Blood urea nitrogen (BUN) test for kidney disease
Learn about the blood urea nitrogen (BUN) test for kidney disease and find what your results mean.
- Medically reviewed by
- AKF's Medical Advisory Committee
- Last updated
- October 9, 2025
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What is BUN?
Your blood urea nitrogen (BUN) level is based on a 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. Healthy kidneys take urea nitrogen out of your blood. When your kidneys are not working well, your BUN level goes up.
How do I find out my BUN level?
To find out your BUN level, you will have your blood drawn at your doctor's office to see how much urea nitrogen is in your blood. It will take a few days before your BUN results come back. Then, your doctor will follow up to review the results with you.
What does my BUN test result mean?
BUN test results are measured in milligrams per deciliter (mg/dL). What is considered a normal BUN level depends on your age and other health conditions you may have. In general, about 7 - 20 mg/dL is a normal level.
A higher than normal BUN level may be a sign that your kidneys are not working well.
Your doctor will compare your BUN results along with other test results, such as creatinine and eGFR (estimated glomerular filtration rate), to decide on next steps.
What should I do after I get my test results?
No matter what your test results are, it is a good idea to ask your doctor these questions:
- What do my test results mean?
- What other tests should I have done?
- When should I get tested again?
You can also take steps to keep your kidneys as healthy as possible:
- Keep a healthy blood pressure (less than 120/80 for most people)
- Control your blood sugar if you have diabetes
- Eat fresh fruits and vegetables every day
- Eat foods low in salt and low in saturated fat
- Be active for at least 30 minutes most days of the week
- Keep a healthy weight
- Do not smoke or use tobacco
- Talk to your doctor about medicines that might help protect your kidneys
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