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BUN (Blood Urea Nitrogen) Test
✅ Up to date🔬 Evidence: ModerateInternal Medicine
Diğer adları: Blood urea nitrogen, BUN, Urea nitrogen
⚠️
Discuss your test results with your doctor. This page is for informational purposes only and does not provide a diagnosis.
⚡ Key Facts
• An end product of protein metabolism, produced by the liver and excreted by the kidneys
• More influenced by non-renal factors than creatinine
• BUN/creatinine ratio provides additional diagnostic information
• Used alongside creatinine and eGFR for kidney assessment
🧪 What Does This Test Measure?
The BUN test measures blood urea nitrogen, an end product of protein metabolism produced by the liver and excreted by the kidneys.
📋 Why Is It Ordered?
Ordered alongside creatinine for kidney function assessment, dehydration evaluation, BUN/creatinine ratio calculation, and GI bleeding investigation.
🔧 Preparation
The BUN test generally requires no special preparation. However, high-protein meals can significantly elevate urea levels.
📊 Reference Ranges
Commonly used reference ranges:
BUN: 7–20 mg/dL (2.5–7.1 mmol/L)
BUN/Creatinine ratio: approximately 10–20:1
⚠️ Reference ranges may vary by laboratory.
⬆️ High Values
Elevated BUN may be associated with decreased kidney function, dehydration, high protein intake, GI bleeding, heart failure, catabolic states, or certain medications.
⬇️ Low Values
Low BUN generally does not cause serious clinical concern. It may be associated with low protein intake, severe liver disease, pregnancy, or overhydration.
⚙️ What Can Affect Results?
Protein intake, hydration status, liver function, GI bleeding, catabolic state, age, and certain medications may affect BUN levels.
🔬 Evidence Summary
Moderate evidence: 1 guideline, 2 landmark observational studies.
✅ Key Takeaways
💡
What you learned: BUN is influenced by both kidney function and non-renal factors like protein intake and hydration. It is most informative when evaluated alongside creatinine and eGFR.
⛔
A BUN result alone cannot diagnose kidney disease. Creatinine, eGFR, and clinical context are needed.
🔬 Sources Used on This Page
3 sources · Most recent publication: 2024📋
Guideline
Expert society and guideline recommendations
1
source
👁
Observational
Observational and cohort studies
2
sources
Overall assessment: Evidence level for this topic is moderate. This page is supported by 1 guideline, 2 observational studies.
📝 Questions to Ask Your Doctor
Be prepared for your appointment. Add questions to your list.
Last reviewed: 4/1/2026
Next review: 7/1/2026
🔗 Related Topics
🩺 Chronic kidney disease🧪 Creatinine🧪 eGFR (tahmini glomerüler filtrasyon hızı)🧪 ALT/AST (karaciğer fonksiyon bağlamı)
⚖️ This page does not replace medical advice. Make treatment decisions with your doctor.
Content is based on scientific studies indexed in PubMed and current clinical guidelines.
Content is based on scientific studies indexed in PubMed and current clinical guidelines.