No. Q5123 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 Q5123?

CMS's ASP crosswalk for October 1, 2026 through December 31, 2026 lists 2 NDCs under Q5123, for Riabni. The table on this page shows each one with its billing units per package.

What is the Medicare payment limit for Q5123?

$21.083 per 10 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 Q5123?

One unit of Q5123 is 10 mg, as stated in the code's descriptor. Units to report = dose given ÷ 10 mg.

Q5123 HCPCS Code: Riabni (rituximab-arrx) — Billing Units

In short

Q5123 is the HCPCS Level II code for injection, rituximab-arrx, biosimilar, (riabni), 10 mg. CMS assigns NDCs for Riabni to it. One billing unit is 10 mg. The Medicare Part B payment limit is $21.083 per unit (October 1, 2026 through December 31, 2026).

Code

CMS HCPCS file

HCPCS codeQ5123

Billing unit10 mg

Descriptor: Injection, rituximab-arrx, biosimilar, (riabni), 10 mg
Short descriptor: Inj. riabni, 10 mg
Code set: HCPCS Level II, maintained by CMS
Effective: Jul 1, 2021

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$21.083

Per10 mg

Coinsurance20%

Effective October 1, 2026 through December 31, 2026. Payment allowance limits subject to the ASP methodology are based on 2Q26 ASP data. CMS note: 8% of reference add-on applied. A payment limit is not a coverage decision; the Medicare contractor decides coverage. CMS ASP pricing files

Units and claim line

Units = dose given ÷ 10 mg. For example, 1000 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 = 10 mg)

Modifier

NDC (11-digit)

NDC unit qualifier

NDC quantity

Enter the dose given to build the claim line.

NDCs billed under Q5123

CMS’s ASP NDC–HCPCS crosswalk (effective October 1, 2026 through December 31, 2026) assigns 2 NDCs to Q5123 for Riabni. Billing units per package are CMS’s figures for this code’s unit.

NDCs assigned to Q5123 in the CMS ASP crosswalk
Drug	NDC (11-digit)	Labeler	Package	Billing units per package
Riabni	55513-0224-01	Amgen Inc	10	10
Riabni	55513-0326-01	Amgen Inc	50	50

Q5123: common questions

Is Q5123 a CPT code?: No. Q5123 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 Q5123?: CMS's ASP crosswalk for October 1, 2026 through December 31, 2026 lists 2 NDCs under Q5123, for Riabni. The table on this page shows each one with its billing units per package.
What is the Medicare payment limit for Q5123?: $21.083 per 10 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 Q5123?: One unit of Q5123 is 10 mg, as stated in the code's descriptor. Units to report = dose given ÷ 10 mg. J-code billing units.

Q5123 — Injection, rituximab-arrx, biosimilar, (riabni), 10 mg