ICD-10-CM 2027 diagnosis code

J21Acute bronchiolitis

Not billable — use a more specific code

J21 is a header code, so it can't be reported by itself. Choose one of the 4 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 J21

J21 is the ICD-10-CM diagnosis code for acute bronchiolitis. It belongs to block J20-J22 (other acute lower respiratory infections) and chapter 10 (diseases of the respiratory system). It is a header code, so it can't be reported by itself; one of its 4 subcodes must be used instead.

To report this condition, pick the subcode that matches the documentation: J21.0 (due to respiratory syncytial virus), J21.1 (due to human metapneumovirus), J21.8 (due to other specified organisms) and J21.9 (unspecified).

The conditions in its Excludes2 note aren't part of J21, but may be coded alongside it if the patient has both: respiratory bronchiolitis interstitial lung disease (J84.115).

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 J21

Coding notes

IncludesFurther defines the content of the category

acute bronchiolitis with bronchospasm

Excludes2Not included here — may be reported together if both conditions exist

respiratory bronchiolitis interstitial lung disease (J84.115)

Notes that apply from higher levels

Instructions written at a parent level also apply to J21.

Broader instructions also apply from J20-J22 Other acute lower respiratory infections and Chapter 10: Diseases of the respiratory system.

Codes whose notes reference J21

J18.0Excludes2
J98.01Excludes1

Code history

2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027

FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
No changes since FY2016.

Common questions about J21

Is J21 billable?: No. J21 is a header code. Report one of its more specific subcodes instead.