What is Blood Urea Nitrogen (BUN) Test?
A blood urea nitrogen (BUN) test is used to determine how well your kidneys are working. It does this by measuring the amount of urea nitrogen in the blood. Urea nitrogen is a waste product that’s created in the liver when the body breaks down proteins. Normally, the kidneys filter out this waste, and urinating removes it from the body.
BUN levels tend to increase when the kidneys or liver are damaged. Having too much urea nitrogen in the blood can be a sign of kidney or liver problems.
Why is Blood Urea Nitrogen (BUN) Test performed?
You may need a blood urea nitrogen test:
- If your doctor suspects that you have kidney damage
- If your kidney function needs to be evaluated
- To help determine the effectiveness of dialysis treatment if you’re receiving hemodialysis or peritoneal dialysis
- As part of a blood test group to help diagnose a number of other conditions, such as liver damage, urinary tract obstruction, congestive heart failure or gastrointestinal bleeding — although an abnormal BUN test result alone doesn’t confirm any of these conditions
If kidney problems are the main concern, the creatinine levels in your blood will likely also be measured when your blood is tested for urea nitrogen levels. Creatinine is another waste product that healthy kidneys filter out of your body through urine. High levels of creatinine in your blood may be a sign of kidney damage.
Your doctor may also test how well your kidneys are removing waste from the blood. To do this, you may have a blood sample taken to calculate your estimated glomerular filtration rate (GFR). The GFR estimates the percentage of kidney function you have left.
What should I know before receiving Blood Urea Nitrogen (BUN) Test?
Side effects associated with a BUN test include:
- Bleeding at the puncture site
- Bruising at the puncture site
- Accumulation of blood under the skin
- Infection at the puncture site
In rare cases, people become lightheaded or faint after having blood drawn. Notify your doctor if you experience any unexpected or prolonged side effects after the test.
How to prepare for Blood Urea Nitrogen (BUN) Test?
If your blood sample is being tested only for blood urea nitrogen, you can eat and drink normally before the test. If your blood sample will be used for additional tests, you may need to fast for a certain amount of time before the test. Your doctor will give you specific instructions.
What happens during Blood Urea Nitrogen (BUN) Test?
A BUN test is a simple test that involves taking a small sample of blood.
Before drawing blood, a technician will clean an area of your upper arm with an antiseptic. They’ll tie an elastic band around your arm, which will make your veins swell with blood. The technician will then insert a sterile needle into a vein and draw blood into a tube attached to the needle. You may feel mild to moderate pain when the needle goes in.
Once they collect enough blood, the technician will remove the needle and apply a bandage over the puncture site. They’ll send your blood sample to a laboratory for testing. Your doctor will follow up with you to discuss the test results.
What happens after Blood Urea Nitrogen (BUN) Test?
Unless you’re seeking care for an emergency medical condition, you can typically return to your normal activities after taking a BUN test.
If you have any questions about the Blood Urea Nitrogen (BUN) Test, please consult with your doctor to better understand your instructions.
Explanation of results
What do my results mean?
Results of a BUN test are measured in milligrams per deciliter (mg/dL). Normal BUN values tend to vary depending on gender and age. It’s also important to note that each laboratory has different ranges for what’s normal.
In general, normal BUN levels fall in the following ranges:
- Adult men: 8 to 24 mg/dL
- Adult women: 6 to 21 mg/dL
- Children 1 to 17 years old: 7 to 20 mg/dL
Normal BUN levels for adults over 60 are slightly higher than normal levels for adults under 60.
Higher BUN levels can indicate:
- Heart disease
- Congestive heart failure
- A recent heart attack
- Gastrointestinal bleeding
- High protein levels
- Kidney disease
- Kidney failure
- Obstruction in the urinary tract
Keep in mind that some medications, such as certain antibiotics, can raise your BUN levels.
Lower BUN levels can indicate:
- Liver failure
- Severe lack of protein in the diet
Depending on your test results, your doctor may also run other tests to confirm a diagnosis or recommend treatments. Proper hydration is the most effective way to lower BUN levels. A low-protein diet can also help lower BUN levels. A medication wouldn’t be recommended to lower BUN levels.
However, abnormal BUN levels don’t necessarily mean you have a kidney condition. Certain factors, such as dehydration, pregnancy, high or low protein intake, steroids, and aging can impact your levels without indicating a health risk.
Depending on the laboratory and hospital, the normal range for Blood Urea Nitrogen (BUN) Test may vary. Please discuss with your doctor any questions you may have about your test results.
Hello Health Group does not provide medical advice, diagnosis or treatment.
Blood Urea Nitrogen (BUN) Test. https://www.healthline.com/health/bun. Accessed October 9, 2018.
Blood urea nitrogen (BUN) test. https://www.mayoclinic.org/tests-procedures/blood-urea-nitrogen/about/pac-20384821. Accessed October 9, 2018.
Review Date: November 4, 2018 | Last Modified: November 4, 2018