No. J2291 is a HCPCS Level II code, maintained by CMS, that identifies the drug supplied. CPT codes are five-digit numbers from the AMA that describe services. Giving the drug, for example an injection or infusion, is usually reported with a separate CPT administration code.

What NDCs are billed under J2291?

CMS's ASP crosswalk for October 1, 2026 through December 31, 2026 lists 2 NDCs under J2291, for Nafcillin. The table on this page shows each one with its billing units per package.

What is the Medicare payment limit for J2291?

$0.135 per 20 mg, effective October 1, 2026 through December 31, 2026, from CMS's Part B drug payment limit file. Multiply by the units billed for the allowed amount before deductible and coinsurance. It is not a coverage decision.

What is one billing unit of J2291?

One unit of J2291 is 20 mg, as stated in the code's descriptor. Units to report = dose given ÷ 20 mg.

J2291 J-Code: Nafcillin sodium — Billing Units & NDCs

In short

J2291 is the HCPCS Level II code for injection, nafcillin sodium (baxter), 20 mg. CMS assigns NDCs for Nafcillin to it. One billing unit is 20 mg. The Medicare Part B payment limit is $0.135 per unit (October 1, 2026 through December 31, 2026).

Code

CMS HCPCS file

HCPCS codeJ2291

Billing unit20 mg

Descriptor: Injection, nafcillin sodium (baxter), 20 mg
Short descriptor: Inj, nafcillin (baxter) 20mg
Code set: HCPCS Level II, maintained by CMS
Effective: Oct 1, 2025

The billing unit is read from the descriptor. Confirm it against the CMS file before billing.

Medicare Part B payment limit

CMS ASP file

Payment limit per unit$0.135

Per20 mg

Coinsurance20%

Effective October 1, 2026 through December 31, 2026. Payment allowance limits subject to the ASP methodology are based on 2Q26 ASP data. A payment limit is not a coverage decision; the Medicare contractor decides coverage. CMS ASP pricing files

Units and claim line

Units = dose given ÷ 20 mg. For example, 2000 mg is 100 units. Enter the dose to get the units and the NDC line for the CMS-1500 and the 837P.

Dose given (mg)

HCPCS units (1 unit = 20 mg)

Modifier

NDC (11-digit)

NDC unit qualifier

NDC quantity

Enter the dose given to build the claim line.

NDCs billed under J2291

CMS’s ASP NDC–HCPCS crosswalk (effective October 1, 2026 through December 31, 2026) assigns 2 NDCs to J2291 for Nafcillin. Billing units per package are CMS’s figures for this code’s unit.

NDCs assigned to J2291 in the CMS ASP crosswalk
Drug	NDC (11-digit)	Labeler	Package	Billing units per package
Nafcillin	00338-1017-41	Baxter Healthcare Corporation	50	50
Nafcillin	00338-1019-48	Baxter Healthcare Corporation	100	100

J2291: common questions

Is J2291 a CPT code?: No. J2291 is a HCPCS Level II code, maintained by CMS, that identifies the drug supplied. CPT codes are five-digit numbers from the AMA that describe services. Giving the drug, for example an injection or infusion, is usually reported with a separate CPT administration code. CPT codes for drug administration.
What NDCs are billed under J2291?: CMS's ASP crosswalk for October 1, 2026 through December 31, 2026 lists 2 NDCs under J2291, for Nafcillin. The table on this page shows each one with its billing units per package.
What is the Medicare payment limit for J2291?: $0.135 per 20 mg, effective October 1, 2026 through December 31, 2026, from CMS's Part B drug payment limit file. Multiply by the units billed for the allowed amount before deductible and coinsurance. It is not a coverage decision.
What is one billing unit of J2291?: One unit of J2291 is 20 mg, as stated in the code's descriptor. Units to report = dose given ÷ 20 mg. J-code billing units.

J2291 — Injection, nafcillin sodium (baxter), 20 mg