HCPCS Code A9585: Gadobutrol Injection Billing Guide

Key Takeaways

HCPCS code A9585 describes Injection, gadobutrol, 0.1 mL (brand name Gadavist), used for MRI contrast enhancement.

Bill A9585 with revenue code 636 in outpatient hospital settings; omitting either HCPCS code or units triggers a claim edit.

Coverage status is carrier judgment, meaning each Medicare contractor and commercial payer decides coverage individually.

Pabau’s claims management software supports radiology billing workflows, helping reduce coding errors before submission.

Gadolinium-based contrast agents are among the most frequently billed radiopharmaceuticals in outpatient hospital coding, yet gadobutrol claims still generate avoidable denials. The most common triggers: missing revenue code 636, incorrect unit counts, and selecting the wrong code when A9579 (the not-otherwise-classified contrast agent code) would not apply. This guide covers HCPCS code A9585 from code description through documentation requirements, so your radiology billing team has a single reference for clean claims.

This reference covers code description and short name, clinical indications, billing with revenue code 636, units calculation, Medicare and Medicaid coverage, applicable modifiers, related HCPCS codes, NDC crosswalk requirements, and documentation standards.

HCPCS Code A9585: Description, Short Name, and Code Properties

HCPCS code A9585 has the following official properties, as maintained by CMS under the Healthcare Common Procedure Coding System:

Gadobutrol is a macrocyclic gadolinium-based contrast agent (GBCA) manufactured by Bayer AG under the brand name Gadavist. The 0.1 mL billing unit is the defining feature of A9585 and drives how units are counted on the claim. Each 0.1 mL administered equals one billable unit.

Clinical Indications for Gadobutrol (Gadavist)

Gadobutrol is FDA-approved for contrast-enhanced MRI of the central nervous system, body, and vasculature in adults and pediatric patients. Radiologists and ordering physicians use it to improve detection and characterization of lesions with disrupted blood-brain barriers or abnormal vascularity. Common clinical scenarios where A9585 appears on claims include brain and spinal cord MRI with contrast, vascular MRI (MRA), cardiac MRI, and body MRI for lesion characterization.

Gadobutrol is macrocyclic rather than linear, a distinction that matters for clinical risk discussions around gadolinium retention. For billing purposes, the relevant clinical context is medical necessity: the ordering physician’s documentation must support why contrast enhancement was required for the specific MRI study. Supporting structured clinical documentation at your practice reduces the risk of medical necessity denials on contrast agent claims.

Common MRI CPT Codes Paired with A9585

• 70553 – MRI brain with and without contrast
• 71552 – MRI chest with and without contrast
• 72157 – MRI thoracic spine with and without contrast
• 73223 – MRI upper extremity with and without contrast
• 74183 – MRI abdomen with and without contrast

The MRI CPT code and A9585 appear on the same claim to represent the procedure and the contrast drug, respectively. NCCI edits and bundling rules are subject to quarterly updates; verify current edits before submitting combined claims.

Billing HCPCS Code A9585 with Revenue Code 636

Revenue code 636 is the pairing requirement that trips up many radiology billers. According to CMS Billing and Coding Guidelines for Magnetic Resonance Imaging (LCD Attachment L28723): when administering an MRI contrast agent, bill HCPCS code A9579 or A9585 with revenue code 636. When a claim is received with a 636 revenue code, both a HCPCS code and units must be present. If either is missing, the claim is subject to a claim edit.

Revenue code 636 is designated for drugs paid at a rate other than cost, which is how contrast agents and radiopharmaceuticals are reimbursed in the outpatient hospital setting. This differs from revenue code 250 (pharmacy general classification) and 258 (IV solutions), which are used for other drug types. Your claims management workflow should flag any 636-coded line missing a HCPCS code or unit count before the claim reaches the payer.

Units Calculation: How Many Units to Bill

Each unit of A9585 equals 0.1 mL of gadobutrol administered. To calculate billable units, divide the total volume administered (in mL) by 0.1. A standard adult dose of Gadavist is 0.1 mmol/kg at a concentration of 1 mmol/mL, meaning a 70 kg patient typically receives 7 mL, which equals 70 units of A9585.

Billing partial units is not permitted. Round to the nearest whole unit. Some payers may impose a maximum unit limit per claim; verify with the individual carrier before submitting high-volume doses.

Medicare and Medicaid Coverage for A9585

Medicare coverage for HCPCS code A9585 is carrier judgment, confirmed by HIPAASpace, ndclist.com, and multiple coding registries. Carrier judgment means each Medicare Administrative Contractor (MAC) decides coverage individually based on local coverage determinations (LCDs) and the clinical documentation submitted. Coverage is not universally guaranteed across all contractors or all indications.

For Medicare Part B billing in the physician office setting, A9585 is reimbursed under the buy-and-bill model at Average Sales Price (ASP) plus a percentage add-on. ASP rates are updated quarterly by CMS; always verify the current rate at the time of service using the CMS Physician Fee Schedule. Outpatient hospital settings are reimbursed under the Outpatient Prospective Payment System (OPPS), which uses Ambulatory Payment Classification (APC) rates.

State Medicaid programs vary. Some states, including North Carolina (NCDHHS) and West Virginia (WV MMIS), have issued specific provider bulletins addressing A9585 billing. Check your state Medicaid fee schedule and any applicable prior authorization requirements before billing. For practices managing multiple payer types, centralising procedure code and drug billing workflows reduces the risk of payer-specific rule violations.

Prior Authorization Considerations

Prior authorization requirements for A9585 vary significantly by payer. Commercial payers such as UnitedHealthcare (Oxford Health Plans) publish radiopharmaceuticals and contrast media policies that specify which GBCAs require prior authorization and under which clinical conditions. As of December 2025, UnitedHealthcare’s policy lists A9585 among covered contrast agents subject to medical necessity documentation requirements.

Always check the individual payer’s prior authorization lookup tool before scheduling a contrast-enhanced MRI study for non-emergency cases. Documenting the authorization number in the patient’s record and on the claim reduces denial risk for prior-authorization-required payers.

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A9585 vs A9579: Choosing the Right HCPCS Code

HCPCS code A9579 (Injection, gadolinium-based magnetic resonance contrast agent, not otherwise classified) is the generic catch-all code for MRI contrast agents that do not have their own specific HCPCS code. A9585 is the product-specific code for gadobutrol (Gadavist). When gadobutrol is administered, A9585 should always be billed rather than A9579.

Using A9579 when A9585 applies may result in lower reimbursement, as payers may apply different payment rates for NOS codes. Some payers also deny A9579 when a product-specific code exists and the drug administered is identifiable. Coding accuracy here directly affects revenue. Practices managing injection and infusion billing workflows benefit from a code reference that maps specific drugs to their HCPCS codes.

Modifiers Applicable to HCPCS Code A9585

Modifiers for A9585 are applied based on the billing setting and clinical circumstances, not as part of routine contrast agent billing. The following modifiers may apply in specific scenarios:

• Modifier JW – Drug amount discarded/not administered to any patient. Required by many payers when a portion of a single-dose vial is wasted. Document waste in the administration record.
• Modifier JZ – Zero drug waste (no discarded drug). Required by some payers as a companion to modifier JW compliance; indicates full vial use with no waste.
• Modifier GY – Item or service statutorily excluded. Used when billing a non-covered service for a Medicare Advance Beneficiary Notice (ABN).
• Modifier 59 – Distinct procedural service. May apply when A9585 is billed alongside another drug code on the same date of service and NCCI edits require unbundling documentation.
• Modifier Q0 – Investigational clinical service provided in a clinical research study. Used when the MRI is part of an approved clinical trial.

Modifier JW and JZ requirements vary by payer. Medicare Part B and many commercial payers require documentation of drug waste in the medical record when JW is appended. Verify the specific modifier policy with each contracted payer. Practices handling drug administration billing can review procedure code billing guidance for additional modifier application context.

NDC Crosswalk and Reporting Requirements for A9585

Many payers, including most commercial payers and some state Medicaid programs, require National Drug Code (NDC) reporting on claims for drugs billed under HCPCS codes like A9585. The NDC identifies the specific product, manufacturer, and package size. For Gadavist (gadobutrol), the NDC corresponds to Bayer’s registered product codes.

NDC reporting requirements on professional claims (CMS-1500) differ from institutional claims (UB-04). On a CMS-1500, the NDC is typically reported in the shaded area of Box 24 using the qualifier N4, the 11-digit NDC, the unit qualifier, and the quantity administered. On a UB-04, NDC information is usually reported in the drug detail lines associated with the revenue code 636 line. Always confirm the payer-specific NDC reporting format before submitting. Using digital documentation tools that capture drug administration details at the point of care makes NDC extraction accurate and audit-ready.

For HCPCS code lookup and NDC crosswalk data, the AAPC Codify HCPCS lookup and PGM Billing’s free HCPCS tool both support NDC crosswalk queries for A-series codes including A9585.

Documentation Requirements to Support Medical Necessity

Medical necessity documentation for A9585 claims must link the contrast administration to a clinical indication supported by ICD-10 diagnosis codes. The ordering physician’s notes should capture the reason contrast was required, the body area imaged, and the clinical question the MRI was intended to answer. Radiology reports that describe contrast enhancement findings add further support.

Commonly paired ICD-10 codes include those for neoplasms (C71.x for brain tumors), demyelinating diseases (G35 for multiple sclerosis), cerebrovascular conditions, and musculoskeletal lesions requiring soft tissue characterization. The specific ICD-10 code must match the clinical documentation; avoid using a code that is not supported by the visit notes. Practices with high-volume radiology coding can benefit from structured procedure code workflows that standardize how supporting diagnosis codes are selected and validated before claim submission.

Setting-Specific Documentation Notes

• Outpatient hospital: MRI order with contrast indication, radiology report, nursing/tech administration record documenting dose and time, revenue code 636 line on UB-04 with A9585 and units.
• Physician office (in-office MRI): Physician order, clinical note supporting contrast necessity, drug administration record with NDC, A9585 on CMS-1500 with NDC in Box 24.
• Independent imaging center: Referral/order documentation, administration log, radiology report, applicable LCD criteria met and documented.

Expert Picks

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Looking for HCPCS procedure code references beyond A-series codes? Pabau’s CCSD and Procedure Code Guide covers billing code structures across multiple systems relevant to imaging and procedure billing.

Managing injection and infusion drug billing alongside contrast agents? Best EMR for IV Therapy reviews practice management tools suited to drug administration billing workflows.

Conclusion

HCPCS code A9585 claims fail most often because of two preventable errors: missing revenue code 636 on outpatient hospital claims and incorrect unit counts based on administered volume. Getting both right requires a billing workflow that connects the drug administration record to the claim before submission.

Pabau’s claims management software helps radiology and imaging practices catch these errors at the source, supporting accurate HCPCS billing and reducing denials on contrast agent claims. To see how Pabau supports radiology billing workflows, book a demo.

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