What is the BUN test?
The blood urea nitrogen (BUN) test is a test of how well your kidneys are working. It measures the amount of nitrogen in your blood. The nitrogen is present in a chemical called urea. Urea is a waste product produced as your body digests protein. Urea is carried by the blood to the kidneys, which filter the urea out of the blood and into the urine.
Why is this test done?
BUN is usually measured to see how well your kidneys are working. Kidney disease often makes it hard for the kidneys to filter as much urea as they should. This causes high levels of urea in the blood. This test is also done if you are having kidney dialysis to see how well the dialysis is working. This test may be used with another test called the creatinine test to see if you are dehydrated. Some medicines are processed by the kidneys or can cause kidney damage as a side effect. The BUN test may be done to be sure you have normal kidney function before you start taking these medicines.
What does the test result mean?
The normal range for BUN is 7 to 20 milligrams per deciliter (mg/dL). The normal range may vary slightly from lab to lab. Normal ranges are usually shown next to your results in the lab report. Your BUN level may be higher than normal because:
Your kidneys aren't working well. You have low levels of fluid in your body (you are dehydrated). You've been eating a high-protein diet. You are bleeding into your stomach (from an ulcer, for example). You have heart failure or you've had a heart attack. You are in shock. Your urinary tract is blocked (for instance, from an enlarged prostate in men or from a kidney stone or tumor).
How To Prepare Do not eat a lot of meat or other protein in the 24 hours before having a blood urea nitrogen (BUN) test. Blood urea nitrogen (BUN)
10–20 milligrams per deciliter (mg/dL) or 3.6–7.1 millimoles per liter (mmol/L)