HomeHealth A-ZBlood Urea Nitrogen or BUN Test

Blood Urea Nitrogen or BUN Test

The  liver breaks down the proteins in your food — and while doing so, liver creates blood urea nitrogen, also called BUN. Your liver releases this BUN into your blood, and it ends up eventually in your kidneys. Your kidneys, when they are healthy, removes the BUN, generally leaving a small amount of it in your blood. However, for the most part, your healthy kidneys discards it by flushing it out of your body through urine.

However, if your kidneys fail to function properly, the level of nitrogen and urea in your blood will rise. If you need to know the exact amount of urea currently present in your blood, you should undergo a Blood Urea Nitrogen test, which is called BUN in short.

About the BUN Test

The BUN test is a diagnostic procedure to check the health of your kidneys. Your blood sample is tested in the laboratory. Creatinine values may also be checked .

The level of urea and nitrogen will be higher in the cases of kidney problems, heart diseases, and dehydration. In contrast, the BUN level tends to be lower in patients suffering from liver diseases. 

However, the BUN report may show a higher value due to the intake of too much protein-rich food, while it can be lower during later stages of pregnancy. As it is done with a creatinine test, your doctor will compare both results to diagnose your exact problem.

Risk Factors Associated With the Bun Test

  • The spot punctured for taking the blood sample may bleed profusely if the patient has blood clotting issues or consumed blood-thinning medicines.
  • The bruise caused by the puncture may take some time to heal in the cases of diabetic patients.
  • The punctured site may turn red due to the accumulation of excess blood under the skin surface.

How to Prepare for the BUN Test?

You do not need to undergo any special preparation before a BUN test. You should only follow the instructions given by the doctor who recommended the test. 

However, you should inform your doctor about all the medications you are currently taking to avoid complications. 

Some medicines, like tetracycline, methyldopa, and carbamazepine, can raise your BUN level, and hence, your doctor may suggest stopping these medicines for the time being. You also need to limit your daily intake of fish, meat, and other protein-rich foods at least 24 hours before this test.

What to Expect from the BUN Test?

Only a tiny amount of your blood will be drawn for the BUN test. A lab technician will tie a band around your arm to dilate your veins for drawing the blood with a sterile syringe. You will experience mild pain, like a stinging sensation during this process, which should subside very soon. A bandage will be applied to this punctured area of your skin to stop the bleeding and heal it quickly. 

Subsequently, your blood sample will be tested with the necessary reagents to assess the urea and nitrogen levels in your blood. You can leave immediately after your blood sample is taken unless you experience any physical problem after the test.

Possible Results from Your BUN Test

The values on the BUN test report are expressed as milligrams per deciliter (mg/dL).  The standard BUN level depends on the age and gender of a patient. 

If an adult male patient’s test report is found to be normal, then his BUN level should be between 8 mg/dL and 24 mg/dL. 

The normal BUN report of an adult female patient should have a value ranging from 6 mg/dL to 21 mg/dL. Children up to 17 years should have a BUN level between 7 mg/dL and 20 mg/dL. 

However, the average range BUN value in aged men and women above the age of 60 is found to be a bit higher than the average BUN level of younger adults. If your BUN test report reveals a much higher or lower value than the normal range, you are most likely suffering from an ailment.

High levels may indicate the following:

  • Dehydration 
  • Kidney damage 
  • Shock
  • Urinary tract obstruction 
  • Burn injuries
  • Stress
  • Heart attack
  • Congestive heart failure (when heart does not pump blood to the body like it should)
  • Gastrointestinal bleeding (bleeding in the digestive tracts like esophagus, stomach, or intestines)

Low BUN levels are rare. If you have low BUN levels, it could indicate:

  • Liver disease
  • Overhydration (having too much fluid)
  • Malnutrition (when your diet does not have enough nutrients or your body cannot take them in well)

However, a BUN test is not a way to diagnose these issues, so more tests may be needed

When to See a Doctor?

If your BUN test report shows a much higher value than the normal range of your age group, it may be a sign of some underlying health conditions. You may be suffering from some cardiac problem, kidney failure, dehydration, injury in your gastrointestinal tract, or a blockage in your urinary tract. 

Abnormally high BUN levels may be due to the reactions of some medications that you are taking for curing other ailments. If you see a much lower BUN value than the normal range in your report, it may signify that you are suffering from liver damage or malnutrition. 

If you eat too little protein-rich foods or drink too much water, your BUN level may be lower than expected as well. However, the BUN levels may also become abnormal during pregnancy

It is best to see a doctor when you find a higher or lower BUN value in your BUN test report to ascertain the exact cause of this result.

Frequently Asked Questions (FAQs)

Is the BUN test a sign of kidney damage?

The BUN test is not only meant to detect kidney problems, as there are multiple reasons for the increase in the urea and nitrogen levels in your blood. So, you need not worry about your kidneys’ health when your doctor recommends conducting a BUN test. 

How can kidney failure be confirmed through the BUN test?

As the BUN test is usually done along with a creatinine test, your doctor can compare both results to determine your kidneys’ condition. The presence of a large amount of creatinine with a high BUN level in your blood can imply that your kidneys are not working properly.

How does the BUN test contribute to your kidney treatment?

In cases where the patients undergo peritoneal dialysis and hemodialysis, doctors need the current blood test reports to monitor the treatment and response. 
The BUN test report provides the levels of urea and nitrogen in patients’ blood and also shows the progress in their conditions after dialysis. Hence, doctors can decide whether to continue with further rounds of dialysis.

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At Apollo, we believe that easily accessible, reliable health information can make managing health conditions an empowering experience. AskApollo Online Health Library team consists of medical experts who create curated peer-reviewed medical content that is regularly updated and is easy-to-understand.
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