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M55 Remark Code: Anti-Emetic Without Oral Anti-Cancer Drug

M55 means the payer does not cover this self-administered anti-emetic drug on its own. It is only payable when administered together with a covered oral anti-cancer drug.

Quick facts

Code
M55 (RARC M55)
Status
Active In use since January 1, 1997.
Code set
Remittance Advice Remark Codes (RARC)
Group codes
  • CO (Contractual Obligation): The supplier absorbs the amount unless the patient was properly notified in advance.
  • PR (Patient Responsibility): The patient is responsible when a valid advance notice was signed before the drug was supplied.
Official description
We do not pay for self-administered anti-emetic drugs that are not administered with a covered oral anti-cancer drug.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What M55 means

Medicare Part B generally does not pay for drugs patients take on their own at home. There are narrow exceptions, and oral anti-emetics tied to cancer treatment are one of them. M55 says the anti-emetic on this claim was not linked to a covered oral anti-cancer drug, so the exception did not apply.

It is a Medicare-specific remark, usually seen on DME contractor or pharmacy supplier claims.

Common causes

  • The patient is not receiving a covered oral anti-cancer drug.
  • The claim did not include the diagnosis or indicators linking the two drugs.
  • The anti-emetic was prescribed for nausea unrelated to cancer treatment.
  • Timing or quantity did not match the anti-cancer regimen.

How to fix it

  1. Confirm the patient’s cancer treatment and whether it includes a covered oral anti-cancer drug.
  2. If the link exists, correct diagnosis codes (box 21) and required modifiers, then resubmit with resubmission code 7, or appeal with supporting records.
  3. If the link does not exist, bill the patient’s prescription drug plan where appropriate, or the patient if a valid advance notice was signed.

How to prevent it

Verify the anti-cancer regimen at intake for every anti-emetic order and review the DME contractor’s policy for required claim elements. For how remark codes point to coverage rules, see CARC and RARC denial analysis.

Codes that may appear with M55

  • CO-96 (Non-covered charge(s).): The drug is non-covered in this circumstance.
  • CO-50 (These are non-covered services because this is not deemed a 'medical necessity' by the payer.): The drug was not deemed medically necessary under the payer's criteria.
  • CO-11 (The diagnosis is inconsistent with the procedure.): The diagnosis does not match the coverage requirement for the anti-emetic.
  • M100 (We do not pay for an oral anti-emetic drug that is not administered for use immediately before, at, or within 48 hours of administration of a…): An oral anti-emetic is not paid unless given within the required time frame around covered chemotherapy.
  • N569 (Not covered when performed for the reported diagnosis.): Not covered when performed for the reported diagnosis.
  • CO-96 (Non-covered charge(s).): The non-covered reason code that usually carries M55.

M55 FAQ

Why does coverage depend on another drug?

Under Medicare Part B, certain self-administered drugs are covered only in specific circumstances. For anti-emetics, the benefit is tied to anti-cancer treatment rather than general nausea.

Could the drug be covered under a different benefit?

Possibly. Self-administered drugs not covered under Part B may fall under the patient's prescription drug plan. Check the patient's coverage.

How do I show the link to anti-cancer treatment?

Use the diagnosis codes, modifiers, and documentation the DME contractor requires for the anti-emetic benefit, and keep the chemotherapy details in the record.