Summary & Overview
CPT 82140: Ammonia Measurement in Blood or Plasma
CPT code 82140 represents a clinical laboratory assay that measures ammonia levels in blood, plasma, or other body fluids. Elevated ammonia can signal metabolic derangements, liver dysfunction, or infectious processes and often prompts further diagnostic evaluation or clinical intervention. Nationally, this test is commonly ordered in emergency, inpatient, and outpatient settings where altered mental status, hepatic disease, or suspected inborn errors of metabolism are evaluated.
Payers covered in this analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. The publication provides a clear overview of clinical context, typical sites of service, and payer coverage considerations for 82140.
Readers will learn practical benchmarks and patterns relevant to 82140: common clinical indications, expected sites of service, considerations for laboratory processing and turnaround, and how major payers and Medicare typically frame coverage for ammonia testing. The summary also flags where input data is not provided and points to where readers can find policy updates, coding guidance, and typical modifier usage in detailed sections. This material is intended for clinical lab managers, billing professionals, and policy analysts seeking concise national-level context for CPT code 82140.
Billing Code Overview
CPT code 82140 describes a laboratory measurement of ammonia in blood, plasma, or other body fluids. This test detects elevated ammonia levels, which can be indicative of metabolic disturbances, hepatic dysfunction, or infectious processes affecting nitrogen metabolism.
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Service type: Clinical laboratory diagnostic test measuring ammonia concentration in biological fluids
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Typical site of service: Hospital laboratory, independent clinical laboratory, or inpatient/outpatient blood-draw locations
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Clinical & Coding Specifications
Clinical Context
A typical patient is a hospitalized adult or pediatric patient presenting with altered mental status, unexplained encephalopathy, suspected hepatic failure, inborn errors of metabolism, or recent severe infection/sepsis. The clinician orders an ammonia measurement (82140) when hyperammonemia is suspected to evaluate for hepatic dysfunction, portosystemic shunting, urea cycle disorder, or metabolic decompensation. Blood (usually plasma collected on ice and delivered rapidly to the lab) or other body fluids are obtained by phlebotomy; the specimen is processed in the clinical laboratory where an automated analyzer or enzymatic assay measures ammonia concentration. Results are reported to the ordering provider for correlation with liver function tests, venous/arterial blood gases, lactate, and clinical exam to guide diagnostic evaluation and acute management decisions. Typical sites of service include hospital inpatient wards, emergency departments, intensive care units, and specialty clinics (e.g., hepatology, metabolic disorders clinic).
Coding Specifications
| Modifier | Description | When to Use |
|---|---|---|
26 | Professional component | Use when only the professional interpretation/report of the laboratory test is billed separately (rare for standalone lab tests). |