ICD-10 Code I48 – Atrial fibrillation and flutter (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code I48 – Atrial fibrillation and flutter
What it is
I48 identifies atrial fibrillation, atrial flutter, or both when documented together. These are supraventricular arrhythmias in which the atria beat abnormally fast or irregularly.
Clinical signs
Common findings include an irregular pulse, palpitations, fatigue, shortness of breath, or dizziness. Clinical features vary; refer to documentation for the specific rhythm, onset, and whether the episode is paroxysmal, persistent, or chronic.
When to use this code
Use I48 when the provider documents atrial fibrillation, atrial flutter, or both as the diagnosis being treated or evaluated. It may also fit when the record clearly identifies an atrial arrhythmia without a more specific subcode in the note. Check documentation if the chart distinguishes a postoperative, transient, or secondary rhythm disturbance.
Do not use for
Do not use I48 for other arrhythmias such as atrial tachycardia, premature beats, or ventricular dysrhythmias. If the record only says “irregular heartbeat” without a confirmed diagnosis, check documentation.
Coding tip
Capture the exact rhythm term and episode type from the provider note before selecting the most specific I48 code.