Blood Urea Nitrogen Calculator or BUN Calculator
Enter the serum urea value from your laboratory report to calculate the equivalent Blood Urea Nitrogen (BUN) concentration.
Calculation Details
What is Blood Urea Nitrogen (BUN)?
Urea is produced mainly in the liver during protein metabolism and is subsequently transported in the blood and excreted mainly through the kidneys.
Blood Urea Nitrogen (BUN) represents only the nitrogen portion of the urea molecule. Therefore, the BUN value is numerically lower than the serum urea concentration when both are expressed in mg/dL.
Why is BUN lower than serum urea?
Urea has a molecular weight of approximately 60 g/mol. The two nitrogen atoms account for approximately 28 g/mol. Therefore:
28 ÷ 60 ≈ 0.467
This is why: BUN ≈ Serum Urea × 0.467 when serum urea is expressed in mg/dL.
A commonly used adult BUN reference range is approximately 7–20 mg/dL. The exact reference interval varies by laboratory, age, population and assay. Always use the reference range provided with the patient's laboratory report.
What can influence BUN?
- Renal function and glomerular filtration
- Hydration and circulating volume
- Dietary protein intake
- Protein catabolism
- Gastrointestinal bleeding
- Liver function and urea synthesis
- Urinary tract obstruction
- Certain medications and systemic illnesses
BUN should not be interpreted alone
BUN is influenced by both renal and non-renal factors. Kidney assessment commonly also includes serum creatinine, estimated glomerular filtration rate (eGFR), urine findings and the overall clinical context.
References
- Hosten AO. BUN and Creatinine. In: Walker HK, Hall WD, Hurst JW, editors. Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd ed. Boston: Butterworths; 1990. NCBI Bookshelf
- Labcorp. Urea Nitrogen (BUN), serum/plasma. Enzymatic urease methodology. Laboratory Information
- Labcorp. SI Unit Conversion Table. Conversion information for urea nitrogen. SI Conversion Table
Blood Urea Nitrogen Calculator FAQs
Frequently asked questions about BUN, serum urea conversion, interpretation and laboratory units.
What is Blood Urea Nitrogen?
Blood Urea Nitrogen, or BUN, represents the nitrogen portion of urea circulating in blood.
What does this Blood Urea Nitrogen Calculator or BUN Calculator calculate?
This calculator converts serum urea into the equivalent Blood Urea Nitrogen value.
Should I enter serum urea or BUN?
Enter serum urea, not BUN. The calculator then converts the entered serum urea value to BUN.
Can serum urea be entered in mg/dL?
Yes. When serum urea is entered in mg/dL, the calculator multiplies it by approximately 0.467 to obtain BUN in mg/dL.
Can serum urea be entered in mmol/L?
Yes. When serum urea is entered in mmol/L, the calculator multiplies it by approximately 2.80 to obtain BUN in mg/dL.
What is the formula for converting serum urea to BUN?
For serum urea in mg/dL, BUN in mg/dL is approximately equal to serum urea multiplied by 0.467.
Why is BUN lower than serum urea in mg/dL?
BUN represents only the nitrogen portion of the urea molecule. The nitrogen atoms account for approximately 28 of the roughly 60 molecular-weight units of urea, giving a ratio near 0.467.
What is a commonly used adult BUN reference range?
A commonly used adult BUN reference interval is approximately 7–20 mg/dL, although laboratory-specific reference ranges should always be preferred.
What can cause a high BUN?
BUN can be influenced by renal function, dehydration, increased protein catabolism, gastrointestinal bleeding, high protein intake, urinary tract obstruction and other clinical factors.
What can cause a low BUN?
Lower BUN values may occur in situations such as reduced protein intake, impaired hepatic urea synthesis, overhydration and other clinical conditions.
Is BUN a kidney function test?
BUN is commonly used as part of kidney assessment, but it is influenced by both renal and non-renal factors and should not be interpreted alone.
Should BUN be interpreted with creatinine and eGFR?
Yes. Kidney assessment commonly includes serum creatinine, eGFR, urine findings and the overall clinical context in addition to BUN.
Does this Blood Urea Nitrogen Calculator or BUN Calculator automatically handle both urea units?
Yes. The calculator accepts serum urea in either mg/dL or mmol/L and applies the appropriate conversion automatically.
Is the Sensing Medicine Blood Urea Nitrogen Calculator or BUN Calculator free?
Yes. The Sensing Medicine Blood Urea Nitrogen Calculator is available as a free online clinical and educational calculator.
Is this a high-quality scientific Blood Urea Nitrogen Calculator or BUN Calculator?
The Blood Urea Nitrogen Calculator or BUN Calculator is designed as a high-quality, scientifically based clinical conversion tool using the established relationship between serum urea and Blood Urea Nitrogen and published laboratory references.
Features
- Health Blogs
- Free Multiple Choice Questions
- Awareness Campaigns
- Authentic Sources
- Neuro Rehab Games
Information
Follow Us
Disclaimer: We do not offer any kind of medical advice in any form. The information in the blog is not replacement of medical, diagnostic, endorsement, treatment, prescription or legal advice. The Blog is for informational purposes only. Although, we try to update but medical science is very vast and evolve at very fast pace. Nothing here should be used as a substitute for medical advice, diagnosis, or treatment. We do not endorse any healthcare advice that contradicts a physician's guidance. Kindly read our policies before reading the website content.
Placement of a link, graphic or text link is to be used only as a marker or reference to various home pages or content (like from Centers for Disease Control and Prevention (CDC), ATSDR or HHS websites; Ministry of Health and Family Welfare India (MOHFW); World Health Organization (WHO); European Centre for disease prevention and control; NHS or any other). A link does not indicate any form of endorsement or approval from any such source.
Read full disclaimer, privacy policies and terms and condition. Link provided below.
Contact if any discrepancies - "contact@sensingmedicine.com"
Discover more from Sensing Medicine
Subscribe to get the latest posts sent to your email.