Contributed by Healthians Team

What is a blood urea nitrogen serum test?

A blood urea nitrogen (BUN) test is used to determine how well your kidneys are working. It measures the amount of urea nitrogen present in your blood. Urea nitrogen is a waste product created when your body breaks down proteins. Generally, this gets removed from the body after urinating. BUN levels tend to rise when either your kidney or liver is damaged. An excess of urea nitrogen in your blood can signify kidney or liver complications.

Your liver produces ammonia which contains nitrogen after breaking proteins for your cells. This nitrogen combines with other elements such as carbon, hydrogen, and oxygen to form urea which is a waste product. This urea travels from your liver to your kidneys through your bloodstream. Your healthy kidneys filter urea and remove waste from your blood which leaves your body through urine.

Who should get the test?

This test is most commonly used to evaluate kidney function. It is often done along with other blood tests such as a creatinine blood test for proper diagnosis. You might need a blood urea nitrogen test if your doctor suspects that you have kidney damage or your kidney function needs to be evaluated. It also helps to determine the efficiency of dialysis treatment if you’re receiving hemodialysis or peritoneal dialysis. BUN tests are also performed as part of regular checkups or after treatment for conditions such as diabetes.

Why is the test needed?

The BUN test is used as part of a blood test group that aids diagnosis of a number of other conditions such as liver damage, urinary tract obstruction, congestive heart failure, or gastrointestinal bleeding. In case of kidney problems being the main concern, your creatinine levels will be measured while testing for urea nitrogen levels. Creatinine is another waste product that healthy kidneys filter out of your body through urine. High levels of creatinine in your blood might indicate kidney damage. Your doctor might also test how well your kidneys are removing the waste from your blood.

What does the test result mean?

Results of the blood urea nitrogen test are measured in milligrams per deciliter (mg/dL) in the United States and in millimoles per liter (mmol/L) internationally. Around 7 to 20 mg/dL (2.5 to 7.1 mmol/L) is considered normal. However, the normal ranges might vary depending on the reference range used by the lab and your age.

Urea nitrogen levels tend to increase with your age. The infants have lower nitrogen levels and the range in children fluctuates. Usually, a high blood urea nitrogen level means your kidneys are not functioning properly. However, your elevated blood urea nitrogen can be due to urinary tract obstruction, congestive heart failure, or a recent heart attack. Apart from this if you are suffering from gastrointestinal bleeding, dehydration, shock, severe burns, a high-protein diet, and certain medications such as antibiotics then you might experience an increased blood urea nitrogen.

How is the test done?

During the blood urea nitrogen test, a lab technician takes a sample of blood by inserting a needle into a vein of your arm. This blood sample is sent to a lab for analysis. The process doesn’t require much time.

Take the Blood Urea Nitrogen Test