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ICD-10-CM 2027 diagnosis code

I48.9Unspecified atrial fibrillation and atrial flutter

Not billable — use a more specific code

I48.9 is a header code, so it can't be reported by itself. Choose one of the 2 more specific codes beneath it.

Code unchanged since ICD-10-CM took effect on October 1, 2015. Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data

About I48.9

I48.9 is the ICD-10-CM diagnosis code for unspecified atrial fibrillation and atrial flutter. It belongs to category I48 (atrial fibrillation and flutter), block I30-I5A (other forms of heart disease) and chapter 9 (diseases of the circulatory system). It is a header code, so it can't be reported by itself; one of its 2 subcodes must be used instead.

Within I48, choose I48.9 (Unspecified atrial fibrillation and atrial flutter) only when documentation doesn't support a more specific option: paroxysmal atrial fibrillation (I48.0), persistent atrial fibrillation (I48.1), chronic atrial fibrillation (I48.2), Typical atrial flutter (I48.3) and atypical atrial flutter (I48.4).

To report this condition, pick the subcode that matches the documentation: I48.91 (fibrillation) and I48.92 (flutter).

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Specific codes under I48.9

Notes that apply from higher levels

Instructions written at a parent level also apply to I48.9.

Broader instructions also apply from Chapter 9: Diseases of the circulatory system.

Code history

  1. 2016
  2. 2017
  3. 2018
  4. 2019
  5. 2020
  6. 2021
  7. 2022
  8. 2023
  9. 2024
  10. 2025
  11. 2026
  12. 2027
  • FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
  • No changes since FY2016.

Common questions about I48.9

Is I48.9 billable?

No. I48.9 is a header code. Report one of its more specific subcodes instead.