BUN stands for Blood Urea Nitrogen, which is a common blood test that measures the amount of urea nitrogen in your blood. Urea nitrogen is a waste product that your body makes after it breaks down protein, and healthy kidneys take urea nitrogen out of your blood. When your kidneys are not working well, your BUN level goes up.

The BUN test is used to reveal important information about how well your kidneys are working. A healthcare provider may recommend a BUN test during a routine checkup as part of a comprehensive metabolic panel (CMP) or basic metabolic panel (BMP) blood test. A provider may also recommend a BUN test if you have a higher risk of kidney disease. The early stages of kidney disease usually do not have any symptoms, but the following factors may put you at a higher risk:

• Biological family history of kidney disease
• Diabetes
• High blood pressure (hypertension)
• Heart disease

If you have symptoms of later-stage kidney disease, it’s a good idea to get a BUN test. Symptoms of later-stage kidney disease may include needing to urinate more than usual, foamy pee, blood in your pee, fatigue, loss of appetite, and swelling, particularly in your hands, feet, or ankles.

A BUN test can reveal whether your urea nitrogen levels are higher than normal, suggesting that your kidneys may not be working properly. The normal BUN level is between about 7 to 20 milligrams per deciliter (mg/dL) . A higher than normal BUN level may be a sign that your kidneys are not working well. However, several things can affect your BUN test results, so having a BUN level that is lower or higher than the normal range doesn’t always mean there is a problem.