No. Q9998 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 Q9998?

CMS's ASP crosswalk for October 1, 2026 through December 31, 2026 lists 8 NDCs under Q9998, for Selarsdi and Ustekinumab-AEKN. The table on this page shows each one with its billing units per package.

What is the Medicare payment limit for Q9998?

$10.48 per 1 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 Q9998?

One unit of Q9998 is 1 mg, as stated in the code's descriptor. Units to report = dose given ÷ 1 mg.

Q9998 HCPCS Code: Selarsdi (ustekinumab-aekn)

In short

Q9998 is the HCPCS Level II code for injection, ustekinumab-aekn (selarsdi), biosimilar, 1 mg. CMS assigns NDCs for Selarsdi and Ustekinumab-AEKN to it. One billing unit is 1 mg. The Medicare Part B payment limit is $10.48 per unit (October 1, 2026 through December 31, 2026).

Code

CMS HCPCS file

HCPCS codeQ9998

Billing unit1 mg

Descriptor: Injection, ustekinumab-aekn (selarsdi), biosimilar, 1 mg
Short descriptor: Inj ustekinumab-aekn, 1 mg
Code set: HCPCS Level II, maintained by CMS
Effective: Jul 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$10.48

Per1 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: "lesser of" methodology 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 ÷ 1 mg. For example, 100 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 = 1 mg)

Modifier

NDC (11-digit)

NDC unit qualifier

NDC quantity

Enter the dose given to build the claim line.

NDCs billed under Q9998

CMS’s ASP NDC–HCPCS crosswalk (effective October 1, 2026 through December 31, 2026) assigns 8 NDCs to Q9998 for Selarsdi and Ustekinumab-AEKN. Billing units per package are CMS’s figures for this code’s unit.

NDCs assigned to Q9998 in the CMS ASP crosswalk
Drug	NDC (11-digit)	Labeler	Package	Billing units per package
Selarsdi	51759-0505-13	Nupathe Inc	0.5	45
Selarsdi	51759-0505-32	Nupathe Inc	0.5	45
Selarsdi	51759-0607-32	Nupathe Inc	1	90
Selarsdi	51759-0708-13	Nupathe Inc	26	130
Ustekinumab-AEKN	51759-0413-32	Nupathe Inc	0.5	45
Ustekinumab-AEKN	51759-0414-32	Nupathe Inc	1	90
Ustekinumab-AEKN	51759-0709-32	Nupathe Inc	0.5	45
Ustekinumab-AEKN	51759-0710-32	Nupathe Inc	1	90

Q9998: common questions

Is Q9998 a CPT code?: No. Q9998 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 Q9998?: CMS's ASP crosswalk for October 1, 2026 through December 31, 2026 lists 8 NDCs under Q9998, for Selarsdi and Ustekinumab-AEKN. The table on this page shows each one with its billing units per package.
What is the Medicare payment limit for Q9998?: $10.48 per 1 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 Q9998?: One unit of Q9998 is 1 mg, as stated in the code's descriptor. Units to report = dose given ÷ 1 mg. J-code billing units.

Q9998 — Injection, ustekinumab-aekn (selarsdi), biosimilar, 1 mg