ICD-10 Code J21 – Acute bronchiolitis (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code J21 – Acute bronchiolitis
What it is
J21 identifies acute bronchiolitis, an acute inflammatory illness of the small airways in the lungs. Use it when documentation states bronchiolitis without a more specific organism or subtype.
Clinical signs
Typical findings include cough, wheezing, tachypnea, and increased work of breathing, especially in infants and young children. Clinical features vary; refer to documentation.
When to use this code
Use J21 when the provider documents acute bronchiolitis as the diagnosis and does not specify a more detailed ICD-10 option. It is appropriate for encounter coding when the record supports an acute lower respiratory infection centered in the bronchioles. If the note names a specific cause or subtype, code to that documented detail instead.
Do not use for
Do not use J21 for chronic bronchiolitis or for bronchiolitis with a documented different primary diagnosis. Check documentation if the record instead describes bronchiolitis obliterans or another specific condition.
Coding tip
Assign the most specific bronchiolitis code supported by the note, and verify whether the provider documented an organism or other qualifying detail.