Bunbldvmcnc
A blood test that measures the amount of urea nitrogen in your blood to evaluate kidney function.
{"BUN test measures waste product levels in your blood from protein breakdown","High BUN levels may indicate kidney problems or dehydration","Low BUN levels can be related to liver disease or malnutrition","The test requires a simple blood draw from a vein"}
Key facts at a glance
- LOINC
- 12962-7
- Short code
- BUN
- Synonyms
- BUN BldV-mCnc
- Category
- chemistry
- Sample
- whole-blood
- Container
- SST (Serum Separator Tube - gold top) or plain red top tube; green top (lithium heparin) tube acceptable for plasma
- Units
- not specified
- Ref low
- 7
- Ref high
- 20
- Critical range
- 3 not specified – 100 not specified
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- ≥ 18 years
- Method
- Enzymatic (Urease) method using spectrophotometric detection
- CPT
- 84520
- SNOMED
- 271565004
- Specimen volume
- 1-2 mL of venous blood
- Stability
- Room temperature: 24 hours; Refrigerated (2-8°C): 72 hours; Do not freeze
- Hemolysis max
- 50
- Lipemia max
- 60
- Icterus max
- 40
- TAT
- 1–4 hours
- Order
- routine
What is this test?
The Blood Urea Nitrogen (BUN) test measures the amount of urea nitrogen in your blood. Urea nitrogen is a waste product that forms when your body breaks down protein from foods and normal cell breakdown. Normally, your kidneys filter urea nitrogen from your blood and remove it through urine. The BUN test helps doctors see how well your kidneys are working.
Why is this test done?
Your doctor may order a BUN test as part of a routine health checkup or to: check how well your kidneys are working, monitor kidney disease or damage, evaluate dehydration, check the effectiveness of certain medications, or investigate urinary tract problems.
How is the test performed?
A healthcare professional will draw a small sample of blood from a vein in your arm using a needle. The blood sample is then sent to a laboratory for analysis. You do not need to fast before this test, but your doctor may ask you to avoid certain medications or supplements beforehand. The test is quick and generally causes minimal discomfort.
Understanding your results
Normal BUN ranges vary by laboratory but are typically between 7 to 20 mg/dL (milligrams per deciliter). Your result depends on factors like age, sex, diet, and overall health. Your doctor will interpret your results in context of your overall health and other test results.
Reference range
7-20 mg/dLnot specified
No fasting or special preparation required
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Frequently asked questions
Do I need to fast before a BUN test?
What can cause high BUN levels besides kidney problems?
Is a BUN test dangerous?
How often should I have a BUN test?
Sources
- 1
- 2
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 10, 2026. · Read our editorial policy