2026 ICD-10-CM Diagnosis Code I40Acute myocarditis

ICD-10-CM Codes›I00–I99›I30-I5A›I40

ICD-10-CM I40
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

I40 is a non-billable ICD-10-CM category code for acute myocarditis, so it cannot be submitted on claims. Use a more specific code from this category instead, such as I40.0, I40.1, I40.8, and I40.9.

Code Identity

ICD-10-CM Code
I40
Billable Status
No — Non-Billable Category
Code Describes
Acute myocarditis
Chapter
I30-I5A
Other forms of heart disease

Code Classification

ChapterI00–I99Diseases of the circulatory system
SectionI30-I5AOther forms of heart disease
CategoryI40Acute myocarditis
This CodeI40Acute myocarditis

Specific Coding for Acute myocarditisOverview

Non-specific codes like I40 require more characters. Use one of these billable codes instead:

  • Use I40.0 for Infective myocarditis

  • Use I40.1 for Isolated myocarditis

  • Use I40.8 for Other acute myocarditis

  • Use I40.9 for Acute myocarditis, unspecified

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Includes

  • subacute myocarditis

Type 1 Excludes

  • acute rheumatic myocarditis I01.2

Clinical InformationClinical

  • Acute Myocarditis

    the sudden onset of inflammation of heart muscle with myocellular necrosis; this is generally secondary to an infectious cause, and patients often have a recent history of a flu-like illness.

Patient EducationClinical

Cardiomyopathy

Cardiomyopathy is the name for diseases of the heart muscle. These diseases enlarge your heart muscle or make it thicker and more rigid than normal. In rare cases, scar tissue replaces the muscle tissue.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About I40Overview

Is I40 (Acute myocarditis) a billable code?

No. This is a category header that groups the codes for acute myocarditis, and headers cannot be submitted on claims. Claims for acute myocarditis need a more specific code from this category, such as I40.0, I40.1, and I40.8.