HCPCS code J9145: Injection, daratumumab, 10 mg billing guide

Key Takeaways

HCPCS code J9145 describes Injection, daratumumab, 10 mg; 1 billable unit equals 10 mg of drug administered.

Use J9145 for IV daratumumab (Darzalex); use J9144 for the subcutaneous Darzalex Faspro formulation with hyaluronidase-fihj.

JW and JZ modifiers are required on all J9145 claims effective July 1, 2023, to report drug waste or confirm zero waste.

Pabau’s claims management software helps oncology billing teams track chemotherapy drug units, modifiers, and payer authorizations in one place.

HCPCS code J9145 is the billing code for Injection, daratumumab, 10 mg — a CD38-targeting monoclonal antibody infused intravenously to treat multiple myeloma. Each 10 mg administered equals one billable unit, and claims must include the correct unit count, NDC, JW or JZ modifier, and a covered ICD-10-CM diagnosis. This guide covers every element required for clean J9145 claim submission, from dosage calculations and modifier rules to prior authorization and reimbursement methodology.

HCPCS code J9145: Description and properties

HCPCS code J9145 describes Injection, daratumumab, 10 mg. Every 10 mg of daratumumab administered equals one billable unit — a 100 mg infusion = 10 units on the claim. The most common denial reason for J9145 is a unit calculation error: billing one unit when the patient received 100 mg, rather than the correct 10 units.

J9145 falls within the HCPCS Level II Chemotherapy Drugs range (J9000–J9999), maintained by the Centers for Medicare and Medicaid Services (CMS). The code has been active since January 1, 2017, with a Coverage Code of D, meaning special coverage instructions apply, and an Action Code of N, confirming no ongoing maintenance updates are scheduled.

Daratumumab is a CD38-targeting monoclonal antibody used primarily to treat multiple myeloma. Janssen Pharmaceuticals (a Johnson & Johnson company) manufactures and markets it under the brand name Darzalex. Because it falls in the J9000–J9999 chemotherapy drug range, claims management software that tracks oncology-specific billing rules is essential for practices administering this drug.

J9145 dosage units and billing calculation

Daratumumab dosing is weight-based. Patients typically receive 16 mg/kg per infusion, so a 70 kg patient receives 1,120 mg. That translates to 112 units on the J9145 claim line. Miscounting by even one unit creates a discrepancy that payers flag for review.

First Coast Service Options (FCSO) Medicare guidance confirms the calculation explicitly: J9145 with 10 units = 100 mg administered.

Step-by-step unit calculation

1. Confirm the total milligrams administered (from the infusion record or nursing note).
2. Divide total mg by 10 to get billable units. Example: 800 mg divided by 10 = 80 units.
3. Round down if the dispensed amount does not divide evenly; report the administered amount, not the vial size.
4. Record any unused drug from opened vials separately using the JW modifier (see below).
5. Enter the unit count in Box 24G (professional claim) or Form Locator 46 (institutional claim).

Correct unit reporting depends on an accurate infusion record, the same discipline that underpins home infusion therapy billing. If the record does not capture the precise administered dose, the unit count cannot be verified.

J9145 vs. J9144: Choosing the right daratumumab code

Two HCPCS codes describe daratumumab. Using the wrong one triggers an immediate denial.

J9144 covers Darzalex Faspro, the subcutaneous co-formulation that combines daratumumab with hyaluronidase-fihj. Because the two products differ in route, dose, and vial size, they are not interchangeable on a claim. Always verify the order against the administered product before selecting the code.

An oncology billing team that regularly manages both formulations benefits from a system that pulls the dispensed product automatically into the claim, reducing the manual lookup that causes code-selection errors — the same safeguard that helps with adjacent oncology injectables like decitabine injection billing.

NDC numbers for J9145

CMS requires National Drug Code (NDC) reporting on most Part B drug claims. For J9145, the dispensed vial’s NDC must appear in the 11-digit 5-4-2 format on the claim. Submitting with the wrong format or an outdated NDC is a common reason for secondary edits and delayed payment.

Verified 11-digit NDC numbers for Darzalex 100 mg/5 mL single-dose vials, per the official Janssen/J&J reimbursement guide, include:

• 57894-0502-05 (Darzalex 100 mg/5 mL single-dose vial)
• 57894-0505-05 (Darzalex 100 mg/5 mL single-dose vial)

Always confirm the NDC from the dispensed vial label before claim submission; it must match exactly what was administered. For professional claims, the NDC goes in Item 24D alongside the HCPCS code J9145. On institutional claims, use Form Locator 44.

Maintaining accurate drug inventory records that link dispensed NDCs to patient encounters is part of solid billing compliance across every injectable code — including biosimilar codes like infliximab-axxq (Avsola) billing. Discrepancies between dispensing records and claim-line NDCs can trigger payer audits.

JW and JZ modifiers for J9145

CMS made JW/JZ modifier reporting mandatory effective July 1, 2023. Every J9145 claim must include one of these two modifiers. Omitting both is now a claim-level error under Medicare policy.

J9145 is included in the CMS JW/JZ Modifier Policy HCPCS Codes document, confirming that waste billing applies. Darzalex comes as a single-dose vial. In practice, when a patient’s weight-based dose does not consume the entire vial contents, the remainder must be reported on a separate claim line with modifier JW.

JW modifier billing example

A patient’s weight-based dose is 880 mg of daratumumab. The practice draws eight full 100 mg vials (800 mg) and opens a ninth vial, administering 80 mg from it and discarding the remaining 20 mg.

• Line 1: J9145, 88 units (880 mg administered, no modifier needed for the administered amount)
• Line 2: J9145, 2 units (20 mg discarded), modifier JW

Submit both lines on the same claim. The JW line documents the waste and allows Medicare to reimburse for it under the single-dose vial policy. Skipping the JW line means the practice absorbs the cost of wasted drug with no reimbursement.

Tracking open vials and waste per patient encounter is easier when your practice captures administered versus dispensed amounts at the point of care. Manual paper logs introduce the transcription errors that cause JW/JZ omissions.

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Medicare and commercial payer reimbursement

Medicare Part B reimburses separately billed drugs like daratumumab using the Average Sales Price (ASP) plus 6% methodology. The West Virginia Bureau for Medical Services fee schedule (effective October 1 through December 31, 2025) lists J9145 at $71.371 per 10 mg unit. For a 1,000 mg infusion (100 units), that amounts to approximately $7,137 before any cost-sharing.

CMS updates ASP-based reimbursement quarterly, so the applicable rate depends on the date of service. Always check the current CMS Physician Fee Schedule lookup or the quarterly ASP drug pricing file for the period covering the infusion date.

Reimbursement methodology comparison

Commercial insurers set their own rates for J9145. Most large payers reimburse at a percentage of AWP or at contracted rates negotiated with the practice or infusion center.

Site-of-service affects payment: hospital outpatient departments typically receive higher reimbursement under the Outpatient Prospective Payment System (OPPS) than physician office settings under the Physician Fee Schedule. Verify your contracted rate for each payer before patient scheduling, since the difference can run into thousands of dollars per infusion.

For practices managing revenue across multiple payer contracts, centralizing reimbursement tracking in dedicated medical billing software reduces the risk of billing at the wrong rate for the wrong payer.

ICD-10 diagnosis codes used with J9145

Payers require a covered diagnosis on every J9145 claim line. Daratumumab is FDA-approved for multiple myeloma indications, and the diagnosis code submitted must match the documented indication in the patient record.

Coverage can still vary by payer Local Coverage Determination (LCD), so always confirm the covered diagnosis directly with your MAC or payer before billing. Document medical necessity explicitly in the patient record to support the claim.

Linking diagnosis documentation to claim submission maintains a clear audit trail from clinical note to claim line. That discipline carries over to the supportive-care drugs myeloma patients often receive alongside daratumumab, such as zoledronic acid.

Prior authorization for J9145

Prior authorization requirements for J9145 vary by payer and plan. Most commercial payers and Medicare Advantage plans require prior authorization before the first daratumumab infusion, with re-authorization required for subsequent treatment lines.

Traditional Medicare Part B does not require prior authorization for J9145 under fee-for-service, but individual Medicare Administrative Contractors (MACs) may have additional documentation requirements through Local Coverage Determinations. Medicaid programs vary by state: some require authorization for every cycle, others for the initial cycle only.

What payers typically require for authorization

• Confirmed ICD-10 diagnosis of multiple myeloma with pathology or bone marrow biopsy documentation
• Prior treatment history (number of prior lines, specific agents used)
• ECOG or Karnofsky performance status from the treating oncologist
• Prescribing physician’s specialty (oncology or hematology typically required)
• Planned treatment regimen (daratumumab monotherapy vs. combination; cycle frequency)

Maintaining structured prior authorization documentation is part of broader compliance management for practices handling specialty infusion drugs. Missing one document in the authorization packet is enough to trigger a denial that takes weeks to appeal.

Infusion administration codes for J9145

J9145 covers the drug cost only. The infusion service requires separate CPT codes, and payers expect both on the same claim.

Daratumumab infusions typically run 3.5 to 7 hours for the initial infusion (longer for first administration due to infusion reaction monitoring). Subsequent infusions may be shorter if the patient tolerates the drug well. Bill 96413 for the first hour and 96415 for each additional hour, rounded to the nearest hour per CMS guidance.

Pre-medications such as antihistamines, corticosteroids, and antiemetics like granisetron given before the infusion may be separately billable depending on the payer. Verify whether your MAC or commercial payer allows separate billing for pre-medications alongside J9145.

Practices managing complex infusion procedure billing across multiple drug codes benefit from templates that standardize which administration codes accompany each drug HCPCS code.

Related HCPCS codes and crosswalk

Oncology billing teams encounter several codes adjacent to J9145. Knowing when each applies prevents miscoding and inadvertent upcoding.

C9476 is listed as a related transitional outpatient code for daratumumab 10 mg. Transitional codes are assigned by CMS when a product lacks a permanent HCPCS code; they are typically replaced or retired. Verify the current status of C9476 with your Medicare Administrative Contractor before using it, as transitional codes have limited active windows.

For practices that also handle other monoclonal antibody injectables — such as durvalumab, ocrelizumab, or ublituximab — maintaining a structured crosswalk between drugs, HCPCS codes, and administration CPT codes keeps billing compliant. Cross-referencing drug orders against HCPCS assignments before claim generation catches mis-mapping before it reaches the payer.

Claim submission checklist for J9145

A complete J9145 claim requires each of these elements. Missing any one of them causes a delay, denial, or edit request.

• Code: J9145 in the HCPCS field (Item 24D for CMS-1500 / Form Locator 44 for UB-04)
• Units: Total mg administered divided by 10, entered as whole units
• NDC: 11-digit NDC in 5-4-2 format from the dispensed vial label
• Modifier: JW (drug waste reported) or JZ (no waste) on every claim line
• Diagnosis: Covered ICD-10-CM code documented in the medical record
• Administration code: CPT 96413 for the first hour; 96415 for additional hours
• Authorization number: Prior authorization reference where required by the payer
• Date of service: Exact infusion date (not the order date or prescription date)

Running a pre-submission audit against this checklist for every J9145 claim reduces first-pass denial rates. Practices with high chemotherapy volumes often build this checklist into their billing workflow using structured documents like a superbill.

Linking it to your paperless practice documentation system means the administered dose, NDC, and waste data flow directly into the claim rather than being re-entered manually.

Key billing rules for HCPCS code J9145

Daratumumab billing errors almost always trace back to three points: wrong unit count, missing modifier, or mismatched diagnosis code. J9145 is specific to IV daratumumab at 10 mg per unit, and every claim must include the correct units, NDC, JW or JZ modifier, and a covered ICD-10-CM diagnosis.

Pabau’s claims management software gives oncology and infusion practices a structured environment for tracking drug units, modifiers, and payer authorizations without relying on disconnected spreadsheets. If your team is managing J9145 claims alongside other specialty infusion codes, book a demo to see how Pabau handles the J9145 billing workflow from encounter to claim.

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