ICD-10-CM 2027 diagnosis code

I40Acute myocarditis

Not billable — use a more specific code

I40 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 I40

I40 is the ICD-10-CM diagnosis code for acute myocarditis. It belongs to 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 4 subcodes must be used instead.

To report this condition, pick the subcode that matches the documentation: I40.0 (myocarditis), I40.1 (myocarditis), I40.8 (myocarditis) and I40.9 (unspecified).

Don't report I40 together with the conditions in its Excludes1 note: acute rheumatic myocarditis (I01.2).

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 I40

Coding notes

IncludesFurther defines the content of the category

subacute myocarditis

Excludes1Not coded here — never report together with this code

acute rheumatic myocarditis (I01.2)

Notes that apply from higher levels

Instructions written at a parent level also apply to I40.

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

Codes whose notes reference I40

I51.4Excludes1
I5ACode first
M35.81Code also

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 I40

Is I40 billable?: No. I40 is a header code. Report one of its more specific subcodes instead.