HCPCS code J3370: Deleted and replaced by J3373 billing guide

Key Takeaways

HCPCS code J3370 (injection, vancomycin HCl, 500 mg) was deleted effective June 30, 2025, as part of CMS’s Q3 2025 HCPCS Level II quarterly update

The direct replacement is HCPCS code J3373 (injection, vancomycin hydrochloride, 10 mg), effective July 1, 2025, billed per 10 mg administered instead of per 500 mg

J3371 (Mylan formulation) and J3372 (Xellia formulation) were deleted the same day and replaced by J3374 and J3375, both also billed per 10 mg

Billing J3373 with the old 500 mg-per-unit math undercounts badly: a 1,000 mg dose is J3373 x 100 units, not x 2, and there is no grace period for claims still carrying the deleted J3370

Pabau’s claims management software helps outpatient infusion practices update their charge master to J3373 and flags a deleted code like J3370 before a claim goes out

If your charge master still lists HCPCS code J3370, it’s out of date. CMS deleted J3370, injection of vancomycin HCl 500 mg, effective June 30, 2025, and replaced it with HCPCS code J3373, billed per 10 mg instead of per 500 mg.

That change in unit size is the trap. A 1,000 mg dose that used to bill as 2 units of J3370 now bills as 100 units of J3373, and a claim that still carries the deleted code rejects outright rather than pending for review. IV therapy clinic workflows that handle high-volume antibiotic infusions need their charge master updated before the next vancomycin claim goes out.

HCPCS code J3370: What changed and what replaced it

HCPCS code J3370 was a Level II Healthcare Common Procedure Coding System code maintained by the Centers for Medicare and Medicaid Services, or CMS. Its descriptor was “injection, vancomycin HCl, 500 mg,” and practices used it to bill physician-administered vancomycin in outpatient and infusion settings.

CMS deleted J3370 effective June 30, 2025, in the Q3 2025 HCPCS Level II quarterly update. The replacement, HCPCS code J3373 (injection, vancomycin hydrochloride, 10 mg), took effect the next day, July 1, 2025. The drug hasn’t changed. What changed is the descriptor’s unit size, from 500 mg down to 10 mg, which is why every unit calculation built around J3370 needs to be rebuilt rather than just relabeled.

J3370 and J3373 at a glance

J3370 code status: Deleted and replaced by J3373

This is settled, not ambiguous. AAPC’s HCPCS code reference lists J3370 as a deleted code effective June 30, 2025. CGS Medicare’s update notice from July 2025, one of the Medicare Administrative Contractor (MAC) bulletins that track CMS’s quarterly code changes, confirms the same discontinue date. Verify current status against the official CMS HCPCS quarterly update file for the effective period you’re billing.

J3373 (injection, vancomycin hydrochloride, 10 mg) is the direct replacement, effective July 1, 2025. CMS’s per-code descriptor for J3370 hasn’t survived the update, but the drug it billed for has simply moved to a smaller, more granular unit size, the same pattern CMS has used elsewhere when a per-dose code gets replaced by a per-milligram one.

The same quarterly update deleted two brand-specific vancomycin codes alongside J3370: J3371 (Mylan formulation) and J3372 (Xellia formulation), both effective June 30, 2025. Their replacements, J3374 and J3375, took effect July 1, 2025, on the same 10 mg basis as J3373.

How to bill J3373: Billing units on the new 10 mg basis

Each unit of HCPCS code J3373 equals 10 mg of vancomycin hydrochloride administered, not 500 mg. Billers calculate units by dividing the total dose administered by 10, then rounding up to the nearest whole unit. Vancomycin is commonly dosed by patient weight (roughly 15 to 20 mg/kg), which produces doses that don’t always land on a round number, so the rounding step matters more here than it did under the old 500 mg descriptor.

Rounding rule: When the administered dose doesn’t divide evenly into 10 mg increments, round up to the nearest whole unit. Bill for what was actually administered, not what was ordered, and document the exact milligram figure in the medication administration record (MAR) to support the unit count on the claim.

For dates of service on or before June 30, 2025: J3370 is still the correct historical code, billed at 500 mg per unit, for claims and appeals tied to that period. Anything dated July 1, 2025 or later must use J3373 at 10 mg per unit. Claims management software that links drug administration records to billing units can catch a leftover 500-mg-based unit count before it goes out under the new code.

Related HCPCS codes: The full J3370 crosswalk

Every vancomycin HCl code in the old 500 mg series was deleted in the same update and replaced on a 10 mg basis. Review the table below before selecting a code for any vancomycin claim.

When a specific J-code exists for the drug being administered, use it in preference to J3490. The unclassified fallback needs extra documentation and frequently triggers manual review, which delays payment. J3370 isn’t the only J-code CMS has deleted and consolidated onto a per-milligram basis. HCPCS code J1040 went through the same kind of change, so treat quarterly crosswalk checks as routine billing maintenance rather than a one-time fix.

Vancomycin HCl: Drug overview and clinical context

Vancomycin hydrochloride is a glycopeptide antibiotic used to treat serious gram-positive bacterial infections, including methicillin-resistant Staphylococcus aureus (MRSA), bacteremia, endocarditis, and Clostridioides difficile. Because it requires intravenous administration, it’s routinely dispensed and billed in outpatient infusion centers, hospital outpatient departments, and physician offices with infusion suites.

Managing prescription management workflows for high-potency antibiotics like vancomycin requires careful documentation of dose, administration route, and clinical indication. The FDA has approved multiple vancomycin HCl formulations, and the HCPCS Level II code set now assigns J3373 to the generic 10 mg injection unit regardless of manufacturer brand.

• Drug class: Glycopeptide antibiotic
• Route of administration: Intravenous (IV) infusion
• Common indications: MRSA, bacteremia, endocarditis, bone and joint infections, C. difficile colitis
• Typical dose range: 500 mg to 2,000 mg per dose, often weight-based at roughly 15 to 20 mg/kg, depending on patient weight, renal function, and infection severity (the prescribing physician determines specific dosing)
• Care settings: Outpatient infusion center, hospital outpatient department, physician office infusion suite

Medicare coverage and reimbursement for HCPCS code J3373

Medicare covers vancomycin HCl injection under Part B when administered in an outpatient setting, whether a hospital department or a physician’s office running on GP clinic software, under a physician’s direct supervision. Reimbursement follows the average sales price (ASP) methodology, which the CMS Physician Fee Schedule updates quarterly. The change from J3370 to J3373 doesn’t change the payment methodology, only the unit size the ASP rate is applied to.

Average sales price (ASP) and drug pricing

Under Medicare Part B, physician-administered drugs are reimbursed at ASP+6%. In practice, the 2% Medicare sequestration reduction that’s applied to most Part B drug payments since 2013 brings the effective rate closer to ASP+4.3%. The ASP is the weighted average sales price across all manufacturers, net of rebates and other price concessions, and CMS publishes updated ASP files quarterly, typically effective January 1, April 1, July 1, and October 1 each year.

Because vancomycin is a widely manufactured generic, its ASP tends to be relatively low compared to branded biologics. Specific current dollar amounts change quarterly and per-unit rates now apply to the 10 mg unit under J3373, not the old 500 mg unit, so a historical J3370 rate can’t be reused directly. Verify against the most recent CMS ASP file for the applicable quarter.

Buy and bill: How vancomycin billing works under J3373

Buy-and-bill is the standard model for outpatient J3373 billing. Under this arrangement, the practice purchases the drug from a wholesaler, administers it to the patient, and then bills the payer for both the drug cost and the administration. IV infusion EMR systems typically need to track drug acquisition costs, lot numbers, and administered doses to support this billing model.

• Step 1: Acquire the drug. Purchase vancomycin HCl from a licensed pharmaceutical wholesaler. Document acquisition cost and NDC number.
• Step 2: Verify medical necessity. Confirm a valid ICD-10-CM diagnosis code supports the administration. Common supporting codes include A41.x (sepsis), B95.62 (MRSA infection), and I33.0 (acute infective endocarditis).
• Step 3: Administer and document. Administer the prescribed dose IV and document the exact milligram dose in the medication administration record.
• Step 4: Calculate billing units. Divide the administered dose by 10 mg to determine the number of J3373 units to bill.
• Step 5: Pair with administration code. Bill J3373 alongside the appropriate CPT administration code (e.g., 96365 for the initial infusion hour) on the same claim.
• Step 6: Submit the claim. Include the NDC number, administered quantity, and supporting diagnosis codes on the claim form.

Understanding IV therapy administration rules in your state is a prerequisite before setting up a buy-and-bill workflow. Scope-of-practice requirements vary and affect which staff members may hang the bag and document the administration. Medical office HIPAA compliance also applies to drug administration documentation, which must be maintained securely and retained per applicable state and federal retention schedules.

ICD-10 diagnosis codes supporting medical necessity

Payers require at least one ICD-10-CM diagnosis code that demonstrates medical necessity for the vancomycin administration. Without a valid, specific diagnosis code, the claim for HCPCS code J3373 will typically deny. The table below lists commonly accepted supporting diagnoses, though specific local coverage determinations (LCDs) vary by Medicare Administrative Contractor (MAC) and should be verified against current MAC policy.

Important: Always code to the highest level of specificity available. Note that A41.02 (sepsis due to MRSA) and A41.01 (sepsis due to methicillin-susceptible Staphylococcus aureus, or MSSA) describe different organisms. Confirm which one the culture and sensitivity results support before submitting.

Review your MAC’s LCD or article for vancomycin to confirm the accepted diagnosis code list in your region. Good healthcare practice documentation forms embed that diagnosis capture into the clinical workflow rather than relying on after-the-fact chart review.

Inpatient vs. outpatient billing considerations

HCPCS code J3373 applies exclusively to outpatient settings under Medicare, the same rule that applied to J3370. When vancomycin is administered to a Medicare patient during an inpatient hospital admission, the drug cost is bundled into the Diagnosis-Related Group (DRG) payment. Submitting J3373 separately for an inpatient admission is a billing compliance error.

Outpatient parenteral antibiotic therapy (OPAT) is the most common clinical scenario for J3373 in independent infusion settings. Patients discharged from the hospital with a continuing IV antibiotic regimen receive their remaining doses at an outpatient infusion center, where J3373 is correctly billed under Part B. Some OPAT patients instead continue treatment through home health services, a setting with its own certification requirements like HCPCS code G0180.

For practices setting up an infusion program, opening an infusion clinic covers the operational and compliance requirements.

Streamline your infusion billing workflow

Pabau helps outpatient infusion practices and physician offices link drug administration records directly to HCPCS claims, reducing unit calculation errors and missed documentation before submission, including catching a deleted code like J3370 before it goes out.

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Common billing errors when transitioning from J3370 to J3373

The switch from a 500 mg descriptor to a 10 mg one is exactly the kind of change that trips up a manual billing process. The table below covers the errors that show up most often during this transition.

Documentation requirements for J3373 claims

Documentation is where J3373 claims succeed or fail at audit. Keep the following in the patient record for every vancomycin administration:

• Exact mg dose administered: Needed to calculate the correct J3373 unit count; the vial size ordered isn’t sufficient on its own.
• Route and setting: IV infusion, and the care setting (office, hospital outpatient department, independent infusion center).
• Diagnosis supporting medical necessity: The specific ICD-10-CM code, matched to the actual organism and site where the code set requires it.
• NDC number: Required on Medicare Part B drug claims, and mandatory if a claim is ever routed through J3490.
• Prescribing and administering provider: Name and NPI, particularly in multi-provider infusion practices.

Pair this documentation with the vital signs recorded during the infusion, since a clear timestamp trail supports both patient safety and the claim if it’s ever audited. A vital signs record template keeps that log consistent across staff and shifts.

Where to verify J3373’s status and payment rate

• CMS HCPCS Quarterly Update page: The primary source confirming J3370’s deletion, J3373’s effective date, and any further changes.
• CMS Medicare Part B Drug ASP Pricing files: Confirms the current per-10-mg payment rate for J3373, updated quarterly.
• AAPC HCPCS code database: Lists J3373’s descriptor and confirms J3370, J3371, and J3372 as deleted codes.
• Your MAC’s website: CGS, Noridian, Palmetto GBA, and other MACs publish LCDs and billing update notices specifying documentation requirements for J3373 claims in your jurisdiction.

Conclusion

HCPCS code J3370 is gone: deleted effective June 30, 2025, and replaced by J3373, billed per 10 mg administered rather than per 500 mg. Getting this right depends on three things: updating the charge master so no claim still carries J3370, J3371, or J3372, rebuilding the unit calculation around the 10 mg basis rather than 500 mg, and pairing J3373 with a valid, organism-specific ICD-10-CM diagnosis.

Pabau’s claims management software helps outpatient infusion practices and physician offices link drug administration documentation directly to HCPCS billing records, flagging a deleted code like J3370 and a stale unit count before either one leaves the practice. To see how Pabau handles drug billing workflows in practice, book a demo.

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