BUN (Blood Urea Nitrogen) Test
A BUN (blood urea nitrogen) test measures the amount of urea nitrogen in your blood. Urea nitrogen is a waste product from protein breakdown. Your kidneys remove it when you urinate. High levels may mean your kidneys aren't working well. Low levels may be due to liver disease or poor nutrition.
What this test measures
A BUN test measures the amount of urea nitrogen in your blood. Urea nitrogen is a waste product that forms when your body breaks down proteins. It is carried in your blood and removed by your kidneys when you urinate.
What your results mean
Reference ranges vary by laboratory and by your age and sex. MedlinePlus does not publish a single normal range for this test — always read your result against the range printed on your own lab report and discuss it with your provider.
Higher-than-normal results
According to MedlinePlus, a high blood urea nitrogen level is a sign that your kidneys are not working well. Other reasons include dehydration, burns, certain medicines, a high-protein diet, or a recent heart attack.
Lower-than-normal results
According to MedlinePlus, lower than normal BUN levels may be due to a lack of protein in your diet, malnutrition, or liver disease.
Frequently asked questions
What does BUN stand for?
BUN stands for blood urea nitrogen.
What does a BUN test measure?
It measures the amount of urea nitrogen in your blood, a waste product from protein breakdown.
Why is a BUN test done?
It helps diagnose or monitor kidney diseases and can uncover kidney problems early.
What can cause high BUN levels?
High BUN levels may be due to kidney problems, dehydration, burns, certain medicines, a high-protein diet, or a recent heart attack.
What can cause low BUN levels?
Low BUN levels may be due to a lack of protein in your diet, malnutrition, or liver disease.
Related lab tests
Sources
- MedlinePlus: BUN (Blood Urea Nitrogen) — NIH MedlinePlus
Last updated . Information is aggregated from official public sources and is not a substitute for professional medical care.