What is BUN?

What is BUN?

The blood urea nitrogen (BUN) test measures the level of urea nitrogen in a sample of the patient's blood. Urea is a substance that is formed in the liver when the body breaks down protein. Urea then circulates in the blood in the form of urea nitrogen. In healthy people, most urea nitrogen is filtered out by the kidneys and leaves the body in the urine. If the patient's kidneys are not functioning properly or if the body is using large amounts of protein, the BUN level will rise. If the patient has severe liver disease, the BUN will drop.

Why It Is Done?

A blood urea nitrogen (BUN) test is done to:

-See if your kidneys are working normally.

-See if your kidney disease is getting worse.

-See if treatment of your kidney disease is working.

-Check for severe dehydration. Dehydration generally causes BUN levels to rise more than creatinine levels. This causes a high BUN-to-creatinine ratio. Kidney disease or blockage of the flow of urine from your kidney causes both BUN and creatinine levels to go up.

How is the test done?

When a blood sample from a vein is needed, a vein in your arm is usually selected. A tourniquet (large rubber strap) may be secured above the vein. The skin over the vein will be cleaned, and a needle will be inserted. You will be asked to hold very still while your blood is collected. Blood will be collected into one or more tubes, and the tourniquet will be removed. When enough blood has been collected, the healthcare worker will take the needle out.

Normal BUN levels

Without changes of diet and lifestyle, healthy kidneys are usually able to keep blood urine nitrogen level in a normal range. Blood urea nitrogen test is measured in milligrams per deciliter (mg/dl) in America and in millimoles per liter (mmol/L) internationally.

Normal blood urea nitrogen level is 7 to 20 mg/dL (2.5 to 7.1 mmol/L).

However, normal blood urine nitrogen may vary which depends on the reference range used by the lab and your age. Besides, blood urea nitrogen levels increase with age. Infants usually have lower urea nitrogen levels than other people do and the range varies from different infant to infant.

Normal BUN for adults is 12 to 20.

BUN in children and infants is 5 to 18.

BUN in newborns is 3 to 12.

Blood urea nitrogen is 21 to 40 for cold blood.

In the elderly, the blood urea nitrogen is a little higher than normal adult range.

And also there is a maximum limit of normal blood urea nitrogen which can reach 25mg/dl. If some day your lab test shows your blood urea nitrogen is higher than normal, it may indicate some underling conditions.

Abnormally low BUN

Low levels of BUN may indicate overhydration, malnutrition, celiac disease [a disease characterized by the inability ot tolerate foods containing wheat protein (gluten)], liver damage or disease, or use of corticosteroids. Low BUN may also occur in early pregnancy.

Abnormally high BUN

High levels of BUN may indicate kidney disease or failure; blockage of the urinary tract by a kidney stone or tumor; a heart attack or congestive heart failure;dehydration; fever; shock; or bleeding in the digestive tract. High BUN levels can sometimes occur during late pregnancy or result from eating large amounts of protein-rich foods. A BUN level higher than 100 mg/dL points to severe kidney damage.

If you have been diagnosed with kidney disease, we're here to help. Email us: Emily1@yahoo.com (Monday through Sunday) to make an appointment.