Any Risk?

 There is no great risk involved with this test. However, some unwanted effect might occur as the result of the test. You might experience small bruises on the area from where the blood has been removed. In some very rare cases, the vein gets swollen. Bleeding can be a problem which many have experienced during the test.

Some patients who have been through this test has complained feeling faint after the test. Accumulation of blood under the skin is another problem which you might face after the BUN test.

BUN Test Results – Interpretation

The result is measured in milligram. The normal BUN value varies depending on the age and the gender of the patient. High BUN level may indicate congestive heart attack or heart failure, high protein level, kidney failure, shock, dehydration and obstruction in urinary tract.

Lower BUN level indicates the sign of liver failure, malnutrition, lack of protein in the diet. Depending on the test result, the doctor may prescribe  particular line of treatment


 BUN – Normal Range

The normal range of the BUN level is adults 10 to 20 milligrams per deciliter. For children 5 to 18 mg per dL. The BUN to creatinine ratio is 6 to 25. However, you need to remember that the range may vary depending on the lab you are getting the test done from.


High BUN Levels

High BUN value may mean that the kidney is affected by injury or disease. Such injury or damage can be caused by high blood pressure or diabetes. Some medicines may cause high BUN as well.


Low Bun Levels

Low BUN may get caused by low protein diet. Drinking too much liquid sometimes causes over-hydration and eventually this leads to low BUN level. Women and children might have low BUN level as their bodies use different methods to break protein than men.


BUN and Creatinine Test     


The BUN test might be done alongside a blood creatinine test. BUN and creatinine tests can be done together as well to determine the blood creatinine levels in the body. The BUN level might be measured in people with kidney dialysis. Also, it is used to check how well the dialysis is working.

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