2027 ICD-10-CM Diagnosis Code I40Acute myocarditis

ICD-10-CM Codes›I00–I99›I30-I5A›I40

ICD-10-CM I40
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

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
Short Description
Acute myocarditis
Same as the full description in the CMS dataset.
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

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to I40: its own notes plus those printed at Chapter 9. A note printed at a category, block or chapter applies to every code under it.

Includes

Further defines, or gives examples of, the content of the category.

  • subacute myocarditis

Excludes1

Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.

  • acute rheumatic myocarditis (I01.2)

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From Chapter 9 (I00-I99) Diseases of the circulatory system applies to 1,433 codes
  • certain conditions originating in the perinatal period (P04-P96)
  • certain infectious and parasitic diseases (A00-B99)
  • complications of pregnancy, childbirth and the puerperium (O00-O9A)
  • congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
  • endocrine, nutritional and metabolic diseases (E00-E88)
  • injury, poisoning and certain other consequences of external causes (S00-T88)
  • neoplasms (C00-D49)
  • symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)
  • systemic connective tissue disorders (M30-M36)
  • transient cerebral ischemic attacks and related syndromes (G45.-)

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name I40, its category, or a range that includes it.

Excludes1 1

These codes carry an Excludes1 note naming I40: they are not reported together with it, unless the two conditions are unrelated.

  • I51.4 Myocarditis, unspecified
    acute or subacute myocarditis (I40.-)

Code First 1

These codes say to code first a condition named in the note, and I40 is one of the conditions named.

  • I5A Non-ischemic myocardial injury (non-traumatic)
    acute myocarditis (I40.-)

Code Also 1

These codes say I40 may also be needed to fully describe the condition. The note gives no sequencing direction.

  • M35.81 Multisystem inflammatory syndrome
    acute myocarditis (I40.-)

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 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About I40Overview

What is the ICD-10 code for acute myocarditis?

I40 is the ICD-10-CM category for acute myocarditis, but it is a non-billable header: claims need a more specific code from this category, listed on this page.

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.

Can I40 be reported with I01.2?

Not as a rule. The Excludes1 note on I40 lists "acute rheumatic myocarditis (I01.2)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).