I40
ICD-10Non-billable categoryAcute myocarditis
Official ICD-10-CM descriptor (FY2026)
Acute myocarditis
I40 is a category heading, not a billable code. CMS does not accept it on a claim; report one of the more specific codes beneath it.
Includes
- subacute myocarditis
Excludes1
Not coded here. An Excludes1 code should never be reported at the same time as the code above it.
- acute rheumatic myocarditis (I01.2)
More specific codes under I40
Where this code sits
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ICD-10-CM FY2026. Centers for Medicare & Medicaid Services (CMS) / National Center for Health Statistics (NCHS), “2026 ICD-10-CM Code Descriptions in Tabular Order” (icd10cm_order_2026.txt). Download the original file from cms.gov. Public domain (US Government work). Descriptors, billable flags and instructional notes on this page are reproduced from that file without modification. Krasyn adds no clinical guidance.