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HCPCS A9591 · Level II · Part B drug

A9591: fluoroestradiol f 18, HCPCS Level II drug code

Compiled from CMS files by the QuickIntell RCM Editorial Team · Data effective · Method: reference methodology · Report a data correction

Data currency: OPPS Addendum B: October 2026 (effective October 1, 2026); OPPS NDC-HCPCS crosswalk: October 2026 (effective October 1, 2026); NCCI MUE tables: 2026 Q4 (effective October 1, 2026); NCCI PTP edits: v323r0 (2026 Q4) (effective October 1, 2026); ASC Addendum BB (covered ancillary services): October 2026 (effective October 1, 2026). Next CMS release: January 1, 2027 (quarterly update).

Key facts for A9591

Billing unit
1 millicurie
Fluoroestradiol f 18
OPPS payment rate
$460.42
no ASP limit; SI K, October 2026
Practitioner MUE
6
MAI 3
OPPS status
SI K
APC 9370
NCCI exposure
no PTP pairs
Coverage articles
0
none list this code

TL;DR

HCPCS A9591 is the Level II code for Fluoroestradiol f 18, diagnostic, 1 millicurie, billed per 1 millicurie. CMS publishes no ASP payment limit for it; hospital outpatient departments are paid separately under OPPS (status indicator K, $460.42 per billing unit in October 2026). The practitioner MUE allows up to 6 units per date of service (MAI 3). Unlike most diagnostic agents, which OPPS packages into the procedure (status N), A9591 is paid separately in the hospital outpatient department (status K). No current Billing and Coding Article lists A9591, so coverage follows the FDA label, compendia and any applicable NCD.

Medicare payment: OPPS rate (no ASP limit)

A9591 does not appear in the October 2026 Part B ASP payment limit file. CMS pays it separately to hospital outpatient departments under OPPS with status indicator K in APC 9370, at a national unadjusted rate of $460.42 per 1 millicurie. Status K is a separately paid, non-pass-through drug or biological, including therapeutic radiopharmaceuticals. In a physician office the Medicare contractor prices the drug, often from invoice; commercial and Medicaid payers set their own rates.

NDC to HCPCS billing-unit conversion

The October 2026 OPPS crosswalk lists no NDC for A9591. Report the NDC from the product label and confirm the units conversion from the HCPCS descriptor (Fluoroestradiol f 18, diagnostic, 1 millicurie).

Medically Unlikely Edits (MUE)

CMS publishes 2 MUE values for A9591. For practitioners the limit is 6 units per date of service with adjudication indicator 3, a date-of-service clinical edit: units above the limit deny but can be paid on appeal with documentation that the quantity was medically reasonable.

MUE values for A9591 by setting
SettingMUE (units/DOS)MAICMS rationale
Practitioner services63 Date of Service Edit: ClinicalPrescribing Information
Facility outpatient hospital63 Date of Service Edit: ClinicalPrescribing Information

MUE for A9591 in every setting opens the lookup with this code filled in, next to any other code on the same claim.

NCCI edits and add-on relationships

No active practitioner PTP pair lists A9591 as a column-1 or column-2 code in v323r0. Drug supply codes are rarely bundled; the administration codes billed with them are where PTP edits usually apply.

The counts above are exposure, not answers for a specific claim. Check A9591 against another code to see whether a given pair bundles, which code is paid and whether a modifier can separate them.

A9591 is neither an add-on code nor a designated primary code in the 2026 Q4 NCCI add-on edit file.

Medicare coverage articles

No current Billing and Coding Article lists A9591 in its HCPCS table. Coverage then follows the drug's FDA label, compendia and any National Coverage Determination; check the Medicare Coverage Database before administering off-label.

Hospital outpatient (OPPS) status

In the October 2026 OPPS Addendum B, A9591 carries status indicator K and is assigned to APC 9370, with a published national unadjusted payment of $460.42. Status K means the drug is paid separately under OPPS rather than packaged into the procedure.

Ambulatory surgical center (ASC) payment

In the October 2026 ASC Addendum BB (covered ancillary services), A9591 carries payment indicator K2, which CMS defines as "Drugs, biologicals, and radiopharmaceuticals paid separately when provided integral to a surgical procedure on ASC list; payment based on OPPS rate". The national ASC payment is $460.42 per 1 millicurie, paid only when the drug is furnished integral to a covered surgical procedure.

Common denials for A9591 and how to prevent them

CARC 16 · M119

NDC missing, invalid or not matched to the HCPCS code

CARC 151 · N362

units billed exceed the MUE for the date of service

CARC 50 · N115

diagnosis not covered by the applicable coverage article or LCD

How QuickIntell checks A9591 before the claim leaves

QuickCode validates the NDC-to-unit conversion against the current OPPS NDC-HCPCS crosswalk, checks units against every published MUE setting and flags PTP and add-on conflicts on the same claim. QuickRCM routes CARC 16, 151 and 50 denials on drug lines with the matching coverage article attached so the appeal starts with evidence.

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Frequently asked questions — HCPCS A9591

What does HCPCS code A9591 describe?

A9591 is defined by CMS as "Fluoroestradiol f 18, diagnostic, 1 millicurie". Each billing unit represents 1 millicurie, so the units reported on the claim must equal the dose administered divided by that unit.

Is A9591 a CPT code?

No. A9591 is a HCPCS Level II code, the letter-plus-four-digit set CMS maintains for drugs such as fluoroestradiol f 18; CPT codes are five-character codes maintained by the AMA. On a Part B claim A9591 reports the drug itself in 1 millicurie units, and the administration is billed on its own line.

What does Medicare pay for A9591 in a hospital outpatient department?

A9591 has no Part B ASP limit; the October 2026 OPPS Addendum B pays it separately under status K, APC 9370, at $460.42 per 1 millicurie, and ASC Addendum BB gives it payment indicator K2 at $460.42.

How many units of A9591 can be billed per day?

The practitioner Medically Unlikely Edit is 6 units per date of service with adjudication indicator 3 (Date of Service Edit: Clinical). MAI 3 edits can be appealed with documentation that the units were medically reasonable. CMS cites "Prescribing Information" as the rationale.

Does A9591 have NCCI bundling edits?

No active practitioner PTP pairs list A9591 as a column-1 or column-2 code in the v323r0 release.

Sources

Every figure on this page is taken from the CMS publications below, as released by the Centers for Medicare & Medicaid Services. Projection built 2026-10-10. Verify against the primary file before billing or contracting decisions. The reference methodology explains how each figure is computed from these files.

Disclaimer

This page is an operational reference compiled from CMS publications: the Medicare Part B drug payment limit and NDC crosswalk files, NCCI MUE and add-on edit tables, aggregate PTP statistics, OPPS Addendum B, ASC Addendum BB and the Medicare Coverage Database. Payment limits and rates are Medicare national amounts; commercial and Medicaid payers differ. CPT codes are shown as numbers only; CPT descriptors are copyright AMA. Nothing here is legal, clinical or billing advice.

Found a figure that does not match the CMS file? Report a data correction with the CMS file and the value you expected; the request reaches the editorial team through the contact form.