Blood Urea Nitrogen Test (BUN) – Why am I having this test?
Blood urea nitrogen test is used to evaluate kidney and liver function and to monitor people with kidney problems or kidney failure.
Many diseases or conditions that affect the kidneys or liver can affect the amount of urea in your blood.
The BUN test is often done during routine lab testing. It is usually interpreted along with a test called a creatinine test. The BUN/creatinine ratio is a good indicator of kidney and liver function.
What is being tested?
The BUN test measures the amount of urea nitrogen in your blood. Urea nitrogen is made in the liver. It is a product of digestion and the breakdown of protein.
What kind of sample is taken?
A blood sample is required for this test. It is usually collected by inserting a needle into a blood vessel.
How are the results reported?
Your test result will be reported as a value. Your health care provider will compare your results to normal ranges that were established after testing a large group of people (reference ranges). Reference ranges may vary among labs and hospitals. For this test, common reference ranges are:
- Cord: 21–40 mg/dL.
- Newborn: 3–12 mg/dL.
- Infant: 5–18 mg/dL.
- Child: 5–18 mg/dL.
- Adult: 10–20 mg/dL or 3.6–7.1 mmol/L (SI units).
What do the results mean?
Abnormally high BUN levels may indicate:
- Kidney disease.
- Obstruction of the flow of urine.
- Overconsumption of protein.
- Excessive protein breakdown.
- Decrease in blood volume (hypovolemia).
- Gastrointestinal bleeding.
- Congestive heart failure.
- Acute heart attack (myocardial infarction, MI).
Abnormally low BUN levels may indicate:
- Liver failure.
- Excessive hydration.
- Low-protein, high-carbohydrate diets.
Talk with your health care provider about what your results mean.
Questions to ask your health care provider
Ask your health care provider, or the department that is doing the test:
- When will my results be ready?
- How will I get my results?
- What are my treatment options?
- What other tests do I need?
- What are my next steps?
- The blood urea nitrogen (BUN) test is used to check for kidney and liver function and to monitor people with kidney problems or kidney failure.
- The test measures the amount of urea nitrogen in your blood. High or low levels of urea may indicate the presence of certain conditions or diseases.
- Talk with your health care provider about what your results mean.