Serum or plasma mass concentration of urea nitrogen (BUN)
This test measures the amount of nitrogen found in your blood that comes from urea, a waste product from protein metabolism. It helps assess kidney function by determining how well your kidneys filter waste from your blood.
["A BUN test helps doctors check kidney health and diagnose conditions like kidney disease or dehydration."]
Key facts at a glance
- LOINC
- 50592-5
- Short code
- EME Ur Cfm-mCnc
- Synonyms
- EME Ur Cfm-mCnc
- Category
- chemistry
- Sample
- urine
- Container
- Sterile urine container
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- confirm
- Specimen volume
- 10 mL
- Stability
- Room temperature: 2h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 4–24 hours
- Order
- routine
What Is a BUN Test Used For?
Doctors use a BUN test to evaluate kidney function, monitor kidney-related conditions, and assess overall hydration status. It can also help identify issues like kidney failure, urinary tract blockages, or dehydration. Sometimes, it’s used alongside other tests, like creatinine levels, to get a clearer picture of kidney health.
How Is the BUN Test Performed?
A blood sample is taken from a vein, usually in your arm. The sample is then sent to a lab to measure the urea nitrogen concentration. No special preparation is needed, but you may be asked to avoid certain foods or fluids for a few days before the test if instructed by your doctor.
What Are Common Causes of High or Low BUN Levels?
High BUN levels may indicate problems like kidney disease, dehydration, heart failure, or conditions that increase blood urea nitrogen production (e.g., severe infections or high protein diets). Low BUN levels can sometimes suggest overhydration, liver disease, or malnutrition, though this is less common.
How Does the BUN Test Relate to Kidney Function?
The BUN test is part of a broader assessment of kidney function. While it provides insight into how well your kidneys filter waste, doctors often compare it with other tests, like creatinine levels, to get a fuller understanding of kidney health and efficiency.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
The BUN test is critical for diagnosing and monitoring kidney-related issues, detecting dehydration, and assessing how well your body processes waste. It can also help identify underlying conditions that may affect kidney function, such as heart disease or infections. Regular monitoring of BUN levels can help prevent complications and guide treatment decisions.
Short name
BUN (Serum/Plasma)
Frequently asked questions
What factors might affect my BUN test results?
Do I need to prepare for this test?
Can BUN levels change quickly, or is this a long-term indicator?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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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 16, 2026. · Read our editorial policy