Summary & Overview
CPT 84520: Blood Urea Nitrogen (BUN) Quantitative Test
CPT code 84520 represents a quantitative laboratory measurement of blood urea nitrogen (BUN), a common clinical chemistry test used to assess renal function and nitrogen balance. This test is widely ordered across inpatient and outpatient settings and carries national importance because BUN levels influence diagnostic and management decisions for kidney disease, dehydration, metabolic disturbances, and medication monitoring. Typical sites of service include hospital laboratories, independent clinical labs, and outpatient clinics with phlebotomy services. Key payers discussed include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise clinical context for the test, expected sites of service and service type, and a summary of common modifiers associated with lab billing. The publication also provides benchmarking and reimbursement context where available, coding practice considerations for laboratory services, and notes on documentation and claims processing relevant to national payers. Data not available in the input is clearly marked where applicable, including associated taxonomies, ICD-10 diagnoses, related codes, and payer-specific reimbursement rates.
Billing Code Overview
CPT code 84520 describes a laboratory test in which a laboratory analyst measures the amount of urea nitrogen in patient blood. This test is used to evaluate renal function and nitrogen balance by quantifying blood urea nitrogen (BUN).
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Service type: Clinical laboratory test — quantitative measurement of blood urea nitrogen
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Typical site of service: Hospital laboratory, independent clinical laboratory, or outpatient phlebotomy/clinic setting
Clinical & Coding Specifications
Clinical Context
A 58-year-old male with hypertension and type 2 diabetes presents to the outpatient clinic for routine monitoring and evaluation for fatigue and mild peripheral edema. The clinician orders basic metabolic laboratory panels to assess renal function and electrolyte status. As part of that panel, a serum blood urea nitrogen (BUN) test is performed. A phlebotomist collects a venous blood specimen in the clinic laboratory; the specimen is sent to the hospital core laboratory where a clinical laboratory scientist or lab analyst runs the quantitative BUN assay using automated chemistry analyzers. Results are reviewed by the ordering provider to assess renal perfusion, hydration status, and to aid interpretation of creatinine and estimated glomerular filtration rate (eGFR). Typical workflow steps: patient registration and order entry, specimen collection by phlebotomy, specimen labeling and transport to the laboratory, specimen accessioning, analysis by laboratory personnel, result verification, and result reporting to the ordering provider. Typical sites of service include outpatient clinic laboratories, hospital inpatient laboratories, and independent clinical pathology laboratories.
Coding Specifications
| Modifier | Description | When to Use |
|---|---|---|
26 | Professional component | When billing only the professional interpretation component separately (rare for automated BUN). |