ICD-10 Code I48.9 – Unspecified atrial fibrillation and atrial flutter (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code I48.9 – Unspecified atrial fibrillation and atrial flutter
What it is
I48.9 identifies atrial fibrillation or atrial flutter when the record does not specify the type. Use it for an atrial arrhythmia documented without enough detail for a more exact code.
Clinical signs
Patients may have an irregular or rapid pulse, palpitations, shortness of breath, dizziness, or fatigue. Clinical features vary; refer to documentation.
When to use this code
Use I48.9 when the provider documents atrial fibrillation, atrial flutter, or both, but does not identify a specific subtype. It is also appropriate when the note lacks enough detail to code a more specific atrial arrhythmia. Check documentation if the record suggests a distinct type elsewhere.
Do not use for
Do not use I48.9 when the chart clearly states a specific atrial fibrillation or flutter type, such as persistent, paroxysmal, or chronic. Do not use it for other supraventricular arrhythmias.
Coding tip
Query the provider when the rhythm type is unclear, because a more specific I48 code may be supported.