Acute and subacute endocarditis (I33) ICD-10-CM
The I33 code range covers acute and subacute endocarditis with 3 ICD-10-CM diagnosis codes. 2 of them are billable and valid for claim submission in fiscal year 2026, and the category headers group them but cannot themselves be billed.
Type 1 Excludes
A type 1 excludes note is a pure excludes note. It means "NOT CODED HERE!" An Excludes1 note indicates that the code excluded should never be used at the same time as the code above the Excludes1 note. An Excludes1 is used when two conditions cannot occur together, such as a congenital form versus an acquired form of the same condition.
Codes in the I33 Range 3 codes · 2 billable
About the I33 Code Range
The ICD-10 codes I33, including I33.0 and I33.9, are used to classify acute and subacute forms of endocarditis, an infection or inflammation of the heart's inner lining and valves. These codes help identify cases of infective and unspecified endocarditis in medical records and billing.
I33.0 specifically covers acute and subacute infective endocarditis, also known by several synonyms such as acute bacterial endocarditis, vegetative endocarditis, and infective endocarditis of cardiac valves with vegetation. This code applies when the infection involves heart valves like the aortic, mitral, tricuspid, or pulmonary valves and may include complications like abscesses, embolism, or valve vegetations. It addresses infections caused by bacteria, fungi (e.g., blastomycosis), or rickettsial organisms, and is used for both native and prosthetic heart valves. People searching for the ICD-10 code for infective endocarditis will find this code relevant.
I33.9 is for acute and subacute endocarditis when the specific cause or infective agent is not known or unspecified. It also includes non-infective or myoendocarditis and related conditions like abscesses of cardiac septa or heart inflammation co-occurring with HIV infection. Coders use this code when clinical details are not sufficient to assign a more specific diagnosis.
Questions About This Page
How many billable codes are in the I33 range?
Of the 3 codes in this range, 2 are billable and valid for claim submission from October 1, 2025 through September 30, 2026. Category header codes group them but cannot be reported on claims.
What does the I33 range classify?
The range classifies acute and subacute endocarditis. Each code links to its own reference page with billing status, MS-DRG grouping, coding notes, and clinical information.
Related References
Source: CMS FY 2026 ICD-10-CM Tabular List and order file, effective October 1, 2025 through September 30, 2026.
