Blood Urea Nitrogen (BUN)
Clinical interpretation, reference ranges, and BUN/Creatinine ratio evaluation under KDIGO 2024 standards.
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Quick Reference Facts
Laboratory Interpretation Workflow
1. Clinical Indication
Ordering protocols based on clinical indications, presenting symptoms, or screening guidelines.
Clinical Pearl: Order when screening for primary organ dysfunctions or monitoring active treatment efficacy.
Test Description & Overview
Blood Urea Nitrogen (BUN): Biochemical measurement of nitrogen in the form of urea, the primary waste product of hepatic protein catabolism, cleared by glomerular filtration and variable passive renal tubular reabsorption dependent on hydration state.
Adults: 7 - 20 mg/dL (2.5 - 7.1 mmol/L); BUN/Creatinine Ratio: 10:1 to 20:1.
Elevated (High) Values
- Prerenal Azotemia (BUN/Creatinine >20:1): Dehydration, Gastrointestinal Hemorrhage, High Protein Diet
- Intrinsic Renal Failure (BUN/Creatinine 10:1 to 15:1): Glomerulonephritis, Acute Tubular Necrosis
- Postrenal Azotemia (BUN/Creatinine >20:1): Urinary Tract Obstruction
Decreased (Low) Values
- Severe Hepatic Failure (Impaired Urea Synthesis)
- Malnutrition, Protein Starvation, or Syndrome of Inappropriate ADH (SIADH)
- Normal Pregnancy (Plasma Volume Expansion and Increased eGFR)
Clinical Alignment & Significance
Elevated BUN >80-100 mg/dL accompanied by uremic flap (asterixis), pericardial friction rub, or lethargy indicates Uremic Syndrome demanding urgent hemodialysis.
Diagnostic Guidance Notice
Standard laboratory reference ranges vary based on the testing facility. Significant deviations require immediate clinician review to rule out severe medical pathology.
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Reference Citations & Evidence Sources
Clinical Guidelines & Consensus Statements
Clinical Reviews & Textbooks
- CIT-0023National Center for Complementary and Integrative Health. "Homeopathy: What You Need To Know." National Institutes of Health (2021).
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L0018Dr. Narayan Jethwani. "Blood Urea Nitrogen (BUN)." Homeo Healthcare Clinical Platform. Version 1.1.0. Reviewed: 2026-07-31T19:50:00Z. Available at: https://homeo.healthcare/knowledge/lab-tests/blood-urea-nitrogen
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