Summary & Overview
HCPCS C9473: Injection, mepolizumab, 1 mg
HCPCS Level II code C9473 denotes mepolizumab billed per 1 mg for injectable administration, a biologic therapy used in certain eosinophilic and allergic conditions. Nationally, precise per-milligram billing codes like C9473 matter because they affect how high-cost biologic drugs are itemized, reimbursed, and tracked across outpatient settings. This influences provider billing accuracy, insurer coverage determinations, and patient cost-sharing calculations.
Key payers in this analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find an overview of coverage considerations and administrative benchmarks tied to per-milligram HCPCS billing, plus clinical context for mepolizumab as an injectable monoclonal antibody administered in outpatient infusion or office settings. The publication outlines typical billing practice implications, payer coverage patterns, and areas where policy updates or coding guidance may affect reimbursement and reporting. It does not provide clinical guidance or individualized recommendations. Data not available in the input for specific modifiers, taxonomies, ICD-10 pairings, related codes, payer-specific reimbursement rates, or service-line details.
Billing Code Overview
HCPCS Level II code C9473 represents Injection, mepolizumab, 1 mg. This code applies to the drug product mepolizumab billed per milligram for injectable administration. The service type is medication administration of a biologic monoclonal antibody given by injection. The typical site of service is outpatient settings such as infusion centers, physician offices, or hospital outpatient departments where injectable biologic therapies are administered.
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Clinical & Coding Specifications
Clinical Context
A typical patient is an adult or adolescent with severe eosinophilic asthma or an eosinophilic phenotype of chronic rhinosinusitis with nasal polyps who presents to an outpatient infusion/injection clinic or specialty office for biologic therapy. The patient has already been evaluated by a pulmonologist, allergist/immunologist, or ENT specialist, meets clinical criteria for anti–IL-5 therapy, and has a documented recent exacerbation history or elevated blood eosinophil count. Prior to administration, a nurse verifies patient identity, obtains informed consent, reviews recent vitals and allergy history, and confirms any required prior authorization and medication lot/expiration. The provider performs a focused assessment, documents indication and baseline status, and orders the subcutaneous injection of mepolizumab dosed per prescription. After injection, the patient is monitored for 15–30 minutes for hypersensitivity or injection‑related reactions; post‑administration vitals and tolerance are documented. Billing uses HCPCS Level II code C9473 to report the medication quantity (per mg) along with appropriate visit or administration CPT codes in the clinical workflow. Common payors for authorization and reimbursement include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, BUCA, and Medicare.
Coding Specifications
| Modifier | Description | When to Use |
|---|---|---|
25 | Significant, separately identifiable evaluation and management service by the same physician on the day of the procedure |